Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Gregory Maxwell
On Fri, Jan 23, 2015 at 4:18 PM, slush sl...@centrum.cz wrote:
 Can you send me any reference about this? Of course if that solves the
 problem, hard fork would not be necessary anymore. I'm just not aware of
 any.

Sure; will aggregate up the citations when I'm not travling later today.

 To sign transaction with hundreds of inputs on device with limited memory
 capabilities, I need to stream all previous transactions into device, for
 every signed input.

 That means roughly 200^2 transaction verifications for 200 inputs to sign.
 Very slow, but does not limit the device for any particular size of signed
 transaction.

I'm not sure where the ^2 is coming from.  So what I'd understand that
you'd do is stream in the input txid:vouts which you spend, then you'd
stream the actual inputs which would just be hashed and value
extracted (but no other verification), and you'd build a table of
txid:vout-value, then the actual transaction to be signed.

This should have O(inputs) hashing and communications overhead. Is
there a step I'm missing?

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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Peter Todd
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA256



On 23 January 2015 08:35:23 GMT-08:00, slush sl...@centrum.cz wrote:
Oh, now I got the 'soft-fork' alternative. If that means that *senders*
to
Trezor need to be nice guys and use some special outputs, then it's,
obviously, no-go solution.

That's what P2SH is for; the senders will just be sending to a P2SH address.

I understand political aspect around hard-fork. Anyway, are there any
other
pending projects waiting for hard-fork?

Hard-forks aren't hard for directly political issues, they're politically hard 
because they're risky by requiring everyone yo upgrade at once. In the case of 
signature validation, that touches a *lot* of third party code that people rely 
on to avoid being defrauded.

FWIW I've actually got a half-finished writeup for how to use OP_CODESEPARATOR 
and a CHECKSIG2 soft-fork to have signatures sign fees and so forth.
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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Alan Reiner

On 01/23/2015 11:27 AM, Alan Reiner wrote:

 I am happy to entertain other ideas that achieve our goals here, but I'm
 fairly confident that the new SIGHASH type is the only way that would
 allow devices like Trezor to truly simplify their design (and still work
 securely on 100% of funds contained by the wallet).

 
Self-correction ... I didn't mean it's the only way, I mean it's by
far the easiest, simplest, least-intrusive way that achieves the
properties we need for this to be useful.

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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread slush
Oh, now I got the 'soft-fork' alternative. If that means that *senders* to
Trezor need to be nice guys and use some special outputs, then it's,
obviously, no-go solution.

I understand political aspect around hard-fork. Anyway, are there any other
pending projects waiting for hard-fork? Maybe we should join our effort in
some way.

M.

On Fri, Jan 23, 2015 at 5:27 PM, Alan Reiner etothe...@gmail.com wrote:


 I am happy to entertain other ideas that achieve our goals here, but I'm
 fairly confident that the new SIGHASH type is the only way that would
 allow devices like Trezor to truly simplify their design (and still work
 securely on 100% of funds contained by the wallet).



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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Tamas Blummer
Not a fix, but would reduce the financial risk, if nodes were not relaying 
excessive fee transactions.

Tamas Blummer



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[Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread slush
Hi,

is any progress or even discussion in this area?

https://bitcointalk.org/index.php?topic=181734.0

I don't insist on any specific solution, but this is becoming a real issue
as hardware wallets are more widespread. I'm sitting next to TREZOR for 40
minutes already, because it streams and validate some complex transaction.
By using proposed solution, such signature would be a matter of few seconds.

That's also not just about time/resource/hw cost optimization. I'm talking
about possibility of huge simplification of the firmware (=security FTW),
because 50% of actual codebase is solving this particular downside of
Bitcoin protocol.

So, there's real world problem. On which solution can we as a community
find a wide agreement?

Best,
Marek
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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Gregory Maxwell
On Fri, Jan 23, 2015 at 3:24 PM, Alan Reiner etothe...@gmail.com wrote:
 Unfortunately, it seems that there was no soft-fork way to achieve this
 benefit, at least not one that had favorable properties.  Most of the
 soft-fork variations of it required the coins being spent to have been
 originated in a special way.  In other words, it would only work if the
 coins had entered the wallet with some special, modified TxOut script.  So
 it wouldn't work with existing coins, and would require senders to update
 their software to reshape the way they send transactions to be compatible
 with our goals.

I think this is unreasonable. There is a straight-forward soft-fork
approach which is safe (e.g. no risk of invalidating existing
transactions). Yes, it means that you need to use newly created
addresses to get coins that use the new signature type... but thats
only the case for people who want the new capability. This is
massively preferable to expecting _every_ _other_ user of the system
(including miners, full nodes, etc.) to replace their software with an
incompatible new version just to accommodate your transactions, for
which they may care nothing about and which would otherwise not have
any urgent need to change.

