Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-10 Thread Eric Voskuil
Martin,

I like your idea for the commit protocol in that it resolves the
vandalous address substitution attack. However, I don't see a way to
prevent privacy loss without adverse impact to the scenario.

Anyone could perform the handshake and thereby obtain the payment
request. Therefore to prevent inadvertent disclosure the customer must
visually confirm the phrase and then verbally tell the merchant to
proceed by sending the payment request.

One might argue that it's sufficient to preserve the integrity of the
transaction while suffering the privacy loss, especially given that a
hijacked handshake should never result in a completed transaction -
unless of course the hijacker pays.

But imagine someone purchasing their meds. HIPAA requires the checkout
queue to form behind a yellow line. That speaks directly to this question.

e

On 02/06/2015 01:07 AM, MⒶrtin HⒶboⓋštiak wrote:
 2015-02-06 2:29 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 04:36 PM, Martin Habovštiak wrote:
 I believe, we are still talking about transactions of physical
 people in physical world. So yes, it's proximity based - people
 tell the words by mouth. :)

 Notice from my original comment:

 A MITM can substitute the key. If you don't have verifiable
 identity associated with the public key (PKI/WoT), you need
 a shared secret (such as a secret phrase).

 I said this could only be accomplished using a shared secret or a
 trusted public key. Exchanging a value that is derived from a pair of
 public keys is a distinction without a difference. The problem remains
 that the parties must have a secure/out-of-band channel for
 communicating this value.

 The fact that they are face-to-face establishes this channel, but that
 brings us back to the original problem, as it requires manual
 verification - as in visual/audible scanning of the two values for
 comparison. At that point the visual comparison of the address, or some
 value derived from it, is simpler.
 
 I have never been against manual verification. What I'm trying to say
 is let's just make manual verification easier and more secure.
 Comparison of address is simpler for the coder but also simpler to
 attack. It has these problems:
 - Addresses broadcasted in plaintext (privacy issue)
 - Amounts broadcasted in plaintext (privacy issue)
 - Address is long - takes lot of time to verify (user experience issue)
 - Address prefix can be brute-forced, if too short or used to make
 black hole address if longer (vandalism issue)
 
 Commit protocol can be used for both the encryption and the
 authentication while user experience is not bad and everything is
 still secure.
 

 In case of RedPhone, you read those words verbally over not-yet-
 verified channel relying on difficulty of spoofing your voice. Also
 the app remembers the public keys, so you don't need to verify
 second time.

 This is reasonable, but wouldn't help in the case of an ad-hoc
 connection between parties who don't know each other well.

 I suggest you to try RedPhone (called Signal on iPhone) yourself.
 It's free/open source, Internet-based and end-to-end encrypted. You
 may find it useful some day. Also I'm willing to help you with
 trying it after I wake up. (~8 hours: Send me private e-mail if
 you want to.)

 I appreciate the offer. I really don't trust *any* smartphone as a
 platform for secure communication/data. But encrypting on the wire does
 of course shrink the attack surface and increase the attacker's cost.

 e

 Dňa 6. februára 2015 1:22:23 CET používateľ Eric Voskuil
 e...@voskuil.org napísal:

 On 02/05/2015 04:04 PM, MⒶrtin HⒶboⓋštiak wrote:
 That's exactly what I though when seeing the RedPhone code, but after
 I studied the commit protocol I realized it's actually secure and
 convenient way to do it. You should do that too. :)

 I was analyzing the model as you described it to me. A formal analysis
 of the security model of a particular implementation, based on
 inference
 from source code, is a bit beyond what I signed up for. But I'm
 perfectly willing to comment on your description of the model if you
 are
 willing to indulge me.

 Shortly, how it works:
 The initiator of the connection sends commit message containing the
 hash of his temporary public ECDH part, second party sends back their
 public ECDH part and then initiator sends his public ECDH part in
 open. All three messages are hashed together and the first two bytes
 are used to select two words from a shared dictionary which are
 displayed on the screen of both the initiator and the second party.

 The parties communicate those two words and verify they match.

 How do they compare words if they haven't yet established a secure
 channel?

 If an attacker wants to do MITM, he has a chance of choosing right
 public parts 1:65536. There is no way to brute-force it, since that
 would be noticed immediately. If instead of two words based on the
 first two bytes, four words from BIP39 wordlist were chosen, it would
 provide 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-10 Thread Eric Voskuil
On 02/10/2015 09:16 AM, MⒶrtin HⒶboⓋštiak wrote:
 I'm not sure if I was clear enough. Handshake should be used to
 establish authenticated AND encrypted communication using ECDH (or
 just DH, but I think it's easier to use ECDH, since required functions
 are already used in Bitcoin protocol), like RedPhone does. BTW
 knowledge of verification string is useless to the attacker.

Yes, I think this was clear from your description.

 Yes, the customer must verify it verbally and the merchant shouldn't
 send the transaction before verification. Other possibility is that in
 case of differing verification strings new address is generated, so
 attacker doesn't know the address. But in this case, amount is leaked
 and there is quite high probability it can be found in the Blockchain.

Yes, for each handshake the payment request would need to contain a
different address, mitigating some of the privacy loss.

 Anyway, I don't believe the transaction can be made securely without
 such interaction except with white-listing public keys, so I see no
 reason why interaction should be problematic.

It can be done securely and privately by transfer of a shared secret
through a private channel.

 We don't have such strict regulations but I agree that security is
 important. Currently I think that verbal verification and manual
 confirmation is the best way to achieve high security and reasonable
 user-friendliness.

I think for a broadcast model (e.g. Bluetooth only) that is the only
want to ensure integrity and privacy. A narrow cast can use proximity to
establish trust.

 2015-02-10 17:55 GMT+01:00 Eric Voskuil e...@voskuil.org:
 Martin,

 I like your idea for the commit protocol in that it resolves the
 vandalous address substitution attack. However, I don't see a way to
 prevent privacy loss without adverse impact to the scenario.

 Anyone could perform the handshake and thereby obtain the payment
 request. Therefore to prevent inadvertent disclosure the customer must
 visually confirm the phrase and then verbally tell the merchant to
 proceed by sending the payment request.

 One might argue that it's sufficient to preserve the integrity of the
 transaction while suffering the privacy loss, especially given that a
 hijacked handshake should never result in a completed transaction -
 unless of course the hijacker pays.

 But imagine someone purchasing their meds. HIPAA requires the checkout
 queue to form behind a yellow line. That speaks directly to this question.

 e

 On 02/06/2015 01:07 AM, MⒶrtin HⒶboⓋštiak wrote:
 2015-02-06 2:29 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 04:36 PM, Martin Habovštiak wrote:
 I believe, we are still talking about transactions of physical
 people in physical world. So yes, it's proximity based - people
 tell the words by mouth. :)

 Notice from my original comment:

 A MITM can substitute the key. If you don't have verifiable
 identity associated with the public key (PKI/WoT), you need
 a shared secret (such as a secret phrase).

 I said this could only be accomplished using a shared secret or a
 trusted public key. Exchanging a value that is derived from a pair of
 public keys is a distinction without a difference. The problem remains
 that the parties must have a secure/out-of-band channel for
 communicating this value.

 The fact that they are face-to-face establishes this channel, but that
 brings us back to the original problem, as it requires manual
 verification - as in visual/audible scanning of the two values for
 comparison. At that point the visual comparison of the address, or some
 value derived from it, is simpler.

 I have never been against manual verification. What I'm trying to say
 is let's just make manual verification easier and more secure.
 Comparison of address is simpler for the coder but also simpler to
 attack. It has these problems:
 - Addresses broadcasted in plaintext (privacy issue)
 - Amounts broadcasted in plaintext (privacy issue)
 - Address is long - takes lot of time to verify (user experience issue)
 - Address prefix can be brute-forced, if too short or used to make
 black hole address if longer (vandalism issue)

 Commit protocol can be used for both the encryption and the
 authentication while user experience is not bad and everything is
 still secure.


 In case of RedPhone, you read those words verbally over not-yet-
 verified channel relying on difficulty of spoofing your voice. Also
 the app remembers the public keys, so you don't need to verify
 second time.

 This is reasonable, but wouldn't help in the case of an ad-hoc
 connection between parties who don't know each other well.

 I suggest you to try RedPhone (called Signal on iPhone) yourself.
 It's free/open source, Internet-based and end-to-end encrypted. You
 may find it useful some day. Also I'm willing to help you with
 trying it after I wake up. (~8 hours: Send me private e-mail if
 you want to.)

 I appreciate the offer. I really don't trust *any* smartphone as a
 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-10 Thread MⒶrtin HⒶboⓋštiak
I'm not sure if I was clear enough. Handshake should be used to
establish authenticated AND encrypted communication using ECDH (or
just DH, but I think it's easier to use ECDH, since required functions
are already used in Bitcoin protocol), like RedPhone does. BTW
knowledge of verification string is useless to the attacker.

Yes, the customer must verify it verbally and the merchant shouldn't
send the transaction before verification. Other possibility is that in
case of differing verification strings new address is generated, so
attacker doesn't know the address. But in this case, amount is leaked
and there is quite high probability it can be found in the Blockchain.
Anyway, I don't believe the transaction can be made securely without
such interaction except with white-listing public keys, so I see no
reason why interaction should be problematic.

We don't have such strict regulations but I agree that security is
important. Currently I think that verbal verification and manual
confirmation is the best way to achieve high security and reasonable
user-friendliness.

2015-02-10 17:55 GMT+01:00 Eric Voskuil e...@voskuil.org:
 Martin,

 I like your idea for the commit protocol in that it resolves the
 vandalous address substitution attack. However, I don't see a way to
 prevent privacy loss without adverse impact to the scenario.

 Anyone could perform the handshake and thereby obtain the payment
 request. Therefore to prevent inadvertent disclosure the customer must
 visually confirm the phrase and then verbally tell the merchant to
 proceed by sending the payment request.

 One might argue that it's sufficient to preserve the integrity of the
 transaction while suffering the privacy loss, especially given that a
 hijacked handshake should never result in a completed transaction -
 unless of course the hijacker pays.

 But imagine someone purchasing their meds. HIPAA requires the checkout
 queue to form behind a yellow line. That speaks directly to this question.

 e

 On 02/06/2015 01:07 AM, MⒶrtin HⒶboⓋštiak wrote:
 2015-02-06 2:29 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 04:36 PM, Martin Habovštiak wrote:
 I believe, we are still talking about transactions of physical
 people in physical world. So yes, it's proximity based - people
 tell the words by mouth. :)

 Notice from my original comment:

 A MITM can substitute the key. If you don't have verifiable
 identity associated with the public key (PKI/WoT), you need
 a shared secret (such as a secret phrase).

 I said this could only be accomplished using a shared secret or a
 trusted public key. Exchanging a value that is derived from a pair of
 public keys is a distinction without a difference. The problem remains
 that the parties must have a secure/out-of-band channel for
 communicating this value.

 The fact that they are face-to-face establishes this channel, but that
 brings us back to the original problem, as it requires manual
 verification - as in visual/audible scanning of the two values for
 comparison. At that point the visual comparison of the address, or some
 value derived from it, is simpler.

 I have never been against manual verification. What I'm trying to say
 is let's just make manual verification easier and more secure.
 Comparison of address is simpler for the coder but also simpler to
 attack. It has these problems:
 - Addresses broadcasted in plaintext (privacy issue)
 - Amounts broadcasted in plaintext (privacy issue)
 - Address is long - takes lot of time to verify (user experience issue)
 - Address prefix can be brute-forced, if too short or used to make
 black hole address if longer (vandalism issue)

 Commit protocol can be used for both the encryption and the
 authentication while user experience is not bad and everything is
 still secure.


 In case of RedPhone, you read those words verbally over not-yet-
 verified channel relying on difficulty of spoofing your voice. Also
 the app remembers the public keys, so you don't need to verify
 second time.

 This is reasonable, but wouldn't help in the case of an ad-hoc
 connection between parties who don't know each other well.

 I suggest you to try RedPhone (called Signal on iPhone) yourself.
 It's free/open source, Internet-based and end-to-end encrypted. You
 may find it useful some day. Also I'm willing to help you with
 trying it after I wake up. (~8 hours: Send me private e-mail if
 you want to.)

