Hi Tony, Andy,
Matt already answered most of your questions in the previous emails.
Here are additional answers to make sure this is clear enough.
> The interchanging between "bob" and "domain owner" is a bit confusing
> in your gist.
I'm not sure what interchanging you're referring to. Alice is the payer,
Bob is the payment recipient and is using a `domain.com
<http://domain.com>` address. None
of them are the domain owner in any of the examples (even though Bob
could decide to take that role).
> Are you saying with that option, all it takes is a single DNS entry
> for "serviceprovider.com <http://serviceprovider.com>" to service
unlimited users?
Yes, option 1 uses a single DNS record that ties a domain to a specific
lightning node. The payer then queries that lightning node to obtain an
offer from their intended recipient.
> I agree that option 3 and 1 should be used. However, you say "clients
> (mobile wallets) would first make a DNS request corresponding to
> option 3, and if that fails, they would fallback to option 1. Domain
> owners would implement only one of those two options, depending on
> their DNS capabilities." . However, it seems to me like if we query
> for a specific user at the domain and it exists, use Option 3, but if
> it doesn't, then fall back to Option 1. So, they can actually
> implement both, depending on the user.
Right, I meant that domain owners may choose to only implement option 1,
but if they have the capabilities to implement option 3, they can (and
probably should) also support option 1.
> I would omit suggesting to use DoH from the spec.
> [...]
> How you query DNS seems like that should be left up to the client and
> not really part of the spec.
That will likely just be a suggestion, not a requirement on the spec.
Note that this isn't a spec at all yet, just a design document.
> Is there a minimum path/offer expiry? Wondering if those might be way
> lower than the DNS record expiry? Seems like we want the expiry of the
> DNS record to be less than the path expiry because there will be some
> latency in propagating a record with a new blinded path or offer
> through an organization's redundant nameservers. Also, when you create
> the offer with an expiry and add it to the DNS record, that expiry is
> part of the offer data itself and relative to when it was *created*,
> but your local computer will have an expiry that starts at the time
> you *fetched* that DNS record.
Offers can be very long-lived (months/years), especially the ones that
should be used in those scenarios. I don't think this would be an issue
at all here.
> Will we hit any DNS record length limits with the blinded path or
> offer that need to be considered?
That is a good question, and we should strive to use offers that are
as small as possible. In practice those will contain a 1-hop blinded
path, so they will be small enough.
> I think you should also add an option for a type that allows different
> users to have different blinded paths.
That can be achieved by using subdomains and sharding your users across
subdomains. This should indeed be mentioned in the future spec.
> I think should be revised to not use "LSP". We don't necessarily know
> if it is an LSP or a self hosted domain and node. It could be an LSP,
> but maybe not.
Right, I tried to use "domain owner" in most places, but it's a bit
messy. I'll make the terminology clearer in the spec.
> Seems to be a bad idea to me. You are relying on certificate
> authorities to prove the ownership of a domain? The certificate
> authorities are not an authority on domain ownership. Also, it seems
> to me like certificate authorities are a major weak link because if
> *any* certificate authority in your local trust database becomes
> faulty, *all* certificates can no longer be trusted.
Agreed, as I mentioned in the post, I included this option to show how
we could achieve this using only lightning, but I don't think this
should be the chosen approach.
> "The statement "Note that Alice cannot verify that the offer she
> receives is really from Bob" can apply to this option too, right?
Yes, this has the same trust-on-first-use issue.
> The LNURL way still relies on DNS so I'm confused why you'd want to
> add a webserver into the mix if you don't have to.
I 100% agree with that (but not sure what you are responding to here).
Thanks for your feedback!
Bastien
Le lun. 20 nov. 2023 à 09:34, Matt Corallo <lf-li...@mattcorallo.com>
a écrit :
On 11/17/23 8:28 AM, Andy Schroder wrote:
> #Comments
>
>
> ## General
>
> - I agree that option 3 and 1 should be used. However, you say
"clients (mobile wallets) would first
> make a DNS request corresponding to option 3, and if that fails,
they would fallback to option 1.
> Domain owners would implement only one of those two options,
depending on their DNS capabilities." .
> However, it seems to me like if we query for a specific user at
the domain and it exists, use Option
> 3, but if it doesn't, then fall back to Option 1. So, they can
actually implement both, depending on
> the user.
Yea, option 1 could reasonably take precedence, however the
tradeoff in that case would be revealing
*who* you're paying, not just which service you're paying through,
to any (honest but curious) DoH
resolver.