I've expected this need to be addressed simply as a side effect of a
new, more efficient, checksig operator which some people have been
working on and off on but which has taken a backseat to other more
urgent issues.

On Fri, Jan 23, 2015 at 2:51 PM, slush sl...@centrum.cz wrote:
 as hardware wallets are more widespread. I'm sitting next to TREZOR for 40
 minutes already, because it streams and validate some complex transaction.

Can you help me understand whats taking 40 minutes here? Thats a
surprisingly high number, and so I'm wondering if I'm not missing
something there.

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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Alan Reiner
Unfortunately, one major attack vector is someone isolating your node,
getting you to sign away your whole wallet to fee, and then selling it
to a mining pool to mine it before you can figure why your transactions
aren't making it to the network.  In such an attack, the relay rules
aren't relevant, and if the attacker can DoS you for 24 hours, it
doesn't take a ton of mining power to make the attack extremely likely
to succeed.




On 01/23/2015 10:31 AM, Tamas Blummer wrote:
 Not a fix, but would reduce the financial risk, if nodes were not
 relaying excessive fee transactions.

 Tamas Blummer



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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Adam Back
its an always offline node, so it knows nothing really other than a
BIP 32 hierarchy of keys  a signature request.

So the signature request has to drag with it information to validate
what the value is, in order to be sure not to sign away 99% to fees.
Signing the transaction value and having the network validate that the
value in the sig matches full nodes view of the tx value avoids that
issue.  Simple, elegant, but... we have no live beta mechanism, and
hence risk  testing makes that tricky.  Plus the full network upgrade
issue if its not backwards compatible.

Adam

On 23 January 2015 at 16:08, Tamas Blummer ta...@bitsofproof.com wrote:
 You mean an isolated signing device without memory right?

 An isolated node would still know the transactions substantiating its coins,
 why would it sign them away to fees ?

 Tamas Blummer

 On Jan 23, 2015, at 4:47 PM, slush sl...@centrum.cz wrote:

 Correct, plus the most likely scenario in such attack is that the malware
 even don't push such tx with excessive fees to the network, but send it
 directly to attacker's pool/miner.

 M.

 On Fri, Jan 23, 2015 at 4:42 PM, Alan Reiner etothe...@gmail.com wrote:

 Unfortunately, one major attack vector is someone isolating your node,
 getting you to sign away your whole wallet to fee, and then selling it to a
 mining pool to mine it before you can figure why your transactions aren't
 making it to the network.  In such an attack, the relay rules aren't
 relevant, and if the attacker can DoS you for 24 hours, it doesn't take a
 ton of mining power to make the attack extremely likely to succeed.




 On 01/23/2015 10:31 AM, Tamas Blummer wrote:

 Not a fix, but would reduce the financial risk, if nodes were not relaying
 excessive fee transactions.

 Tamas Blummer






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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Alan Reiner
The SIGHASH_WITHINPUTVALUE proposal is a hardfork, but otherwise
non-intrusive, doesn't change any TxOut scripts, doesn't change any
tx/block parsing (besides verification), it works with all existing
coins in the network, and existing software doesn't have to use it if
they don't want to upgrade their signers.   The proposal simply provides
a way to optionally sign the input values with the TxOut scripts.  In
other words a signature right now says I sign this transaction using
these inputs, whatever value they are.  With this SIGHASH type, the
signature says I sign this transaction assuming that input 0 is X BTC,
input 1 is Y BTC,.  If the online computer providing the data to be
signed lies about the value of any input, the resulting signature will
be invalid.

Unfortunately, it seems that there was no soft-fork way to achieve this
benefit, at least not one that had favorable properties.  Most of the
soft-fork variations of it required the coins being spent to have been
originated in a special way.  In other words, it would only work if the
coins had entered the wallet with some special, modified TxOut script. 
So it wouldn't work with existing coins, and would require senders to
update their software to reshape the way they send transactions to be
compatible with our goals.

I *strongly* encourage this to be considered for inclusion at some
point.  Not only does it simplify HW as Marek suggested, it increases
the options for online-offline communication channels, which is also a
win for security.  Right now, QR codes don't work because of the
possibility of having to transfer megabytes over the channel, and no way
to for the signer to control that size.  With this change, it's possible
for the signer to control the size of each chunk of data to guarantee it
fits in, say, a QR code (even if it means breaking it up into a couple
smaller transactions).

-Alan



On 01/23/2015 09:51 AM, slush wrote:
 Hi,

 is any progress or even discussion in this area? 

 https://bitcointalk.org/index.php?topic=181734.0

 I don't insist on any specific solution, but this is becoming a real
 issue as hardware wallets are more widespread. I'm sitting next to
 TREZOR for 40 minutes already, because it streams and validate some
 complex transaction. By using proposed solution, such signature would
 be a matter of few seconds.