 I appreciate the offer. I really don't trust *any* smartphone as a
 platform for secure communication/data. But encrypting on the wire does
 of course shrink the attack surface and increase the attacker's cost.

 e

 Dňa 6. februára 2015 1:22:23 CET používateľ Eric Voskuil
 e...@voskuil.org napísal:

 On 02/05/2015 04:04 PM, MⒶrtin HⒶboⓋštiak wrote:
 That's exactly what I though when seeing the RedPhone code, but after
 I studied the commit protocol I realized it's actually secure and
 convenient way to do it. You should do that too. :)

 I was analyzing the model 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-06 Thread Roy Badami
 In this case there is no need for P2P communication, just pay to an
 address you already have for the other party. If you want to avoid
 address reuse, use stealth addressing.
 
 But yes, if you don't have a stealth address for the other party you can
 certainly communicate in private as peers where you trust that you share
 a public key. The core issue here is really bootstrapping of that trust
 in an ad hoc manner.

Something interactive might still be nicer, though, to avoid the risk
of paying to an address that the payee no longer has the private key
for.  Nooo!! Don't pay to that address.  I lost my old phone so I
generated a new wallet.

roy

--
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hub for all things parallel software development, from weekly thought
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-06 Thread MⒶrtin HⒶboⓋštiak
2015-02-06 2:29 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 04:36 PM, Martin Habovštiak wrote:
 I believe, we are still talking about transactions of physical
 people in physical world. So yes, it's proximity based - people
 tell the words by mouth. :)

 Notice from my original comment:

 A MITM can substitute the key. If you don't have verifiable
 identity associated with the public key (PKI/WoT), you need
 a shared secret (such as a secret phrase).

 I said this could only be accomplished using a shared secret or a
 trusted public key. Exchanging a value that is derived from a pair of
 public keys is a distinction without a difference. The problem remains
 that the parties must have a secure/out-of-band channel for
 communicating this value.

 The fact that they are face-to-face establishes this channel, but that
 brings us back to the original problem, as it requires manual
 verification - as in visual/audible scanning of the two values for
 comparison. At that point the visual comparison of the address, or some
 value derived from it, is simpler.

I have never been against manual verification. What I'm trying to say
is let's just make manual verification easier and more secure.
Comparison of address is simpler for the coder but also simpler to
attack. It has these problems:
- Addresses broadcasted in plaintext (privacy issue)
- Amounts broadcasted in plaintext (privacy issue)
- Address is long - takes lot of time to verify (user experience issue)
- Address prefix can be brute-forced, if too short or used to make
black hole address if longer (vandalism issue)

Commit protocol can be used for both the encryption and the
authentication while user experience is not bad and everything is
still secure.


 In case of RedPhone, you read those words verbally over not-yet-
 verified channel relying on difficulty of spoofing your voice. Also
 the app remembers the public keys, so you don't need to verify
 second time.

 This is reasonable, but wouldn't help in the case of an ad-hoc
 connection between parties who don't know each other well.

 I suggest you to try RedPhone (called Signal on iPhone) yourself.
 It's free/open source, Internet-based and end-to-end encrypted. You
 may find it useful some day. Also I'm willing to help you with
 trying it after I wake up. (~8 hours: Send me private e-mail if
 you want to.)

 I appreciate the offer. I really don't trust *any* smartphone as a
 platform for secure communication/data. But encrypting on the wire does
 of course shrink the attack surface and increase the attacker's cost.

 e

 Dňa 6. februára 2015 1:22:23 CET používateľ Eric Voskuil
 e...@voskuil.org napísal:

 On 02/05/2015 04:04 PM, MⒶrtin HⒶboⓋštiak wrote:
 That's exactly what I though when seeing the RedPhone code, but after
 I studied the commit protocol I realized it's actually secure and
 convenient way to do it. You should do that too. :)

 I was analyzing the model as you described it to me. A formal analysis
 of the security model of a particular implementation, based on
 inference
from source code, is a bit beyond what I signed up for. But I'm
 perfectly willing to comment on your description of the model if you
 are
 willing to indulge me.

 Shortly, how it works:
 The initiator of the connection sends commit message containing the
 hash of his temporary public ECDH part, second party sends back their
 public ECDH part and then initiator sends his public ECDH part in
 open. All three messages are hashed together and the first two bytes
 are used to select two words from a shared dictionary which are
 displayed on the screen of both the initiator and the second party.

 The parties communicate those two words and verify they match.

 How do they compare words if they haven't yet established a secure
 channel?

 If an attacker wants to do MITM, he has a chance of choosing right
 public parts 1:65536. There is no way to brute-force it, since that
 would be noticed immediately. If instead of two words based on the
 first two bytes, four words from BIP39 wordlist were chosen, it would
 provide entropy of 44 bits which I believe should be enough even for
 paranoid people.

 How this would work in Bitcoin payment scenario: user's phone
 broadcasts his name, merchant inputs amount and selects the name from
 the list, commit message is sent (and then the remaining two
 messages), merchant spells four words he sees on the screen and buyer
 confirms transaction after verifying that words match.

 So the assumption is that there exists a secure (as in proximity-based)
 communication channel?

 e

 2015-02-06 0:46 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can
 resolve the
 integrity issues, but because of the public nature of the
 broadcast
 coupled with strong public identity, the privacy compromise is
 much
 worse. Now transactions are cryptographically tainted.

 This is also the problem 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-06 Thread Eric Voskuil
On 02/06/2015 12:59 AM, Roy Badami wrote:
 In this case there is no need for P2P communication, just pay to an
 address you already have for the other party. If you want to avoid
 address reuse, use stealth addressing.

 But yes, if you don't have a stealth address for the other party you can
 certainly communicate in private as peers where you trust that you share
 a public key. The core issue here is really bootstrapping of that trust
 in an ad hoc manner.
 
 Something interactive might still be nicer, though, to avoid the risk
 of paying to an address that the payee no longer has the private key
 for.  Nooo!! Don't pay to that address.  I lost my old phone so I
 generated a new wallet.

Certainly, which brings us back to proximity.

Which reminds me - it's important to keep in mind the scenario that
arises when there is no person present to represent the receiver. Such
as a vending machine purchase.

Proximity in these cases is insufficient, as the receiver is not able to
prevent application of a fraudulent NFC device or replacement of a
static QR code. In these cases BIP-70 becomes essential.

e



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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Andreas Schildbach
Thanks Paul, for writing up your protocol!

First thoughts:

For a BIP standard, I think we should skip bitcoin: URIs entirely and
publish BIP70 payment requests instead. URIs mainly stick around because
of QR codes limited capacity. BIP70 would partly address the copycat
problem by signing payment requests.

In your Motivation section, I miss some words about NFC. NFC already
addresses all of the usability issues mentioned and is supported by
mobile wallets since 2011. That doesn't mean your method doesn't make
sense in some situations, but I think it should be explained why to
prefer broadcasting payment requests over picking them up via near field
radio.


On 02/05/2015 09:01 AM, Paul Puey wrote:
 Airbitz has developed and implemented a method for communicating a
 bitcoin URI across Bluetooth (BLE) or any other P2P, mid range,
 wireless, broadcast medium. The currently documented implementation is
 available in our iOS and Android mobile wallet (updated Android version
 with BLE coming in about 1 week). We would like to have the BIP pulled
 into Github for review and discussion. Here is the current BIP:
 
 
 BIP: TBD
 
 Title: P2P Wireless URI transfer
 
 Authors: Thomas Baker tom’at’airbitz.co http://airbitz.co, Paul Puey
 paul’at’airbitz.co http://airbitz.co
 
 Contributors: Joey Krug joeykrug’at’gmail.com http://gmail.com
 
 Status: proposal
 
 Type: Standards Track
 
 Created: 2015-01-12
 
 
 Table of Contents
 
   *
 
 Abstract
 
   *
 
 Motivation
 
   *
 
 Specification
 
   *
 
 Compatibility
 
   *
 
 Examples
 
   *
 
 References
 
 
 Abstract
 
 This is a protocol for peer-to-peer wireless transfer of a URI request
 using an open broadcast or advertisement channel such as Bluetooth,
 Bluetooth Low Energy, or WiFi Direct.
 
 
 Motivation
 
 There are disadvantages for a merchant (requester) and customer (sender)
 to exchange a URI request using QR codes that can be eliminated by using
 wireless broadcast or advertisements.
 
 Current QR code scan method to transfer a request URI from merchant
 (Requester) to customer (Sender) is cumbersome. A usual scenario is a
 merchant with a POS terminal for order entry and a separate tablet for
 transacting payments with bitcoin, and a customer with a smartphone.
 After the order is entered, the merchant enters payment request
 information into the tablet, generates the QR code representing the URI,
 and presents this to the customer. The customer prepares to scan the QR
 code with their smartphone by maneuvering the camera to the tablet. The
 tablet screen must be relatively clean, point at the customer, and held
 steady. The smartphone camera lens must be clean, point at the tablet
 screen, come into range, and held steady to focus and wait for a QR
 scan. Environmental conditions such as bright outdoor sunlight, indoor
 spot lights, or significant distance between QR code and camera can
 create difficult and cumbersome experiences for users.
 
 Using a wireless local broadcast allows the merchant to just enter the
 payment and wait. The tablet and smartphone are not maneuvered to align
 in any way. The customer observes broadcast listings, selects the
 appropriate one from possible simultaneous broadcasts from other POS
 stations nearby, examines the URI request details such as amount, and
 decides whether to send funds, initiating a bitcoin network transfer.
 The merchant and customer then receive the transaction confirmations and
 are done with the sale. Merchant and customer devices are kept private
 and secured in their own possession.
 
 The URI and other broadcast identification (Joe’s Grill #1) only contain
 public information. However, a copycat broadcaster acting as MITM might
 duplicate the broadcast simultaneously as the merchant, attempting to
 lure the customer to send funds to the copycat. That attack is mitigated
 with this broadcast method because of the partial address in the broadcast.
 
 
 Specification
 
 Requester generates a bitcoin URI request of variable length, and a
 limited descriptive identifier string. Requester then broadcasts the
 URI’s partial public address (paddress) plus identifier (id) over a
 publicly visible wireless channel.
 
 Sender scans for broadcasts on their device, examines and selects the
 desired request by the identifier and partial address. This connects a
 data channel to Requester.
 
 Requester sends full URI back over the data channel.
 
 Sender device ensures paddress is part of the full URI public address
 and checks the full address integrity. Checking the broadcast and full
 URI integrity prevents a copycat device within range from copying the
 partial address and fooling the customer into sending funds to the
 copycat instead.
 
 Below is a description of the protocol through Bluetooth Smart (Low Energy).
 
 Requestor  Sender - Bitcoin transaction roles
 
 Peripheral Central- Bluetooth GAP definitions
 
   Mode   Mode
 
 1   

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Mike Hearn

 For a BIP standard, I think we should skip bitcoin: URIs entirely and
 publish BIP70 payment requests instead.


Agreed - it's not clear to me at all that this partial address scheme is
actually secure. The assumption appears to be that the MITM must match the
address prefix generated by the genuine merchant. But if they can do a
wireless MITM they can just substitute their own address prefix/partial
address, no?

To avoid MITM attacks the sender must know who they are sending money to,
and that means they must see a human understandable name that's
cryptographically bound to the right public key. Displaying partial
addresses to the user is not going to solve this unless users manually
compare key prefixes across the screens which is even less convenient
than a QR code.

I think it should be explained why to
 prefer broadcasting payment requests over picking them up via near field
 radio.


This is probably an artifact of Apple's restrictions on iOS. Only the
iPhone 6 has NFC hardware and Apple don't expose it via any public API. It
can however support Bluetooth LE.

Apple isn't a big deal in Germany because iPhone only achieved about 17%
market share during the quarter when the iPhone 6 launched. Normally it's
closer to 10-13%. Most other markets are similar.

However in the USA, UK, Australia and Japan iOS is still a big deal and NFC
is going to be seen as a non-universal solution there. At least, until
Apple catches up and provides an NFC API.

It's certainly not a problem to have a working radio based broadcast
system, though the theoretician in me wonders what  happens when lots of
people are trying to pay simultaneously for something that has equal cost
. e.g. buying movie tickets at a counter. NFC and QR codes prevent any
kind of oops I paid for someone elses stuff confusion.