> - I would omit suggesting to use DoH from the spec. DoH seems a
bit centralized to me and that's up
> to the client to decide what to do. DNS itself is a
hierarchically distributed system, so there is
> redundancy built into it (which has its flaw at the root
nameserver / ICANN level) and it seems to
> me like DoH is taking much of that distributed design away. It
seems like if you are concerned about
> your ISP snooping your traffic, you should use a tunnel so that
your traffic is obfuscated that way,
> that way things are done at the IP level and not way up at the
HTTPS level. Are you resorting to DoH
> because many ISP block traffic for DNSSEC records traffic
through their networks? Either way, how
> you query DNS seems like that should be left up to the client
and not really part of the spec.
It is, but its worth mentioning in large part because almost
certainly ~all implementations will use
it. While I agree that it'd be very nice to not use it, in order
to do so clients would need to (a)
actually be able to query TXT records, which isn't in standard
operating system libraries, so would
probably mean DoH to 127.0.0.53 or so, (b) trust the resolver's
DNSSEC validation, which means
having some confidence its local, and not a coffee shop/etc.
Given the level of trust you have to have here in the DNS
resolution, its almost certainly best to
cross-validate with at least multiple DoH services, unless you are
validating the DNSSEC chain
yourself (which I'd really strongly prefer as the best solution
here, but I'm unaware of any open
source code to do so).
> - Is there a minimum path/offer expiry? Wondering if those might
be way lower than the DNS record
> expiry? Seems like we want the expiry of the DNS record to be
less than the path expiry because
> there will be some latency in propagating a record with a new
blinded path or offer through an
> organization's redundant nameservers. Also, when you create the
offer with an expiry and add it to
> the DNS record, that expiry is part of the offer data itself and
relative to when it was *created*,
> but your local computer will have an expiry that starts at the
time you *fetched* that DNS record.
While offers can expire arbitrarily, I anticipate users of this
system will fetch long-lived offers,
eg ones that expire in a year or two.
> - Will we hit any DNS record length limits with the blinded path
or offer that need to be considered?
We certainly shouldn't. You can put a full PGP key in the DNS:
$ dig
4f31fa50e5bd5ff45684e560fc24aeee527a43739ab611c49c51098a._openpgpkey.mattcorallo.com
<http://openpgpkey.mattcorallo.com> type61
>
> ## Option 1
>
> I think you should also add an option for a type that allows
different users to have different
> blinded paths. From a scalability perspective, one may not want
to serve all users on the same node.
> Also, the user may use their own lightning node instead of the
domain operators.
>
> | hostname | record type | value | TTL |
>
|------------------------|-------------|---------------------|-------------|
> | bob._lnaddress.domain.com <http://lnaddress.domain.com>. |
TXT | path:<blinded_path> | path expiry |
>
>
> The statement
>
> "Note that Alice cannot verify that the offer she receives is
really from Bob: she has to TOFU
> (trust on first use). But that's something we fundamentally
cannot fix if the only information Alice
> has is `b...@domain.com`. However, Alice obtains a signed
statement from Bob's LSP that attests that
> `b...@domain.com` is associated with the Bolt12 offer she
receives. If she later discovers that this
> was invalid, she can publish that proof to show the world that
Bob's LSP is malicious"
>
> - I think should be revised to not use "LSP". We don't
necessarily know if it is an LSP or a self
> hosted domain and node. It could be an LSP, but maybe not.
>
> - I think we should say that we cannot verify the offer *if* Bob
does not self host and uses an LSP.
> If Bob self hosts, we know it's from Bob if DNSSEC validates and
the root nameservers and the tld
> nameservers are honest.
>
> - I think there should be a QR code format that accompanies this
so that phone apps can easily
> validate the path (or for option 3 below the offer).
>
>
> ## Option 2
>
>
> - Seems to be a bad idea to me. You are relying on certificate
authorities to prove the ownership of
> a domain? The certificate authorities are not an authority on
domain ownership. Also, it seems to me
> like certificate authorities are a major weak link because if
*any* certificate authority in your
> local trust database becomes faulty, *all* certificates can no
longer be trusted.
>
> - This approach seems *very* unscalable because it requires the
announcements for all domains to be
> gossiped to everyone? I think that there needs to be a
decentralized DNS that is created, but this
> seems to be headed in the wrong direction. We should be able to
learn from some of the hierarchical
> features of legacy DNS and build a truly decentralized "root",
which will be more efficient.
>
>
>
>
> ## Option 3
>
> - "The statement "Note that Alice cannot verify that the offer
she receives is really from Bob" can
> apply to this option too, right?
>
>
> Andy Schroder
>
> On 11/16/23 08:51, Bastien TEINTURIER wrote:
>> Good morning list,
>>
>> Most of you already know and love lightning addresses [1].
>> I wanted to revisit that protocol, to see how we could improve
it and
>> fix its privacy drawbacks, while preserving the nice UX
improvements
>> that it brings.
>>
>> I have prepared a gist with three different designs that
achieve those
>> goals [2]. I'm attaching the contents of that gist below. I'd
like to
>> turn it into a bLIP once I collect enough feedback from the
community.