 That's also not just about time/resource/hw cost optimization. I'm
 talking about possibility of huge simplification of the firmware
 (=security FTW), because 50% of actual codebase is solving this
 particular downside of Bitcoin protocol.

 So, there's real world problem. On which solution can we as a
 community find a wide agreement?

 Best,
 Marek


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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread slush
 I *strongly* encourage this to be considered for inclusion at some point.

Thanks Alan for a nice summary. I also agree that such stuff should be
implemented at some point. Anyway, I would probably not vote for doing hard
fork *just* for this change, but if I remember well, there're other ideas
flying around in the air and waiting for hardfork...

Marek

On Fri, Jan 23, 2015 at 4:24 PM, Alan Reiner etothe...@gmail.com wrote:

  The SIGHASH_WITHINPUTVALUE proposal is a hardfork, but otherwise
 non-intrusive, doesn't change any TxOut scripts, doesn't change any
 tx/block parsing (besides verification), it works with all existing coins
 in the network, and existing software doesn't have to use it if they don't
 want to upgrade their signers.   The proposal simply provides a way to
 optionally sign the input values with the TxOut scripts.  In other words a
 signature right now says I sign this transaction using these inputs,
 whatever value they are.  With this SIGHASH type, the signature says I
 sign this transaction assuming that input 0 is X BTC, input 1 is Y
 BTC,.  If the online computer providing the data to be signed lies
 about the value of any input, the resulting signature will be invalid.

 Unfortunately, it seems that there was no soft-fork way to achieve this
 benefit, at least not one that had favorable properties.  Most of the
 soft-fork variations of it required the coins being spent to have been
 originated in a special way.  In other words, it would only work if the
 coins had entered the wallet with some special, modified TxOut script.  So
 it wouldn't work with existing coins, and would require senders to update
 their software to reshape the way they send transactions to be compatible
 with our goals.

 I *strongly* encourage this to be considered for inclusion at some
 point.  Not only does it simplify HW as Marek suggested, it increases the
 options for online-offline communication channels, which is also a win for
 security.  Right now, QR codes don't work because of the possibility of
 having to transfer megabytes over the channel, and no way to for the signer
 to control that size.  With this change, it's possible for the signer to
 control the size of each chunk of data to guarantee it fits in, say, a QR
 code (even if it means breaking it up into a couple smaller transactions).

 -Alan




 On 01/23/2015 09:51 AM, slush wrote:

 Hi,

  is any progress or even discussion in this area?

  https://bitcointalk.org/index.php?topic=181734.0

  I don't insist on any specific solution, but this is becoming a real
 issue as hardware wallets are more widespread. I'm sitting next to TREZOR
 for 40 minutes already, because it streams and validate some complex
 transaction. By using proposed solution, such signature would be a matter
 of few seconds.

  That's also not just about time/resource/hw cost optimization. I'm
 talking about possibility of huge simplification of the firmware (=security
 FTW), because 50% of actual codebase is solving this particular downside of
 Bitcoin protocol.

  So, there's real world problem. On which solution can we as a community
 find a wide agreement?

  Best,
 Marek


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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread slush
Correct, plus the most likely scenario in such attack is that the malware
even don't push such tx with excessive fees to the network, but send it
directly to attacker's pool/miner.

M.

On Fri, Jan 23, 2015 at 4:42 PM, Alan Reiner etothe...@gmail.com wrote:

  Unfortunately, one major attack vector is someone isolating your node,
 getting you to sign away your whole wallet to fee, and then selling it to a
 mining pool to mine it before you can figure why your transactions aren't
 making it to the network.  In such an attack, the relay rules aren't
 relevant, and if the attacker can DoS you for 24 hours, it doesn't take a
 ton of mining power to make the attack extremely likely to succeed.




 On 01/23/2015 10:31 AM, Tamas Blummer wrote:

 Not a fix, but would reduce the financial risk, if nodes were not relaying
 excessive fee transactions.

  Tamas Blummer





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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Tamas Blummer
You mean an isolated signing device without memory right? 

An isolated node would still know the transactions substantiating its coins, 
why would it sign them away to fees ?

Tamas Blummer

On Jan 23, 2015, at 4:47 PM, slush sl...@centrum.cz wrote:

 Correct, plus the most likely scenario in such attack is that the malware 
 even don't push such tx with excessive fees to the network, but send it 
 directly to attacker's pool/miner.
 
 M.
 
 On Fri, Jan 23, 2015 at 4:42 PM, Alan Reiner etothe...@gmail.com wrote:
 Unfortunately, one major attack vector is someone isolating your node, 
 getting you to sign away your whole wallet to fee, and then selling it to a 
 mining pool to mine it before you can figure why your transactions aren't 
 making it to the network.  In such an attack, the relay rules aren't 
 relevant, and if the attacker can DoS you for 24 hours, it doesn't take a ton 
 of mining power to make the attack extremely likely to succeed.
 