In practice of course Bitcoin payments are not normally popular enough for
this to be a problem outside of Bitcoin community events.
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
On 02/05/2015 12:28 PM, Mike Hearn wrote:
 The donation to live performer example is good - there's no issue of
 accidentally paying for someone else in this context as there's only one
 recipient, but many senders.

I'm not sure you could assume this, even if the payer only received one
broadcast. And if the payer receives multiple, it constitutes a DOS on
the scenario, potentially unintentional.

 The issue of confused payments remains in other situations though.

Agree, the problem of the payer strongly identifying the receiver
requires either proximity (NFC or QR code scan from the known-good
source) or PKI/WoT. The problem can't be resolved through a broadcast.

 For the coffee shop use case, it'd be nicer (I think) if we aim for a
 Square-style UI where the device broadcasts a (link to) a photo of the
 user combined with a bluetooth MAC. Then the merchant tablet can show
 faces of people in the shop, and can push a payment request to the users
 device. That device can then buzz the user, show a confirmation screen,
 put something on their smart watch etc or just auto-authorise the
 payment because the BIP70 signature is from a trusted merchant. User
 never even needs to touch their phone at all.

I'm imagining myself walking around broadcasting my photo and MAC
address while hucksters push payment requests to me for approval, while
recording my photo and correlating it to my address. It will pretty
quickly turn in to a scenario where I need to touch something before
this is turned on.

 On Thu, Feb 5, 2015 at 9:06 PM, Paul Puey p...@airbitz.co
 mailto:p...@airbitz.co wrote:
 
 The BIP70 protocol would preclude individuals from utilizing the P2P
 transfer spec. It would also require that a Sender have internet
 connectivity to get the payment protocol info. BLE could enable
 payment w/o internet by first transferring the URI to from Recipient
 to Sender. Then in the future, we could sign a Tx and send it over
 BLE back to the recipient (who would still need internet to verify
 the Tx). This is an important use case for areas with poor 3G/4G
 connectivity as I've experience myself.
 
 Also, due to Android issues, NFC is incredibly clunky. The URI
 Sender is required to tap the screen *while* the two phones are in
 contact. We support NFC the same way Bitcoin Wallet does, but unless
 the payment recipient has a custom Android device (which a merchant
 might) then the usage model is worse than scanning a QR code. BLE
 also allows people to pay at a distance such as for a donation to a
 live performer. We'll look at adding this to the Motivation section.
 
 From: Andreas Schildbach andreas@sc... - 2015-02-05 13:47:04
 
 Thanks Paul, for writing up your protocol!
 
 First thoughts:
 
 For a BIP standard, I think we should skip bitcoin: URIs entirely and
 publish BIP70 payment requests instead. URIs mainly stick around because
 of QR codes limited capacity. BIP70 would partly address the copycat
 problem by signing payment requests.
 
 In your Motivation section, I miss some words about NFC. NFC already
 addresses all of the usability issues mentioned and is supported by
 mobile wallets since 2011. That doesn't mean your method doesn't make
 sense in some situations, but I think it should be explained why to
 prefer broadcasting payment requests over picking them up via near field
 radio.




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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
Yes, a stellar device for mass surveillance coupled with transaction tainting.

e


 On Feb 5, 2015, at 1:19 PM, Brian Hoffman brianchoff...@gmail.com wrote:
 
 This sounds horrible. You could basically monitor anyone with a wallet in a 
 highly populated area and track them super easily by doing facial 
 recognition. Yes you could photograph people but it's way more burdensome. 
 Sorry to go off topic a little.
 
 
 On Feb 5, 2015, at 3:50 PM, Mike Hearn m...@plan99.net wrote:
 
 I'm imagining myself walking around broadcasting my photo and MAC
 address while hucksters push payment requests to me for approval
 
 I hate to break it to you, but you broadcast a photo of your face every time 
 you walk outside ;)
 
 Bluetooth MAC addresses are random, they aren't useful identifiers. If 
 someone can see you, a face is a far more uniquely identifying thing than a 
 MAC.
 
 Payment spam might be a problem. I can imagine a wallet requiring that 
 such requests are signed and then spammers can be blacklisted in the usual 
 fashion so they can't push things to your phone anymore. Anyway, a hurdle 
 that can be jumped if/when it becomes an issue.
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Mike Hearn

 This sounds horrible. You could basically monitor anyone with a wallet in
 a highly populated area and track them super easily by doing facial
 recognition.


We're talking about BLE, still? The radio tech that runs in the so called
junk bands because propagation is so poor?

My watch loses its connection to my phone if I just put it down and walk
around my apartment. I'm all for reasonable paranoia, but Bluetooth isn't
going to be enabling mass surveillance any time soon. It barely goes
through air, let alone walls.

Anyway, whatever. I'm just bouncing around ideas for faster user
interfaces. You could always switch it off or set it to be triggered by the
presence of particular wifi hotspots, if you don't mind an initial bit of
setup.

Back on topic - the debate is interesting, but I think to get this to the
stage of being a BIP we'd need at least another wallet to implement it?
Then I guess a BIP would be useful regardless of the design issues. The
prefix matching still feels flaky to me but it's hard to know if you could
really swipe payments out of the air in practice, without actually trying
it.
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Mike Hearn

 I'm imagining myself walking around broadcasting my photo and MAC
 address while hucksters push payment requests to me for approval


I hate to break it to you, but you broadcast a photo of your face every
time you walk outside ;)

Bluetooth MAC addresses are random, they aren't useful identifiers. If
someone can see you, a face is a far more uniquely identifying thing than a
MAC.

Payment spam might be a problem. I can imagine a wallet requiring that
such requests are signed and then spammers can be blacklisted in the usual
fashion so they can't push things to your phone anymore. Anyway, a hurdle
that can be jumped if/when it becomes an issue.
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
On 02/05/2015 12:50 PM, Mike Hearn wrote:
 I'm imagining myself walking around broadcasting my photo and MAC
 address while hucksters push payment requests to me for approval
 
 I hate to break it to you, but you broadcast a photo of your face every
 time you walk outside ;)
 
 Bluetooth MAC addresses are random, they aren't useful identifiers. If
 someone can see you, a face is a far more uniquely identifying thing
 than a MAC.

Interesting take on privacy. But the market will of course decide.

Would the merchant be broadcasting payment requests in the clear, or
would they be encrypted with a public key of the spender?

 Payment spam might be a problem. I can imagine a wallet requiring that
 such requests are signed and then spammers can be blacklisted in the
 usual fashion so they can't push things to your phone anymore. Anyway, a
 hurdle that can be jumped if/when it becomes an issue.

Not sure I'd shoot for a system that's guaranteed to require PKI with
blacklisting and spam filtering.

e



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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
BLE has an advertised range of over 100m. 

http://www.bluetooth.com/Pages/low-energy-tech-info.aspx

In the case of mass surveillance that range could most likely be extended 
dramatically by the reviewer. I've seen  WiFi ranges of over a mile with a 
strong (not FCC approved) receiver.

WiFi hotspots don't have strong identity or a guaranteed position, so they 
can't be trusted for location.

e

On Feb 5, 2015, at 1:36 PM, Mike Hearn m...@plan99.net wrote:

 This sounds horrible. You could basically monitor anyone with a wallet in a 
 highly populated area and track them super easily by doing facial 
 recognition.
 
 We're talking about BLE, still? The radio tech that runs in the so called 
 junk bands because propagation is so poor?
 
 My watch loses its connection to my phone if I just put it down and walk 
 around my apartment. I'm all for reasonable paranoia, but Bluetooth isn't 
 going to be enabling mass surveillance any time soon. It barely goes through 
 air, let alone walls.
 
 Anyway, whatever. I'm just bouncing around ideas for faster user interfaces. 
 You could always switch it off or set it to be triggered by the presence of 
 particular wifi hotspots, if you don't mind an initial bit of setup.
 
 Back on topic - the debate is interesting, but I think to get this to the 
 stage of being a BIP we'd need at least another wallet to implement it? Then 
 I guess a BIP would be useful regardless of the design issues. The prefix 
 matching still feels flaky to me but it's hard to know if you could really 
 swipe payments out of the air in practice, without actually trying it.
 
 
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[Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
Airbitz has developed and implemented a method for communicating a bitcoin
URI across Bluetooth (BLE) or any other P2P, mid range, wireless, broadcast
medium. The currently documented implementation is available in our iOS and
Android mobile wallet (updated Android version with BLE coming in about 1
week). We would like to have the BIP pulled into Github for review and
discussion. Here is the current BIP:


BIP: TBD

Title: P2P Wireless URI transfer

Authors: Thomas Baker tom’at’airbitz.co, Paul Puey paul’at’airbitz.co

Contributors: Joey Krug joeykrug’at’gmail.com

Status: proposal

Type: Standards Track

Created: 2015-01-12

Table of Contents

   -

   Abstract
   -

   Motivation
   -

   Specification
   -

   Compatibility
   -

   Examples
   -

   References

Abstract

This is a protocol for peer-to-peer wireless transfer of a URI request
using an open broadcast or advertisement channel such as Bluetooth,
Bluetooth Low Energy, or WiFi Direct.
Motivation

There are disadvantages for a merchant (requester) and customer (sender) to
exchange a URI request using QR codes that can be eliminated by using
wireless broadcast or advertisements.

Current QR code scan method to transfer a request URI from merchant
(Requester) to customer (Sender) is cumbersome. A usual scenario is a
merchant with a POS terminal for order entry and a separate tablet for
transacting payments with bitcoin, and a customer with a smartphone. After
the order is entered, the merchant enters payment request information into
the tablet, generates the QR code representing the URI, and presents this
to the customer. The customer prepares to scan the QR code with their
smartphone by maneuvering the camera to the tablet. The tablet screen must
be relatively clean, point at the customer, and held steady. The smartphone
camera lens must be clean, point at the tablet screen, come into range, and
held steady to focus and wait for a QR scan. Environmental conditions such
as bright outdoor sunlight, indoor spot lights, or significant distance
between QR code and camera can create difficult and cumbersome experiences
for users.

Using a wireless local broadcast allows the merchant to just enter the
payment and wait. The tablet and smartphone are not maneuvered to align in
any way. The customer observes broadcast listings, selects the appropriate
one from possible simultaneous broadcasts from other POS stations nearby,
examines the URI request details such as amount, and decides whether to
send funds, initiating a bitcoin network transfer. The merchant and
customer then receive the transaction confirmations and are done with the
sale. Merchant and customer devices are kept private and secured in their
own possession.

The URI and other broadcast identification (Joe’s Grill #1) only contain
public information. However, a copycat broadcaster acting as MITM might
duplicate the broadcast simultaneously as the merchant, attempting to lure
the customer to send funds to the copycat. That attack is mitigated with
this broadcast method because of the partial address in the broadcast.
Specification

Requester generates a bitcoin URI request of variable length, and a limited
descriptive identifier string. Requester then broadcasts the URI’s partial
public address (paddress) plus identifier (id) over a publicly visible
wireless channel.

Sender scans for broadcasts on their device, examines and selects the
desired request by the identifier and partial address. This connects a data
channel to Requester.

Requester sends full URI back over the data channel.

Sender device ensures paddress is part of the full URI public address and
checks the full address integrity. Checking the broadcast and full URI
integrity prevents a copycat device within range from copying the partial
address and fooling the customer into sending funds to the copycat instead.

Below is a description of the protocol through Bluetooth Smart (Low Energy).

Requestor  Sender - Bitcoin transaction roles

Peripheral Central- Bluetooth GAP definitions

  Mode   Mode

1   |-|   - Requestor Advertises partial bitcoin: URI +
Name

   | ...  |

2   |-|   - Subscribe then send sender's Name, requesting
a response

3   |-|   - ACK

4   |-|   - request Read Characteristic from peripheral

5   |-|   - Sender receives full bitcoin: URI


   1.