>>
>> I don't think we should select and implement all three options.
They
>> show that we have a large enough design space, but I think we
should
>> aim for simplicity of implementation and deployment. My
personal choice
>> would be to do options 1 and 3: clients (mobile wallets) would
first
>> make a DNS request corresponding to option 3, and if that
fails, they
>> would fallback to option 1. Domain owners would implement only
one of
>> those two options, depending on their DNS capabilities.
>>
>> Curious to hear your thoughts!
>>
>> Many thanks to Rusty and Matt who reviewed early drafts of that
gist.
>>
>> [1] https://lightningaddress.com/
>> [2] https://gist.github.com/t-bast/78fd797a7da570d293a8663908d3339b
>>
>> # Lightning Address
>>
>> [Lightning Address](https://lightningaddress.com/) is a very
popular protocol that brings UX improvements that users love.
>> We'd like to provide those UX benefits without its privacy and
security drawbacks.
>>
>> ## Issues with the current lightning address protocol
>>
>> As described
[here](https://github.com/andrerfneves/lightning-address/blob/master/README.md),
the lightning address protocol requires payment senders to make an
HTTP request to the recipient's domain owner.
>> This has some inconvenient side effects:
>>
>> 1. The payment sender reveals their IP address to the
recipient's domain owner, who knows both the sender and the recipient.
>> 2. The domain owner can swap invoices to steal some of the payment.
>> 3. It introduces a dependency on DNS servers and the need for
an HTTP stack on the sender side.
>>
>> We can do better and fix or mitigate some of these issues,
without compromising on UX.
>> We need two somewhat distinct mechanisms:
>>
>> 1. A way to privately obtain the `node_id` associated with a
given domain.
>> 2. A way to privately contact that domain to obtain the
recipient's payment details.
>>
>> ## User story
>>
>> Alice wants to pay `b...@domain.com` without any other prior
information.
>> She doesn't want to reveal:
>>
>> * her identity to Bob (payment sender privacy)
>> * her identity to the manager of `domain.com
<http://domain.com> <http://domain.com>` (payment sender privacy)
>> * the fact that she wants to pay `b...@domain.com` to her LSP
(payment recipient privacy)
>>
>> ## Option 1: use DNS records to link domains to nodes
>>
>> A first proposal would be to use a DNS record to obtain the
`node_id` associated with a given domain.
>>
>> ### Obtain a blinded path to the node associated with a domain
>>
>> Domain owners add a DNS `TXT` record for their domain
containing a blinded path to their node.
>> They may include an empty path if they wish to directly reveal
their `node_id`.
>>
>> | hostname | record type | value | TTL
|
>>
|------------------------|-------------|---------------------|-------------|
>> | _lnaddress.domain.com <http://lnaddress.domain.com>
<http://lnaddress.domain.com>. | TXT | path:<blinded_path>
| path expiry |
>>
>> Alice can then make a DNS query to obtain that blinded path.
>>
>> ```text
>> Alice DNS server
>> | |
>> | dig TXT _lnaddress.domain.com
<http://lnaddress.domain.com> <http://lnaddress.domain.com>
|
>>
|-------------------------------------------------------------------->|
>> | _lnaddress.domain.com
<http://lnaddress.domain.com> <http://lnaddress.domain.com>. IN
TXT "path:c3056fb73aa623..." |
>>
|<--------------------------------------------------------------------|
>> ```
>>
>> :question: What encoding should we use for the blinded path
option? Bech32m with the `lnp` prefix?
>>
>> :warning: Alice should query that DNS record using
[DoH](https://datatracker.ietf.org/doc/html/rfc8484) for privacy.
>> She should also query multiple DoH servers to protect from
malicious ones.
>>
>> :warning: Alice should check the AD flag is correctly set (DNSSEC).
>>
>> ### Obtain a Bolt 12 offer from the recipient
>>
>> Now that Alice has a way to reach the node that owns Bob's
domain, she needs to contact them to obtain a Bolt 12 offer from Bob.
>> We use an `onion_message` for that, which has the following
benefits:
>>
>> * Alice doesn't reveal her identity (IP address or `node_id`)
to Bob or Bob's domain
>> * Alice doesn't reveal Bob's identity (IP address or `node_id`)
to her LSP
>> * Alice doesn't even need to know the IP address for Bob's
domain's lightning node
>>
>> ```text
>> Alice Alice's LSP
Bob's LSP Bob
>> | |
| |
>> | onion_message |
| |
>> |-------------------------------->| onion_message
| |
>> | | get_offer_from
=b...@domain.com | |
>> | |---------------------------------->| |
>> | |
| wake_up |
>> | |
|-------------------------------->|
>> | |
| offer |
>> | |
|<--------------------------------|
>> | | onion_message
| |
>> | |<----------------------------------| |
>> | onion_message |
| |
>> | bob's bolt12 offer |
| |
>> | bob's LSP signature |
| |
>> |<--------------------------------|
| |
>> ```
>>
>> Note that Alice cannot verify that the offer she receives is
really from Bob: she has to TOFU (trust on first use).