 
 
 
 On 01/23/2015 10:31 AM, Tamas Blummer wrote:
 Not a fix, but would reduce the financial risk, if nodes were not relaying 
 excessive fee transactions.
 
 Tamas Blummer
 
 
 
 



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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread slush
On Fri, Jan 23, 2015 at 5:05 PM, Gregory Maxwell gmaxw...@gmail.com wrote:

 I think this is unreasonable. There is a straight-forward soft-fork
 approach which is safe (e.g. no risk of invalidating existing
 transactions). Yes, it means that you need to use newly created
 addresses to get coins that use the new signature type...


Can you send me any reference about this? Of course if that solves the
problem, hard fork would not be necessary anymore. I'm just not aware of
any.

Can you help me understand whats taking 40 minutes here? Thats a
 surprisingly high number, and so I'm wondering if I'm not missing
 something there.


To sign transaction with hundreds of inputs on device with limited memory
capabilities, I need to stream all previous transactions into device, for
every signed input.

That means roughly 200^2 transaction verifications for 200 inputs to sign.
Very slow, but does not limit the device for any particular size of signed
transaction.

Marek
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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Alan Reiner

On 01/23/2015 11:05 AM, Gregory Maxwell wrote:
 On Fri, Jan 23, 2015 at 3:24 PM, Alan Reiner etothe...@gmail.com wrote:
 Unfortunately, it seems that there was no soft-fork way to achieve this
 benefit, at least not one that had favorable properties.  Most of the
 soft-fork variations of it required the coins being spent to have been
 originated in a special way.  In other words, it would only work if the
 coins had entered the wallet with some special, modified TxOut script.  So
 it wouldn't work with existing coins, and would require senders to update
 their software to reshape the way they send transactions to be compatible
 with our goals.
 I think this is unreasonable. There is a straight-forward soft-fork
 approach which is safe (e.g. no risk of invalidating existing
 transactions). Yes, it means that you need to use newly created
 addresses to get coins that use the new signature type... but thats
 only the case for people who want the new capability. This is
 massively preferable to expecting _every_ _other_ user of the system
 (including miners, full nodes, etc.) to replace their software with an
 incompatible new version just to accommodate your transactions, for
 which they may care nothing about and which would otherwise not have
 any urgent need to change.




As far as I'm concerned, anything that requires the coins to originate
in the wallet with some special form is a non-starter.  The new SIGHASH
type allows you to sign transactions with any coins already in your
wallet, and imposes no requirements on anyone paying your cold wallet. 
Any such proposals that require origination structure means that 100% of
people paying you need to be nice and use this new script type, or
else you *have* to

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Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE

2015-01-23 Thread Alan Reiner

On 01/23/2015 11:05 AM, Gregory Maxwell wrote:
 On Fri, Jan 23, 2015 at 3:24 PM, Alan Reiner etothe...@gmail.com wrote:
 Unfortunately, it seems that there was no soft-fork way to achieve this
 benefit, at least not one that had favorable properties.  Most of the
 soft-fork variations of it required the coins being spent to have been
 originated in a special way.  In other words, it would only work if the
 coins had entered the wallet with some special, modified TxOut script.  So
 it wouldn't work with existing coins, and would require senders to update
 their software to reshape the way they send transactions to be compatible
 with our goals.
 I think this is unreasonable. There is a straight-forward soft-fork
 approach which is safe (e.g. no risk of invalidating existing
 transactions). Yes, it means that you need to use newly created
 addresses to get coins that use the new signature type... but thats
 only the case for people who want the new capability. This is
 massively preferable to expecting _every_ _other_ user of the system
 (including miners, full nodes, etc.) to replace their software with an
 incompatible new version just to accommodate your transactions, for
 which they may care nothing about and which would otherwise not have
 any urgent need to change.




As far as I'm concerned, anything that requires the coins to originate
in the wallet with some special form is a non-starter.  The new SIGHASH
type allows you to sign transactions with *any* coins already in your
wallet, and imposes no requirements on anyone paying your cold wallet to
be compatible with your signer. 

Any proposals that require coin origination features means that 100% of
people paying you need to be nice and send you coins with this special
structure.  You can't spend old coins that were sent before this
proposal was implemented, and if anyone sends you coins without
respecting the new structure, then your signing devices need the
full-complexity routines to accommodate, which defeats the entire purpose.

I am happy to entertain other ideas that achieve our goals here, but I'm
fairly confident that the new SIGHASH type is the only way that would
allow devices like Trezor to truly simplify their design (and still work
securely on 100% of funds contained by the wallet).


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