   Peripheral advertises over a service UUID a BLE extended advertisement
   with a Scan Response containing the partial address of a bitcoin URI and a
   Name, any plain text. The entire response is limited to 26 characters. The
   first 10 make up the first 10 characters of the bitcoin URI public address
   where to send bitcoin, and must be present. The remaining characters are
   any plain text such as “The Habit 1” or “Starbucks-Reg 1”, more human
   readable information. The partial address serves as a check against a
   nearby attacker who may try 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
Hi Paul,

The issue is in the establishment of trust. Anyone can broadcast the initial 
information.

e

 On Feb 5, 2015, at 2:01 PM, Paul Puey p...@airbitz.co wrote:
 
 The broadcast is ONLY done when the wallet is in Receive mode. Same as when 
 the QR code is visible. The use of the *Name* section is specifically so that 
 a recipient can broadcast their name/handle. Not so the recipient would 
 broadcast the name of the Sender.
 
 On Thu, Feb 5, 2015 at 12:50 PM, Mike Hearn m...@plan99.net wrote:
 I'm imagining myself walking around broadcasting my photo and MAC
 address while hucksters push payment requests to me for approval
 
 I hate to break it to you, but you broadcast a photo of your face every time 
 you walk outside ;)
 
 Bluetooth MAC addresses are random, they aren't useful identifiers. If 
 someone can see you, a face is a far more uniquely identifying thing than a 
 MAC.
 
 Payment spam might be a problem. I can imagine a wallet requiring that 
 such requests are signed and then spammers can be blacklisted in the usual 
 fashion so they can't push things to your phone anymore. Anyway, a hurdle 
 that can be jumped if/when it becomes an issue.
 
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
So if you picked up the BLE broadcast request. All you know is that
*someone* within 100m is requesting bitcoin at a certain address. Not
necessarily who. The *name* is both optional, and possibly just a *handle*
of the user. If I'm sitting 5 ft away from someone at dinner and wanted to
pay them via BLE, I might see Monkey Dude on my list and simply ask him
is that you? If so, I send it. If there are two Monkey Dude's Then I
have to bother with the address prefix, but not otherwise.


[image: logo]
*Paul Puey* CEO / Co-Founder, Airbitz Inc
+1-619-850-8624 | http://airbitz.co | San Diego
http://facebook.com/airbitz  http://twitter.com/airbitz
https://plus.google.com/118173667510609425617
https://go.airbitz.co/comments/feed/  http://linkedin.com/in/paulpuey
https://angel.co/paul-puey
*DOWNLOAD THE AIRBITZ WALLET:*
  https://play.google.com/store/apps/details?id=com.airbitz
https://itunes.apple.com/us/app/airbitz/id843536046




On Thu, Feb 5, 2015 at 1:46 PM, Eric Voskuil e...@voskuil.org wrote:

 BLE has an advertised range of over 100m.

 http://www.bluetooth.com/Pages/low-energy-tech-info.aspx

 In the case of mass surveillance that range could most likely be extended
 dramatically by the reviewer. I've seen  WiFi ranges of over a mile with a
 strong (not FCC approved) receiver.

 WiFi hotspots don't have strong identity or a guaranteed position, so they
 can't be trusted for location.

 e

 On Feb 5, 2015, at 1:36 PM, Mike Hearn m...@plan99.net wrote:

 This sounds horrible. You could basically monitor anyone with a wallet in
 a highly populated area and track them super easily by doing facial
 recognition.


 We're talking about BLE, still? The radio tech that runs in the so called
 junk bands because propagation is so poor?

 My watch loses its connection to my phone if I just put it down and walk
 around my apartment. I'm all for reasonable paranoia, but Bluetooth isn't
 going to be enabling mass surveillance any time soon. It barely goes
 through air, let alone walls.

 Anyway, whatever. I'm just bouncing around ideas for faster user
 interfaces. You could always switch it off or set it to be triggered by the
 presence of particular wifi hotspots, if you don't mind an initial bit of
 setup.

 Back on topic - the debate is interesting, but I think to get this to the
 stage of being a BIP we'd need at least another wallet to implement it?
 Then I guess a BIP would be useful regardless of the design issues. The
 prefix matching still feels flaky to me but it's hard to know if you could
 really swipe payments out of the air in practice, without actually trying
 it.



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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
A MITM can receive the initial broadcast and then spoof it by jamming the 
original. You then only see one.

e

 On Feb 5, 2015, at 2:07 PM, Paul Puey p...@airbitz.co wrote:
 
 So if you picked up the BLE broadcast request. All you know is that *someone* 
 within 100m is requesting bitcoin at a certain address. Not necessarily who. 
 The *name* is both optional, and possibly just a *handle* of the user. If I'm 
 sitting 5 ft away from someone at dinner and wanted to pay them via BLE, I 
 might see Monkey Dude on my list and simply ask him is that you? If so, I 
 send it. If there are two Monkey Dude's Then I have to bother with the 
 address prefix, but not otherwise.
 
 On Thu, Feb 5, 2015 at 1:46 PM, Eric Voskuil e...@voskuil.org wrote:
 BLE has an advertised range of over 100m. 
 
 http://www.bluetooth.com/Pages/low-energy-tech-info.aspx
 
 In the case of mass surveillance that range could most likely be extended 
 dramatically by the reviewer. I've seen  WiFi ranges of over a mile with a 
 strong (not FCC approved) receiver.
 
 WiFi hotspots don't have strong identity or a guaranteed position, so they 
 can't be trusted for location.
 
 e
 
 On Feb 5, 2015, at 1:36 PM, Mike Hearn m...@plan99.net wrote:
 
 This sounds horrible. You could basically monitor anyone with a wallet in 
 a highly populated area and track them super easily by doing facial 
 recognition.
 
 We're talking about BLE, still? The radio tech that runs in the so called 
 junk bands because propagation is so poor?
 
 My watch loses its connection to my phone if I just put it down and walk 
 around my apartment. I'm all for reasonable paranoia, but Bluetooth isn't 
 going to be enabling mass surveillance any time soon. It barely goes 
 through air, let alone walls.
 
 Anyway, whatever. I'm just bouncing around ideas for faster user 
 interfaces. You could always switch it off or set it to be triggered by the 
 presence of particular wifi hotspots, if you don't mind an initial bit of 
 setup.
 
 Back on topic - the debate is interesting, but I think to get this to the 
 stage of being a BIP we'd need at least another wallet to implement it? 
 Then I guess a BIP would be useful regardless of the design issues. The 
 prefix matching still feels flaky to me but it's hard to know if you could 
 really swipe payments out of the air in practice, without actually trying 
 it.
 
--
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
The broadcast is ONLY done when the wallet is in Receive mode. Same as when
the QR code is visible. The use of the *Name* section is specifically so
that a recipient can broadcast their name/handle. Not so the recipient
would broadcast the name of the Sender.


[image: logo]
*Paul Puey* CEO / Co-Founder, Airbitz Inc
+1-619-850-8624 | http://airbitz.co | San Diego
http://facebook.com/airbitz  http://twitter.com/airbitz
https://plus.google.com/118173667510609425617
https://go.airbitz.co/comments/feed/  http://linkedin.com/in/paulpuey
https://angel.co/paul-puey
*DOWNLOAD THE AIRBITZ WALLET:*
  https://play.google.com/store/apps/details?id=com.airbitz
https://itunes.apple.com/us/app/airbitz/id843536046




On Thu, Feb 5, 2015 at 12:50 PM, Mike Hearn m...@plan99.net wrote:

 I'm imagining myself walking around broadcasting my photo and MAC
 address while hucksters push payment requests to me for approval


 I hate to break it to you, but you broadcast a photo of your face every
 time you walk outside ;)

 Bluetooth MAC addresses are random, they aren't useful identifiers. If
 someone can see you, a face is a far more uniquely identifying thing than a
 MAC.

 Payment spam might be a problem. I can imagine a wallet requiring that
 such requests are signed and then spammers can be blacklisted in the usual
 fashion so they can't push things to your phone anymore. Anyway, a hurdle
 that can be jumped if/when it becomes an issue.

--
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sponsored by Intel and developed in partnership with Slashdot Media, is your
hub for all things parallel software development, from weekly thought
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
The implementation on Airbitz does not encourage or even let a user
broadcast a photo. Just an address prefix and name/handle. And it's only
broadcast during the Receive request. Not generally while the app is
running although that's up to the implementation.


[image: logo]
*Paul Puey* CEO / Co-Founder, Airbitz Inc
+1-619-850-8624 | http://airbitz.co | San Diego
http://facebook.com/airbitz  http://twitter.com/airbitz
https://plus.google.com/118173667510609425617
https://go.airbitz.co/comments/feed/  http://linkedin.com/in/paulpuey
https://angel.co/paul-puey
*DOWNLOAD THE AIRBITZ WALLET:*
  https://play.google.com/store/apps/details?id=com.airbitz
https://itunes.apple.com/us/app/airbitz/id843536046




On Thu, Feb 5, 2015 at 1:19 PM, Brian Hoffman brianchoff...@gmail.com
wrote:

 This sounds horrible. You could basically monitor anyone with a wallet in
 a highly populated area and track them super easily by doing facial
 recognition. Yes you could photograph people but it's way more burdensome.
 Sorry to go off topic a little.


 On Feb 5, 2015, at 3:50 PM, Mike Hearn m...@plan99.net wrote:

 I'm imagining myself walking around broadcasting my photo and MAC
 address while hucksters push payment requests to me for approval


 I hate to break it to you, but you broadcast a photo of your face every
 time you walk outside ;)

 Bluetooth MAC addresses are random, they aren't useful identifiers. If
 someone can see you, a face is a far more uniquely identifying thing than a
 MAC.

 Payment spam might be a problem. I can imagine a wallet requiring that
 such requests are signed and then spammers can be blacklisted in the usual
 fashion so they can't push things to your phone anymore. Anyway, a hurdle
 that can be jumped if/when it becomes an issue.


 --
 Dive into the World of Parallel Programming. The Go Parallel Website,
 sponsored by Intel and developed in partnership with Slashdot Media, is
 your
 hub for all things parallel software development, from weekly thought
 leadership blogs to news, videos, case studies, tutorials and more. Take a
 look and join the conversation now. http://goparallel.sourceforge.net/

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
Although not perfect, and it may require visual/verbal verification, I
don't see what the trust issue is.


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On Thu, Feb 5, 2015 at 2:05 PM, Eric Voskuil e...@voskuil.org wrote:

 Hi Paul,

 The issue is in the establishment of trust. Anyone can broadcast the
 initial information.

 e

 On Feb 5, 2015, at 2:01 PM, Paul Puey p...@airbitz.co wrote:

 The broadcast is ONLY done when the wallet is in Receive mode. Same as
 when the QR code is visible. The use of the *Name* section is specifically
 so that a recipient can broadcast their name/handle. Not so the recipient
 would broadcast the name of the Sender.

 On Thu, Feb 5, 2015 at 12:50 PM, Mike Hearn m...@plan99.net wrote:

 I'm imagining myself walking around broadcasting my photo and MAC
 address while hucksters push payment requests to me for approval


 I hate to break it to you, but you broadcast a photo of your face every
 time you walk outside ;)

 Bluetooth MAC addresses are random, they aren't useful identifiers. If
 someone can see you, a face is a far more uniquely identifying thing than a
 MAC.

 Payment spam might be a problem. I can imagine a wallet requiring that
 such requests are signed and then spammers can be blacklisted in the usual
 fashion so they can't push things to your phone anymore. Anyway, a hurdle
 that can be jumped if/when it becomes an issue.



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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Roy Badami
Personally I like the simplicity of tapping two phones together to
make payment - it should be quicker and easier than scanning QR codes
and it's a trust model that's hard to misunderstand.

Is NFC good enough for that?  I fear even with NFC it is possible to
produce a device with longer range than one would expect.  What
happened to the idea of tapping two devices together and then
comparing the timing of the tap (as detected by the phones'
accelerometers) to make spoofing a transaction harder?  I remember
hearing about that years ago - is that still a thing?

roy

On Thu, Feb 05, 2015 at 02:10:51PM -0800, Eric Voskuil wrote:
 A MITM can receive the initial broadcast and then spoof it by jamming the 
 original. You then only see one.
 
 e
 
  On Feb 5, 2015, at 2:07 PM, Paul Puey p...@airbitz.co wrote:
  
  So if you picked up the BLE broadcast request. All you know is that 
  *someone* within 100m is requesting bitcoin at a certain address. Not 
  necessarily who. The *name* is both optional, and possibly just a *handle* 
  of the user. If I'm sitting 5 ft away from someone at dinner and wanted to 
  pay them via BLE, I might see Monkey Dude on my list and simply ask him 
  is that you? If so, I send it. If there are two Monkey Dude's Then I 
  have to bother with the address prefix, but not otherwise.
  