>> But that's something we fundamentally cannot fix if the only
information Alice has is `b...@domain.com`.
>> However, Alice obtains a signed statement from Bob's LSP that
attests that `b...@domain.com` is associated with the Bolt12 offer
she receives.
>> If she later discovers that this was invalid, she can publish
that proof to show the world that Bob's LSP is malicious.
>>
>> Otherwise, since there needs to be some out-of-band
communication where the recipient advertizes their lightning
address (e.g. on social media), some kind of verification code
could be attached (hash of the `node_id`?).
>> The sender's wallet could optionally add a manual verification
step of that verification code.
>> This would only need to be done once, since Alice can then
reuse the same offer to fetch new invoices.
>>
>> ### Advantages and drawbacks
>>
>> The main advantage of this proposal is that it is simple,
inexpensive and relies on standard mechanisms.
>> Its drawback is that domain owners need to be able to publish
DNS `TXT` records, but that is widely supported.
>>
>> ## Option 2: use `node_announcement` to link nodes to specific
domains
>>
>> This proposal is only based on the lightning network, without
any dependency on DNS or HTTP stacks (apart from certificate
validation).
>>
>> ### Obtain the `node_id` associated with a domain
>>
>> We add fields to `node_announcement` to let nodes advertize
which domains they own.
>> Those fields would typically contain a signature of the
`node_id` using the private key for the corresponding domain TLS
certificate, along with its certificate chain.
>> Alice can then simply sync `node_announcement`s that contain
domain links with her LSP:
>>
>> ```text
>> Alice LSP
>> | |
>> | node_announcement(foobar.com
<http://foobar.com> <http://foobar.com>) |
>> |<-----------------------------------------------|
>> | node_announcement(domain.xyz
<http://domain.xyz> <http://domain.xyz>) |
>> |<-----------------------------------------------|
>> | node_announcement(ln.stuff) |
>> |<-----------------------------------------------|
>> | ... |
>> |<-----------------------------------------------|
>> ```
>>
>> ### Obtain a Bolt 12 offer from the recipient
>>
>> This uses exactly the same onion message mechanism as the
previous proposal.
>>
>> ### Advantages and drawbacks
>>
>> The main advantage of this proposal is that it relies entirely
on lightning protocol messages.
>> Its drawback is that Alice needs to sync some
`node_announcement`s to obtain the domain owner's `node_id`.
>> Alice also needs to validate the certificate chain, which is
old school annoying crypto.
>> It also doesn't allow domain owners to keep their `node_id`
private (which may be useful for small community-based nodes).
>>
>> ## Option 3: use DNS records to directly store Bolt 12 offers
>>
>> Another option would be to make domain owners create one DNS
`TXT` record for each of their user, directly containing their
Bolt 12 offer:
>>
>> | hostname | record type | value |
TTL |
>>
|----------------------------|-------------|---------------------|--------------|
>> | bob._lnaddress.domain.com <http://lnaddress.domain.com>
<http://lnaddress.domain.com>. | TXT | lno1qqx2n6mw2fh2...
| offer expiry |
>>
>> ```text
>> Alice DNS server
>> | |
>> | dig TXT bob._lnaddress.domain.com
<http://lnaddress.domain.com> <http://lnaddress.domain.com>
|
>>
|-------------------------------------------------------------------->|
>> | bob._lnaddress.domain.com
<http://lnaddress.domain.com> <http://lnaddress.domain.com>. IN
TXT "lno1qqx2n6mw2fh2..." |
>>
|<--------------------------------------------------------------------|
>> ```
>>
>> :warning: Alice should query that DNS record using
[DoH](https://datatracker.ietf.org/doc/html/rfc8484) for privacy.
>> She should also query multiple DoH servers to protect from
malicious ones.
>>
>> :warning: Alice should check the AD flag is correctly set (DNSSEC).
>>
>> ### Advantages and drawbacks
>>
>> The main advantage of this proposal is that it is
straightforward for the sender and doesn't require any addition to
the lightning protocol.
>>
>> There are some drawbacks though, mostly for the domain owner,
because they will need to create a lot of DNS records (one per user).
>> If they're using a cloud provider, there will be limitations in
the number of records they are allowed to create.
>> They may not have programmatic access to perform that operation
automatically (when a user creates their lightning address).
>> Cheers,
>> Bastien
>>
>>
>> _______________________________________________
>> Lightning-dev mailing list
>> Lightning-dev@lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev
>
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