  On Thu, Feb 5, 2015 at 1:46 PM, Eric Voskuil e...@voskuil.org wrote:
  BLE has an advertised range of over 100m. 
  
  http://www.bluetooth.com/Pages/low-energy-tech-info.aspx
  
  In the case of mass surveillance that range could most likely be extended 
  dramatically by the reviewer. I've seen  WiFi ranges of over a mile with a 
  strong (not FCC approved) receiver.
  
  WiFi hotspots don't have strong identity or a guaranteed position, so they 
  can't be trusted for location.
  
  e
  
  On Feb 5, 2015, at 1:36 PM, Mike Hearn m...@plan99.net wrote:
  
  This sounds horrible. You could basically monitor anyone with a wallet 
  in a highly populated area and track them super easily by doing facial 
  recognition.
  
  We're talking about BLE, still? The radio tech that runs in the so called 
  junk bands because propagation is so poor?
  
  My watch loses its connection to my phone if I just put it down and walk 
  around my apartment. I'm all for reasonable paranoia, but Bluetooth isn't 
  going to be enabling mass surveillance any time soon. It barely goes 
  through air, let alone walls.
  
  Anyway, whatever. I'm just bouncing around ideas for faster user 
  interfaces. You could always switch it off or set it to be triggered by 
  the presence of particular wifi hotspots, if you don't mind an initial 
  bit of setup.
  
  Back on topic - the debate is interesting, but I think to get this to the 
  stage of being a BIP we'd need at least another wallet to implement it? 
  Then I guess a BIP would be useful regardless of the design issues. The 
  prefix matching still feels flaky to me but it's hard to know if you 
  could really swipe payments out of the air in practice, without actually 
  trying it.
  

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread William Swanson
On Thu, Feb 5, 2015 at 2:10 PM, Eric Voskuil e...@voskuil.org wrote:
 A MITM can receive the initial broadcast and then spoof it by jamming the
 original. You then only see one.

You are right, of course. There is no way to make Bluetooth 100%
secure, since it is an over-the-air technology. You could try securing
it using a CA or other identity server, but now you've excluded ad-hoc
person-to-person payments. Plus, you need an active internet
connection to reach the CA.

You can try using proximity as a substitute for identity, like
requiring NFC to kick-start the connection, but at that point you
might as well use QR codes.

This BIP is not trying to provide absolute bullet-proof security,
since that's impossible given the physical limitations of the
Bluetooth technology. Instead, it's trying to provide the
best-possible security given those constraints. In exchange for this,
we get greatly enhanced usability in common scenarios.

There are plenty of usable, real-world technologies with big security
holes. Anybody with lock-picking experience will tell you this, but
nobody is welding their front door shut. The ability to go in and out
is worth the security risk.

Bluetooth payments add a whole new dimension to real-world Bitcoin
usability. Do we shut that down because it can't be made perfect, or
do we do the best we can and move forward?

-William

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
On 02/05/2015 02:08 PM, Paul Puey wrote:
 Although not perfect, and it may require visual/verbal verification,
 I don't see what the trust issue is.

I agree that with manual verification between the parties the worst
problem becomes DOS, which is certainly not catastrophic.

But the objective is to the extent possible improve upon the cumbersome
process of QR code, NFC signal, or textual address scanning. Given that
there would be no way to know you are under attack, with the exception
of manual confirmation, it would seem unwise to ever rely on the
automation. If the automation cannot be relied upon, it may actually
make matters worse. People would either take their chances by relying on
it or go through a more complex process.

In terms of the difficulty of an attack, it's important to recognize
that all attacks (DOS, privacy, integrity) in this scenario can be
fully-automated and executed over the air by a black box at some distance:

* DOS is possible by rebroadcasting a similar request.

* Privacy is compromised by monitoring for payment requests and
correlating them to location and potentially images of parties.

* Integrity is compromised by either:
(1) Rebroadcasting a similar transaction with a bogus address but with
the same leading characters; can't be spent but you lose your money.
(2) Rebroadcasting with a valid address that doesn't match the leading
characters, in the expectation that the user doesn't check manually.

Regarding possible mitigation via BIP-70:

A BIP-70 signed payment request in the initial broadcast can resolve the
integrity issues, but because of the public nature of the broadcast
coupled with strong public identity, the privacy compromise is much
worse. Now transactions are cryptographically tainted.

This is also the problem with BIP-70 over the web. TLS and other
security precautions aside, an interloper on the communication, desktop,
datacenter, etc., can capture payment requests and strongly correlate
transactions to identities in an automated manner. The payment request
must be kept private between the parties, and that's hard to do.

So the initial broadcast needs privacy, but then of course it cannot be
a broadcast - it need to be a narrow cast. That brings us back to
proximity-based establishment.

I think that you could get away with this for a while, simply because of
the narrow fields we are working in presently. But in a bitcoin world it
would be very problematic. For this reason I wouldn't want to encourage
standardization on this approach.

e

On 02/05/2015 02:10 PM, Eric Voskuil wrote:
 A MITM can receive the initial broadcast and then spoof it by jamming
 the original. You then only see one.
 
 e
 
 On Feb 5, 2015, at 2:07 PM, Paul Puey p...@airbitz.co
 mailto:p...@airbitz.co wrote:
 
 So if you picked up the BLE broadcast request. All you know is that
 *someone* within 100m is requesting bitcoin at a certain address. Not
 necessarily who. The *name* is both optional, and possibly just a
 *handle* of the user. If I'm sitting 5 ft away from someone at dinner
 and wanted to pay them via BLE, I might see Monkey Dude on my list
 and simply ask him is that you? If so, I send it. If there are two
 Monkey Dude's Then I have to bother with the address prefix, but not
 otherwise.

 On Thu, Feb 5, 2015 at 1:46 PM, Eric Voskuil e...@voskuil.org
 mailto:e...@voskuil.org wrote:

 BLE has an advertised range of over 100m. 

 http://www.bluetooth.com/Pages/low-energy-tech-info.aspx

 In the case of mass surveillance that range could most likely be
 extended dramatically by the reviewer. I've seen  WiFi ranges of
 over a mile with a strong (not FCC approved) receiver.

 WiFi hotspots don't have strong identity or a guaranteed position,
 so they can't be trusted for location.

 e

 On Feb 5, 2015, at 1:36 PM, Mike Hearn m...@plan99.net
 mailto:m...@plan99.net wrote:

 This sounds horrible. You could basically monitor anyone with
 a wallet in a highly populated area and track them super
 easily by doing facial recognition.


 We're talking about BLE, still? The radio tech that runs in the
 so called junk bands because propagation is so poor?

 My watch loses its connection to my phone if I just put it down
 and walk around my apartment. I'm all for reasonable paranoia,
 but Bluetooth isn't going to be enabling mass surveillance any
 time soon. It barely goes through air, let alone walls.

 Anyway, whatever. I'm just bouncing around ideas for faster user
 interfaces. You could always switch it off or set it to be
 triggered by the presence of particular wifi hotspots, if you
 don't mind an initial bit of setup.

 Back on topic - the debate is interesting, but I think to get
 this to the stage of being a BIP we'd need at least another
 wallet to implement it? Then I guess a BIP would be useful
 regardless of the design issues. The prefix matching still feels

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread MⒶrtin HⒶboⓋštiak
I would like to shortly express my opinion:

- Having BT as an alternative is good idea but it must be secure enough
- Signed BIP70 should be enough. I see only two issues regarding BIP70
(but they apply also to TCP/IP, not just BT): key revocations and MITM
attacks by governments.
- Broadcasting faces is very bad idea IMHO.
- Comparing addresses seems complicated but if hash was displayed as a
unique, picture hard to be mistake or long phrase, it could be more
convenient.
- Maybe storing public key (I do NOT mean bitcoin address!) of
merchant after successful transaction is good compromise?

Another idea: I noticed it's extremely easy to compare two strings if
they are the same size (in terms of millimeters, not number of
characters). If the hash of signing key was printed on a sign near the
POS in specified size (90% of smallest available screen?) and phone
would scale correctly, just putting the phone near the sign would be
enough to instantly spot whether the hashes are same.

Maybe instead of hex/base58 hash encoding use colored barcode. But I'm
not sure if it would improve things.

2015-02-05 23:49 GMT+01:00 Roy Badami r...@gnomon.org.uk:
 Personally I like the simplicity of tapping two phones together to
 make payment - it should be quicker and easier than scanning QR codes
 and it's a trust model that's hard to misunderstand.

 Is NFC good enough for that?  I fear even with NFC it is possible to
 produce a device with longer range than one would expect.  What
 happened to the idea of tapping two devices together and then
 comparing the timing of the tap (as detected by the phones'
 accelerometers) to make spoofing a transaction harder?  I remember
 hearing about that years ago - is that still a thing?

 roy

 On Thu, Feb 05, 2015 at 02:10:51PM -0800, Eric Voskuil wrote:
 A MITM can receive the initial broadcast and then spoof it by jamming the 
 original. You then only see one.

 e

  On Feb 5, 2015, at 2:07 PM, Paul Puey p...@airbitz.co wrote:
 
  So if you picked up the BLE broadcast request. All you know is that 
  *someone* within 100m is requesting bitcoin at a certain address. Not 
  necessarily who. The *name* is both optional, and possibly just a *handle* 
  of the user. If I'm sitting 5 ft away from someone at dinner and wanted to 
  pay them via BLE, I might see Monkey Dude on my list and simply ask him 
  is that you? If so, I send it. If there are two Monkey Dude's Then I 
  have to bother with the address prefix, but not otherwise.
 
  On Thu, Feb 5, 2015 at 1:46 PM, Eric Voskuil e...@voskuil.org wrote:
  BLE has an advertised range of over 100m.
 
  http://www.bluetooth.com/Pages/low-energy-tech-info.aspx
 
  In the case of mass surveillance that range could most likely be extended 
  dramatically by the reviewer. I've seen  WiFi ranges of over a mile with 
  a strong (not FCC approved) receiver.
 
  WiFi hotspots don't have strong identity or a guaranteed position, so 
  they can't be trusted for location.
 
  e
 
  On Feb 5, 2015, at 1:36 PM, Mike Hearn m...@plan99.net wrote:
 
  This sounds horrible. You could basically monitor anyone with a wallet 
  in a highly populated area and track them super easily by doing facial 
  recognition.
 
  We're talking about BLE, still? The radio tech that runs in the so 
  called junk bands because propagation is so poor?
 
  My watch loses its connection to my phone if I just put it down and walk 
  around my apartment. I'm all for reasonable paranoia, but Bluetooth 
  isn't going to be enabling mass surveillance any time soon. It barely 
  goes through air, let alone walls.
 
  Anyway, whatever. I'm just bouncing around ideas for faster user 
  interfaces. You could always switch it off or set it to be triggered by 
  the presence of particular wifi hotspots, if you don't mind an initial 
  bit of setup.
 
  Back on topic - the debate is interesting, but I think to get this to 
  the stage of being a BIP we'd need at least another wallet to implement 
  it? Then I guess a BIP would be useful regardless of the design issues. 
  The prefix matching still feels flaky to me but it's hard to know if you 
  could really swipe payments out of the air in practice, without actually 
  trying it.
 

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread MⒶrtin HⒶboⓋštiak
 A BIP-70 signed payment request in the initial broadcast can resolve the
 integrity issues, but because of the public nature of the broadcast
 coupled with strong public identity, the privacy compromise is much
 worse. Now transactions are cryptographically tainted.

 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication, desktop,
 datacenter, etc., can capture payment requests and strongly correlate
 transactions to identities in an automated manner. The payment request
 must be kept private between the parties, and that's hard to do.

What about using encryption with forward secrecy? Merchant would
generate signed request containing public ECDH part, buyer would send
back transaction encrypted with ECDH and his public ECDH part. If
receiving address/amount is meant to be private, use commit protocol
(see ZRTP/RedPhone) and short authentication phrase (which is hard to
spoof thanks to commit protocol - see RedPhone)?

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can resolve the
 integrity issues, but because of the public nature of the broadcast
 coupled with strong public identity, the privacy compromise is much
 worse. Now transactions are cryptographically tainted.

 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication, desktop,
 datacenter, etc., can capture payment requests and strongly correlate
 transactions to identities in an automated manner. The payment request
 must be kept private between the parties, and that's hard to do.
 
 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard to
 spoof thanks to commit protocol - see RedPhone)?

Hi Martin,

The problem is that you need to verify the ownership of the public key.
A MITM can substitute the key. If you don't have verifiable identity
associated with the public key (PKI/WoT), you need a shared secret (such
as a secret phrase). But the problem is then establishing that secret
over a public channel.

You can bootstrap a private session over the untrusted network using a
trusted public key (PKI/WoT). But the presumption is that you are
already doing this over the web (using TLS). That process is subject to
attack at the CA. WoT is not subject to a CA attack, because it's
decentralized. But it's also not sufficiently deployed for some scenarios.

e



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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
On 02/05/2015 03:34 PM, Roy Badami wrote:
 For peer-to-peer payments, how common do we think that the payment is
 of an ad hoc nature rather than to a known contact?
 
 If I want to pay my friends/colleagues/etc over a restaurant table
 there's no reason why I couldn't already have their public keys in my
 contact list - then it would be pretty straightforward to have a
 watertight mechanism where I would know who I was paying.  You could
 probably even relatively securely bootstrap a key exchange over SMS,
 relying only on the contacts already having each other in their
 phonebooks.

In this case there is no need for P2P communication, just pay to an
address you already have for the other party. If you want to avoid
address reuse, use stealth addressing.

But yes, if you don't have a stealth address for the other party you can
certainly communicate in private as peers where you trust that you share
a public key. The core issue here is really bootstrapping of that trust
in an ad hoc manner.

 As for comsumer-to-merchant transactions where the merchant is a
 bricks and mortar merchant, IMHO it absolutely has to be pay that
 terminal over there.  It's the trust model we all currently use -
 whether paying cash or card - and it's the only trust model that works
 IMHO (and customers and businesses alike are well aware of the risks
 of a fraudster standing behind the counter pretending to be an
 employee accepting payment - and by and large are pretty good at
 mitigating it).  OTOH as we've discussed here before there are many
 use cases where the custoemr doesn't actually know or care about the
 name of the shop or bar they walked into but is pretty damn sure that
 they need to make payment to the person over there behind the counter.

Yes, proximity is practically the universal solution to the problem of
the payer identifying the correct seller in any face-to-face scenario.

 Granted, there are cases taht dont' fall into either of the above -
 but they're the cases that are (a) harder to figure out how to
 authenticate and consequently (b) the use cases that are going to be
 most subject to attempted fraud.

When identification is required (show me some id before I pay you) it
equates to the BIP-70 scenario in the bitcoin model. This is also
required in order guard against repudiation (give me a signed receipt).

 On Thu, Feb 05, 2015 at 03:02:56PM -0800, William Swanson wrote:
 On Thu, Feb 5, 2015 at 2:10 PM, Eric Voskuil e...@voskuil.org wrote:
 A MITM can receive the initial broadcast and then spoof it by jamming the
 original. You then only see one.

 You are right, of course. There is no way to make Bluetooth 100%
 secure, since it is an over-the-air technology. You could try securing
 it using a CA or other identity server, but now you've excluded ad-hoc
 person-to-person payments. Plus, you need an active internet
 connection to reach the CA.

 You can try using proximity as a substitute for identity, like
 requiring NFC to kick-start the connection, but at that point you
 might as well use QR codes.

 This BIP is not trying to provide absolute bullet-proof security,
 since that's impossible given the physical limitations of the
 Bluetooth technology. Instead, it's trying to provide the
 best-possible security given those constraints. In exchange for this,
 we get greatly enhanced usability in common scenarios.

 There are plenty of usable, real-world technologies with big security
 holes. Anybody with lock-picking experience will tell you this, but
 nobody is welding their front door shut. The ability to go in and out
 is worth the security risk.

 Bluetooth payments add a whole new dimension to real-world Bitcoin
 usability. Do we shut that down because it can't be made perfect, or
 do we do the best we can and move forward?

 -William

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil

On 02/05/2015 04:04 PM, MⒶrtin HⒶboⓋštiak wrote:
 That's exactly what I though when seeing the RedPhone code, but after
 I studied the commit protocol I realized it's actually secure and
 convenient way to do it. You should do that too. :)

I was analyzing the model as you described it to me. A formal analysis
of the security model of a particular implementation, based on inference
from source code, is a bit beyond what I signed up for. But I'm
perfectly willing to comment on your description of the model if you are
willing to indulge me.

 Shortly, how it works:
 The initiator of the connection sends commit message containing the
 hash of his temporary public ECDH part, second party sends back their
 public ECDH part and then initiator sends his public ECDH part in
 open. All three messages are hashed together and the first two bytes
 are used to select two words from a shared dictionary which are
 displayed on the screen of both the initiator and the second party.

 The parties communicate those two words and verify they match.

How do they compare words if they haven't yet established a secure channel?

 If an attacker wants to do MITM, he has a chance of choosing right
 public parts 1:65536. There is no way to brute-force it, since that
 would be noticed immediately. If instead of two words based on the
 first two bytes, four words from BIP39 wordlist were chosen, it would
 provide entropy of 44 bits which I believe should be enough even for
 paranoid people.
 
 How this would work in Bitcoin payment scenario: user's phone
 broadcasts his name, merchant inputs amount and selects the name from
 the list, commit message is sent (and then the remaining two
 messages), merchant spells four words he sees on the screen and buyer
 confirms transaction after verifying that words match.

So the assumption is that there exists a secure (as in proximity-based)
communication channel?

e

 2015-02-06 0:46 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can resolve the
 integrity issues, but because of the public nature of the broadcast
 coupled with strong public identity, the privacy compromise is much
 worse. Now transactions are cryptographically tainted.

 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication, desktop,
 datacenter, etc., can capture payment requests and strongly correlate
 transactions to identities in an automated manner. The payment request
 must be kept private between the parties, and that's hard to do.

 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard to
 spoof thanks to commit protocol - see RedPhone)?

 Hi Martin,

 The problem is that you need to verify the ownership of the public key.
 A MITM can substitute the key. If you don't have verifiable identity
 associated with the public key (PKI/WoT), you need a shared secret (such
 as a secret phrase). But the problem is then establishing that secret
 over a public channel.

 You can bootstrap a private session over the untrusted network using a
 trusted public key (PKI/WoT). But the presumption is that you are
 already doing this over the web (using TLS). That process is subject to
 attack at the CA. WoT is not subject to a CA attack, because it's
 decentralized. But it's also not sufficiently deployed for some scenarios.

 e




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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Martin Habovštiak
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512

I believe, we are still talking about transactions of physical people in 
physical world. So yes, it's proximity based - people tell the words by mouth. 
:)

In case of RedPhone, you read those words verbally over not-yet-verified 
channel relying on difficulty of spoofing your voice. Also the app remembers 
the public keys, so you don't need to verify second time.

I suggest you to try RedPhone (called Signal on iPhone) yourself. It's 
free/open source, Internet-based and end-to-end encrypted. You may find it 
useful some day. Also I'm willing to help you with trying it after I wake up. 
(~8 hours: Send me private e-mail if you want to.)

Dňa 6. februára 2015 1:22:23 CET používateľ Eric Voskuil e...@voskuil.org 
napísal:

On 02/05/2015 04:04 PM, MⒶrtin HⒶboⓋštiak wrote:
 That's exactly what I though when seeing the RedPhone code, but after
 I studied the commit protocol I realized it's actually secure and
 convenient way to do it. You should do that too. :)

I was analyzing the model as you described it to me. A formal analysis
of the security model of a particular implementation, based on
inference
from source code, is a bit beyond what I signed up for. But I'm
perfectly willing to comment on your description of the model if you
are
willing to indulge me.

 Shortly, how it works:
 The initiator of the connection sends commit message containing the
 hash of his temporary public ECDH part, second party sends back their
 public ECDH part and then initiator sends his public ECDH part in
 open. All three messages are hashed together and the first two bytes
 are used to select two words from a shared dictionary which are
 displayed on the screen of both the initiator and the second party.

 The parties communicate those two words and verify they match.

How do they compare words if they haven't yet established a secure
channel?

 If an attacker wants to do MITM, he has a chance of choosing right
 public parts 1:65536. There is no way to brute-force it, since that
 would be noticed immediately. If instead of two words based on the
 first two bytes, four words from BIP39 wordlist were chosen, it would
 provide entropy of 44 bits which I believe should be enough even for
 paranoid people.

 How this would work in Bitcoin payment scenario: user's phone
 broadcasts his name, merchant inputs amount and selects the name from
 the list, commit message is sent (and then the remaining two
 messages), merchant spells four words he sees on the screen and buyer
 confirms transaction after verifying that words match.

So the assumption is that there exists a secure (as in proximity-based)
communication channel?

e

 2015-02-06 0:46 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can
resolve the
 integrity issues, but because of the public nature of the
broadcast
 coupled with strong public identity, the privacy compromise is
much
 worse. Now transactions are cryptographically tainted.

 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication,
desktop,
 datacenter, etc., can capture payment requests and strongly
correlate
 transactions to identities in an automated manner. The payment
request
 must be kept private between the parties, and that's hard to do.

 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would
send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit
protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard
to
 spoof thanks to commit protocol - see RedPhone)?

 Hi Martin,

 The problem is that you need to verify the ownership of the public
key.
 A MITM can substitute the key. If you don't have verifiable identity
 associated with the public key (PKI/WoT), you need a shared secret
(such
 as a secret phrase). But the problem is then establishing that
secret
 over a public channel.

 You can bootstrap a private session over the untrusted network using
a
 trusted public key (PKI/WoT). But the presumption is that you are
 already doing this over the web (using TLS). That process is subject
to
 attack at the CA. WoT is not subject to a CA attack, because it's
 decentralized. But it's also not sufficiently deployed for some
scenarios.

 e


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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Roy Badami
For peer-to-peer payments, how common do we think that the payment is
of an ad hoc nature rather than to a known contact?

If I want to pay my friends/colleagues/etc over a restaurant table
there's no reason why I couldn't already have their public keys in my
contact list - then it would be pretty straightforward to have a
watertight mechanism where I would know who I was paying.  You could
probably even relatively securely bootstrap a key exchange over SMS,
relying only on the contacts already having each other in their
phonebooks.

As for comsumer-to-merchant transactions where the merchant is a
bricks and mortar merchant, IMHO it absolutely has to be pay that
terminal over there.  It's the trust model we all currently use -
whether paying cash or card - and it's the only trust model that works
IMHO (and customers and businesses alike are well aware of the risks
of a fraudster standing behind the counter pretending to be an
employee accepting payment - and by and large are pretty good at
mitigating it).  OTOH as we've discussed here before there are many
use cases where the custoemr doesn't actually know or care about the
name of the shop or bar they walked into but is pretty damn sure that
they need to make payment to the person over there behind the counter.

Granted, there are cases taht dont' fall into either of the above -
but they're the cases that are (a) harder to figure out how to
authenticate and consequently (b) the use cases that are going to be
most subject to attempted fraud.

roy

On Thu, Feb 05, 2015 at 03:02:56PM -0800, William Swanson wrote:
 On Thu, Feb 5, 2015 at 2:10 PM, Eric Voskuil e...@voskuil.org wrote:
  A MITM can receive the initial broadcast and then spoof it by jamming the
  original. You then only see one.
 
 You are right, of course. There is no way to make Bluetooth 100%
 secure, since it is an over-the-air technology. You could try securing
 it using a CA or other identity server, but now you've excluded ad-hoc
 person-to-person payments. Plus, you need an active internet
 connection to reach the CA.
 
 You can try using proximity as a substitute for identity, like
 requiring NFC to kick-start the connection, but at that point you
 might as well use QR codes.
 
 This BIP is not trying to provide absolute bullet-proof security,
 since that's impossible given the physical limitations of the
 Bluetooth technology. Instead, it's trying to provide the
 best-possible security given those constraints. In exchange for this,
 we get greatly enhanced usability in common scenarios.
 
 There are plenty of usable, real-world technologies with big security
 holes. Anybody with lock-picking experience will tell you this, but
 nobody is welding their front door shut. The ability to go in and out
 is worth the security risk.
 
 Bluetooth payments add a whole new dimension to real-world Bitcoin
 usability. Do we shut that down because it can't be made perfect, or
 do we do the best we can and move forward?
 
 -William
 
 --
 Dive into the World of Parallel Programming. The Go Parallel Website,
 sponsored by Intel and developed in partnership with Slashdot Media, is your
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 leadership blogs to news, videos, case studies, tutorials and more. Take a
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Martin Habovštiak
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512

Commit protocol provides both better user experience and better security.

Dňa 6. februára 2015 1:49:12 CET používateľ Paul Puey p...@airbitz.co napísal:
The trust can be considered bootstrapped by visual verification of the
address prefix. If we are really concerned about someone jamming a
Bluetooth signal in a coffeeshop then the UI can encourage verification
of the prefix. Much like how regular Bluetooth requires 'pairing' via
entering a 4-6 digit code.



Paul Puey CEO / Co-Founder, Airbitz Inc
619.850.8624 | http://airbitz.co | San Diego




On Feb 5, 2015, at 3:46 PM, Eric Voskuil e...@voskuil.org wrote:

On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can resolve
the
 integrity issues, but because of the public nature of the broadcast
 coupled with strong public identity, the privacy compromise is much
 worse. Now transactions are cryptographically tainted.

 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication,
desktop,
 datacenter, etc., can capture payment requests and strongly
correlate
 transactions to identities in an automated manner. The payment
request
 must be kept private between the parties, and that's hard to do.

 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard to
 spoof thanks to commit protocol - see RedPhone)?

Hi Martin,

The problem is that you need to verify the ownership of the public key.
A MITM can substitute the key. If you don't have verifiable identity
associated with the public key (PKI/WoT), you need a shared secret
(such
as a secret phrase). But the problem is then establishing that secret
over a public channel.

You can bootstrap a private session over the untrusted network using a
trusted public key (PKI/WoT). But the presumption is that you are
already doing this over the web (using TLS). That process is subject to
attack at the CA. WoT is not subject to a CA attack, because it's
decentralized. But it's also not sufficiently deployed for some
scenarios.

e

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
On 02/05/2015 04:49 PM, Paul Puey wrote:
 The trust can be considered bootstrapped by visual verification of the
 address prefix.

Another (unspendable) address can trivially match the prefix. Imagine
someone walking around in a mall with a phone in the pocket with a
malicious app, just disrupting business by causing money to be burned.
Manual verification doesn't fix this attack.

 If we are really concerned about someone jamming a Bluetooth signal
 in a coffeeshop then the UI can encourage verification of the prefix.

I don't think it would be great to constrain a standard implementation
to low cost purchases or the need for manual verification, but again
manual prefix verification isn't actually a solution.

 Much like how regular Bluetooth requires 'pairing' via entering a 4-6
 digit code.

An appeal to the security of BT bootstrapping isn't exactly flattering.

You know I love Airbitz, and I know you guys are extremely privacy
conscious. I personally would have no problem using this feature under
certain circumstances. My question is only whether it would be wise to
standardize on the proposal as-is.

e

 On Feb 5, 2015, at 3:46 PM, Eric Voskuil e...@voskuil.org
 mailto:e...@voskuil.org wrote:
 
 On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can resolve the
 integrity issues, but because of the public nature of the broadcast
 coupled with strong public identity, the privacy compromise is much
 worse. Now transactions are cryptographically tainted.

 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication, desktop,
 datacenter, etc., can capture payment requests and strongly correlate
 transactions to identities in an automated manner. The payment request
 must be kept private between the parties, and that's hard to do.

 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard to
 spoof thanks to commit protocol - see RedPhone)?
 
 Hi Martin,
 
 The problem is that you need to verify the ownership of the public key.
 A MITM can substitute the key. If you don't have verifiable identity
 associated with the public key (PKI/WoT), you need a shared secret (such
 as a secret phrase). But the problem is then establishing that secret
 over a public channel.
 
 You can bootstrap a private session over the untrusted network using a
 trusted public key (PKI/WoT). But the presumption is that you are
 already doing this over the web (using TLS). That process is subject to
 attack at the CA. WoT is not subject to a CA attack, because it's
 decentralized. But it's also not sufficiently deployed for some scenarios.
 
 e
 



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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
Although consumer to merchant is a use case for BLE I would argue that NFC has 
a higher chance of providing a better user experience in most cases since, at 
least on Android, a user can tap their phone without even having a wallet 
running. The URI handler will launch the wallet for them. However a dedicated, 
user facing, screen can give certainty that the user is connecting to the 
correct recipient. 

1. Because it can show an address prefix 
2. It can display the users nickname/handle upon connecting which is only sent 
to the merchant upon a point to point connection. Not a broadcast. 

The Airbitz wallet already does this on the recipient side. A popup shows the 
most recent person connecting to the recipient. 


   
Paul Puey CEO / Co-Founder, Airbitz Inc
619.850.8624 | http://airbitz.co | San Diego
 



On Feb 5, 2015, at 3:34 PM, Roy Badami r...@gnomon.org.uk wrote:

For peer-to-peer payments, how common do we think that the payment is
of an ad hoc nature rather than to a known contact?

If I want to pay my friends/colleagues/etc over a restaurant table
there's no reason why I couldn't already have their public keys in my
contact list - then it would be pretty straightforward to have a
watertight mechanism where I would know who I was paying.  You could
probably even relatively securely bootstrap a key exchange over SMS,
relying only on the contacts already having each other in their
phonebooks.

As for comsumer-to-merchant transactions where the merchant is a
bricks and mortar merchant, IMHO it absolutely has to be pay that
terminal over there.  It's the trust model we all currently use -
whether paying cash or card - and it's the only trust model that works
IMHO (and customers and businesses alike are well aware of the risks
of a fraudster standing behind the counter pretending to be an
employee accepting payment - and by and large are pretty good at
mitigating it).  OTOH as we've discussed here before there are many
use cases where the custoemr doesn't actually know or care about the
name of the shop or bar they walked into but is pretty damn sure that
they need to make payment to the person over there behind the counter.

Granted, there are cases taht dont' fall into either of the above -
but they're the cases that are (a) harder to figure out how to
authenticate and consequently (b) the use cases that are going to be
most subject to attempted fraud.

roy

 On Thu, Feb 05, 2015 at 03:02:56PM -0800, William Swanson wrote:
 On Thu, Feb 5, 2015 at 2:10 PM, Eric Voskuil e...@voskuil.org wrote:
 A MITM can receive the initial broadcast and then spoof it by jamming the
 original. You then only see one.
 
 You are right, of course. There is no way to make Bluetooth 100%
 secure, since it is an over-the-air technology. You could try securing
 it using a CA or other identity server, but now you've excluded ad-hoc
 person-to-person payments. Plus, you need an active internet
 connection to reach the CA.
 
 You can try using proximity as a substitute for identity, like
 requiring NFC to kick-start the connection, but at that point you
 might as well use QR codes.
 
 This BIP is not trying to provide absolute bullet-proof security,
 since that's impossible given the physical limitations of the
 Bluetooth technology. Instead, it's trying to provide the
 best-possible security given those constraints. In exchange for this,
 we get greatly enhanced usability in common scenarios.
 
 There are plenty of usable, real-world technologies with big security
 holes. Anybody with lock-picking experience will tell you this, but
 nobody is welding their front door shut. The ability to go in and out
 is worth the security risk.
 
 Bluetooth payments add a whole new dimension to real-world Bitcoin
 usability. Do we shut that down because it can't be made perfect, or
 do we do the best we can and move forward?
 
 -William
 
 --
 Dive into the World of Parallel Programming. The Go Parallel Website,
 sponsored by Intel and developed in partnership with Slashdot Media, is your
 hub for all things parallel software development, from weekly thought
 leadership blogs to news, videos, case studies, tutorials and more. Take a
 look and join the conversation now. http://goparallel.sourceforge.net/
 ___
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 Bitcoin-development@lists.sourceforge.net
 https://lists.sourceforge.net/lists/listinfo/bitcoin-development
 
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look and join the conversation now. 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
The trust can be considered bootstrapped by visual verification of the address 
prefix. If we are really concerned about someone jamming a Bluetooth signal in 
a coffeeshop then the UI can encourage verification of the prefix. Much like 
how regular Bluetooth requires 'pairing' via entering a 4-6 digit code.


   
Paul Puey CEO / Co-Founder, Airbitz Inc
619.850.8624 | http://airbitz.co | San Diego
 



On Feb 5, 2015, at 3:46 PM, Eric Voskuil e...@voskuil.org wrote:

On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can resolve the
 integrity issues, but because of the public nature of the broadcast
 coupled with strong public identity, the privacy compromise is much
 worse. Now transactions are cryptographically tainted.
 
 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication, desktop,
 datacenter, etc., can capture payment requests and strongly correlate
 transactions to identities in an automated manner. The payment request
 must be kept private between the parties, and that's hard to do.
 
 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard to
 spoof thanks to commit protocol - see RedPhone)?

Hi Martin,

The problem is that you need to verify the ownership of the public key.
A MITM can substitute the key. If you don't have verifiable identity
associated with the public key (PKI/WoT), you need a shared secret (such
as a secret phrase). But the problem is then establishing that secret
over a public channel.

You can bootstrap a private session over the untrusted network using a
trusted public key (PKI/WoT). But the presumption is that you are
already doing this over the web (using TLS). That process is subject to
attack at the CA. WoT is not subject to a CA attack, because it's
decentralized. But it's also not sufficiently deployed for some scenarios.

e

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sponsored by Intel and developed in partnership with Slashdot Media, is your
hub for all things parallel software development, from weekly thought
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Eric Voskuil
On 02/05/2015 04:36 PM, Martin Habovštiak wrote:
 I believe, we are still talking about transactions of physical
 people in physical world. So yes, it's proximity based - people
 tell the words by mouth. :)

Notice from my original comment:

 A MITM can substitute the key. If you don't have verifiable
 identity associated with the public key (PKI/WoT), you need
 a shared secret (such as a secret phrase).

I said this could only be accomplished using a shared secret or a
trusted public key. Exchanging a value that is derived from a pair of
public keys is a distinction without a difference. The problem remains
that the parties must have a secure/out-of-band channel for
communicating this value.

The fact that they are face-to-face establishes this channel, but that
brings us back to the original problem, as it requires manual
verification - as in visual/audible scanning of the two values for
comparison. At that point the visual comparison of the address, or some
value derived from it, is simpler.

 In case of RedPhone, you read those words verbally over not-yet-
 verified channel relying on difficulty of spoofing your voice. Also
 the app remembers the public keys, so you don't need to verify
 second time.

This is reasonable, but wouldn't help in the case of an ad-hoc
connection between parties who don't know each other well.

 I suggest you to try RedPhone (called Signal on iPhone) yourself.
 It's free/open source, Internet-based and end-to-end encrypted. You
 may find it useful some day. Also I'm willing to help you with
 trying it after I wake up. (~8 hours: Send me private e-mail if
 you want to.)

I appreciate the offer. I really don't trust *any* smartphone as a
platform for secure communication/data. But encrypting on the wire does
of course shrink the attack surface and increase the attacker's cost.

e

 Dňa 6. februára 2015 1:22:23 CET používateľ Eric Voskuil
e...@voskuil.org napísal:

 On 02/05/2015 04:04 PM, MⒶrtin HⒶboⓋštiak wrote:
 That's exactly what I though when seeing the RedPhone code, but after
 I studied the commit protocol I realized it's actually secure and
 convenient way to do it. You should do that too. :)
 
 I was analyzing the model as you described it to me. A formal analysis
 of the security model of a particular implementation, based on
 inference
from source code, is a bit beyond what I signed up for. But I'm
 perfectly willing to comment on your description of the model if you
 are
 willing to indulge me.
 
 Shortly, how it works:
 The initiator of the connection sends commit message containing the
 hash of his temporary public ECDH part, second party sends back their
 public ECDH part and then initiator sends his public ECDH part in
 open. All three messages are hashed together and the first two bytes
 are used to select two words from a shared dictionary which are
 displayed on the screen of both the initiator and the second party.
 
 The parties communicate those two words and verify they match.
 
 How do they compare words if they haven't yet established a secure
 channel?
 
 If an attacker wants to do MITM, he has a chance of choosing right
 public parts 1:65536. There is no way to brute-force it, since that
 would be noticed immediately. If instead of two words based on the
 first two bytes, four words from BIP39 wordlist were chosen, it would
 provide entropy of 44 bits which I believe should be enough even for
 paranoid people.

 How this would work in Bitcoin payment scenario: user's phone
 broadcasts his name, merchant inputs amount and selects the name from
 the list, commit message is sent (and then the remaining two
 messages), merchant spells four words he sees on the screen and buyer
 confirms transaction after verifying that words match.
 
 So the assumption is that there exists a secure (as in proximity-based)
 communication channel?
 
 e
 
 2015-02-06 0:46 GMT+01:00 Eric Voskuil e...@voskuil.org:
 On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can
 resolve the
 integrity issues, but because of the public nature of the
 broadcast
 coupled with strong public identity, the privacy compromise is
 much
 worse. Now transactions are cryptographically tainted.

 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication,
 desktop,
 datacenter, etc., can capture payment requests and strongly
 correlate
 transactions to identities in an automated manner. The payment
 request
 must be kept private between the parties, and that's hard to do.

 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would
 send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit
 protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard
 to
 spoof thanks to commit protocol - see RedPhone)?

 Hi 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
Thanks for all the feedback Eric. You know we value all that you have to say. 
That's what this forum is for. We're looking for great ideas to harden this 
protocol and we're not closed to better ideas and we'll improve it as 
suggestions come up.



   
Paul Puey CEO / Co-Founder, Airbitz Inc
619.850.8624 | http://airbitz.co | San Diego
 



On Feb 5, 2015, at 5:05 PM, Eric Voskuil e...@voskuil.org wrote:

 On 02/05/2015 04:49 PM, Paul Puey wrote:
 The trust can be considered bootstrapped by visual verification of the
 address prefix.

Another (unspendable) address can trivially match the prefix. Imagine
someone walking around in a mall with a phone in the pocket with a
malicious app, just disrupting business by causing money to be burned.
Manual verification doesn't fix this attack.

 If we are really concerned about someone jamming a Bluetooth signal
 in a coffeeshop then the UI can encourage verification of the prefix.

I don't think it would be great to constrain a standard implementation
to low cost purchases or the need for manual verification, but again
manual prefix verification isn't actually a solution.

 Much like how regular Bluetooth requires 'pairing' via entering a 4-6
 digit code.

An appeal to the security of BT bootstrapping isn't exactly flattering.

You know I love Airbitz, and I know you guys are extremely privacy
conscious. I personally would have no problem using this feature under
certain circumstances. My question is only whether it would be wise to
standardize on the proposal as-is.

e

 On Feb 5, 2015, at 3:46 PM, Eric Voskuil e...@voskuil.org
 mailto:e...@voskuil.org wrote:
 
 On 02/05/2015 03:36 PM, MⒶrtin HⒶboⓋštiak wrote:
 A BIP-70 signed payment request in the initial broadcast can resolve the
 integrity issues, but because of the public nature of the broadcast
 coupled with strong public identity, the privacy compromise is much
 worse. Now transactions are cryptographically tainted.
 
 This is also the problem with BIP-70 over the web. TLS and other
 security precautions aside, an interloper on the communication, desktop,
 datacenter, etc., can capture payment requests and strongly correlate
 transactions to identities in an automated manner. The payment request
 must be kept private between the parties, and that's hard to do.
 
 What about using encryption with forward secrecy? Merchant would
 generate signed request containing public ECDH part, buyer would send
 back transaction encrypted with ECDH and his public ECDH part. If
 receiving address/amount is meant to be private, use commit protocol
 (see ZRTP/RedPhone) and short authentication phrase (which is hard to
 spoof thanks to commit protocol - see RedPhone)?
 
 Hi Martin,
 
 The problem is that you need to verify the ownership of the public key.
 A MITM can substitute the key. If you don't have verifiable identity
 associated with the public key (PKI/WoT), you need a shared secret (such
 as a secret phrase). But the problem is then establishing that secret
 over a public channel.
 
 You can bootstrap a private session over the untrusted network using a
 trusted public key (PKI/WoT). But the presumption is that you are
 already doing this over the web (using TLS). That process is subject to
 attack at the CA. WoT is not subject to a CA attack, because it's
 decentralized. But it's also not sufficiently deployed for some scenarios.
 
 e

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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
The BIP70 protocol would preclude individuals from utilizing the P2P
transfer spec. It would also require that a Sender have internet
connectivity to get the payment protocol info. BLE could enable payment w/o
internet by first transferring the URI to from Recipient to Sender. Then in
the future, we could sign a Tx and send it over BLE back to the recipient
(who would still need internet to verify the Tx). This is an important use
case for areas with poor 3G/4G connectivity as I've experience myself.

Also, due to Android issues, NFC is incredibly clunky. The URI Sender is
required to tap the screen *while* the two phones are in contact. We
support NFC the same way Bitcoin Wallet does, but unless the payment
recipient has a custom Android device (which a merchant might) then the
usage model is worse than scanning a QR code. BLE also allows people to pay
at a distance such as for a donation to a live performer. We'll look at
adding this to the Motivation section.

[image: logo]
*Paul Puey* CEO / Co-Founder, Airbitz Inc
+1-619-850-8624 | http://airbitz.co | San Diego
http://facebook.com/airbitz  http://twitter.com/airbitz
https://plus.google.com/118173667510609425617
https://go.airbitz.co/comments/feed/  http://linkedin.com/in/paulpuey
https://angel.co/paul-puey
*DOWNLOAD THE AIRBITZ WALLET:*
  https://play.google.com/store/apps/details?id=com.airbitz
https://itunes.apple.com/us/app/airbitz/id843536046


From: Andreas Schildbach andreas@sc... - 2015-02-05 13:47:04

Thanks Paul, for writing up your protocol!

First thoughts:

For a BIP standard, I think we should skip bitcoin: URIs entirely and
publish BIP70 payment requests instead. URIs mainly stick around because
of QR codes limited capacity. BIP70 would partly address the copycat
problem by signing payment requests.

In your Motivation section, I miss some words about NFC. NFC already
addresses all of the usability issues mentioned and is supported by
mobile wallets since 2011. That doesn't mean your method doesn't make
sense in some situations, but I think it should be explained why to
prefer broadcasting payment requests over picking them up via near field
radio.
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Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Paul Puey
Thanks for CC'ing me Mike. Having trouble receiving maillist list posts.

Even if a user could get the BIP70 URL in the URI, they would still need
internet to access the URL. This BLE spec doesn't preclude BIP70, but can
work with it while still allowing individuals without a certificate to
broadcast a request.

The issue of confused payments becomes less so if the Recipient broadcasts
a name along with the 10 digit public addr prefix. Only if there is a name
conflict will the user have to be concerned with the prefix. The name can
be something like

Mikes Coffee #1 and it can have a Register #1 at the counter. A customer
facing screen can also show the 10 digit prefix.


[image: logo]
*Paul Puey* CEO / Co-Founder, Airbitz Inc
+1-619-850-8624 | http://airbitz.co | San Diego
http://facebook.com/airbitz  http://twitter.com/airbitz
https://plus.google.com/118173667510609425617
https://go.airbitz.co/comments/feed/  http://linkedin.com/in/paulpuey
https://angel.co/paul-puey
*DOWNLOAD THE AIRBITZ WALLET:*
  https://play.google.com/store/apps/details?id=com.airbitz
https://itunes.apple.com/us/app/airbitz/id843536046




On Thu, Feb 5, 2015 at 12:28 PM, Mike Hearn m...@plan99.net wrote:

 BIP70 requests can be sent over bluetooth as well, as can transactions.
 Bitcoin Wallet can already send money even when offline by doing this. It's
 transparent to the user. I mean original Bluetooth in this context - BLE
 has incredibly tight data constraints and isn't really meant for data
 transfer.

 Yes Android Beam has a pretty stupid UI. You can actually tap the devices,
 take them away and then press, but that's not obvious at all. There have
 been new APIs added in recent releases that give more control over this, so
 it's possible we can revisit things and make the UI better these days.

 The donation to live performer example is good - there's no issue of
 accidentally paying for someone else in this context as there's only one
 recipient, but many senders.

 The issue of confused payments remains in other situations though.

 For the coffee shop use case, it'd be nicer (I think) if we aim for a
 Square-style UI where the device broadcasts a (link to) a photo of the user
 combined with a bluetooth MAC. Then the merchant tablet can show faces of
 people in the shop, and can push a payment request to the users device.
 That device can then buzz the user, show a confirmation screen, put
 something on their smart watch etc or just auto-authorise the payment
 because the BIP70 signature is from a trusted merchant. User never even
 needs to touch their phone at all.

 On Thu, Feb 5, 2015 at 9:06 PM, Paul Puey p...@airbitz.co wrote:

 The BIP70 protocol would preclude individuals from utilizing the P2P
 transfer spec. It would also require that a Sender have internet
 connectivity to get the payment protocol info. BLE could enable payment w/o
 internet by first transferring the URI to from Recipient to Sender. Then in
 the future, we could sign a Tx and send it over BLE back to the recipient
 (who would still need internet to verify the Tx). This is an important use
 case for areas with poor 3G/4G connectivity as I've experience myself.

 Also, due to Android issues, NFC is incredibly clunky. The URI Sender is
 required to tap the screen *while* the two phones are in contact. We
 support NFC the same way Bitcoin Wallet does, but unless the payment
 recipient has a custom Android device (which a merchant might) then the
 usage model is worse than scanning a QR code. BLE also allows people to pay
 at a distance such as for a donation to a live performer. We'll look at
 adding this to the Motivation section.

 [image: logo]
 *Paul Puey* CEO / Co-Founder, Airbitz Inc
 +1-619-850-8624 | http://airbitz.co | San Diego
 http://facebook.com/airbitz  http://twitter.com/airbitz
 https://plus.google.com/118173667510609425617
 https://go.airbitz.co/comments/feed/  http://linkedin.com/in/paulpuey
   https://angel.co/paul-puey
 *DOWNLOAD THE AIRBITZ WALLET:*
   https://play.google.com/store/apps/details?id=com.airbitz
 https://itunes.apple.com/us/app/airbitz/id843536046


 From: Andreas Schildbach andreas@sc... - 2015-02-05 13:47:04

 Thanks Paul, for writing up your protocol!

 First thoughts:

 For a BIP standard, I think we should skip bitcoin: URIs entirely and
 publish BIP70 payment requests instead. URIs mainly stick around because
 of QR codes limited capacity. BIP70 would partly address the copycat
 problem by signing payment requests.

 In your Motivation section, I miss some words about NFC. NFC already
 addresses all of the usability issues mentioned and is supported by
 mobile wallets since 2011. That doesn't mean your method doesn't make
 sense in some situations, but I think it should be explained why to
 prefer broadcasting payment requests over picking them up via near field
 radio.




 --
 Dive into the World of Parallel Programming. The Go 

Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

2015-02-05 Thread Mike Hearn

 Even if a user could get the BIP70 URL in the URI, they would still need
 internet to access the URL.


The way Bitcoin Wallet does it, the bitcoin URI includes a MAC address
where you can download the request from. BIP70 does not depend on internet
access or HTTP, plus, you don't have to sign them.

The name field might work but requires the merchant to set it, e.g. by
asking the payer what their name is, then typing it in, then the payer has
to wait for it to show up. By this point it's probably faster to have
scanned a QR code.

Re: security. I'll repeat what I wrote up-thread in case you didn't see it:

it's not clear to me at all that this partial address scheme is actually
 secure. The assumption appears to be that the MITM must match the address
 prefix generated by the genuine merchant. But if they can do a wireless
 MITM they can just substitute their own address prefix/partial address, no?

 To avoid MITM attacks the sender must know who they are sending money to,
 and that means they must see a human understandable name that's
 cryptographically bound to the right public key. Displaying partial
 addresses to the user is not going to solve this unless users manually
 compare key prefixes across the screens which is even less convenient
 than a QR code.

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