public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
From: Tom Trevethan <tom@commerceblock.com>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: [bitcoin-dev] Fwd:  Blinded 2-party Musig2
Date: Thu, 27 Jul 2023 14:25:33 +0100	[thread overview]
Message-ID: <CAJvkSsea+aKJFkNpNxHPAGCxrYwU+8wXOzV-8yH=qacGta++ig@mail.gmail.com> (raw)
In-Reply-To: <CAJvkSsfa8rzbwXiatZBpwQ6d4d94yLQifK8gyq3k-rq_1SH4OQ@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 1441 bytes --]

@Jonas

OK, thanks, I get the logic now. I believe this attack can be mitigated (at
least in the case of using this scheme for statechains) by the receiver of
a coin verifying the construction of all previous challenges.

So in this case, the sender of a coin would record R2[K-1] in addition to m
(and any c blinding nonce used) for the signature it generates with the
server. It would then send this (and all previous R2 values i = 0, ...,
K-2) to the receiver.

The receiver would then query the server for the full set (i = 0, ..., K-1)
of R1[i] values it has generated, and the corresponding (blinded) c[i]
values used for each co-signing it has performed on this key. The
receiver would then verify that each previous c[i] (i = 0, ... K-1) has
been correctly formed and includes the server generated R1[i].

If any of the c values fail to verify against the values of R1 provided by
the server, then the coin is invalid.

On Thu, Jul 27, 2023 at 9:08 AM Jonas Nick <jonasdnick@gmail.com> wrote:

> No, proof of knowledge of the r values used to generate each R does not
> prevent
> Wagner's attack. I wrote
>
>  >   Using Wagner's algorithm, choose R2[0], ..., R2[K-1] such that
>  >    c[0] + ... + c[K-1] = c[K].
>
> You can think of this as actually choosing scalars r2[0], ..., r2[K-1] and
> define R2[i] = r2[i]*G. The attacker chooses r2[i]. The attack wouldn't
> make
> sense if he didn't.
>

[-- Attachment #2: Type: text/html, Size: 2040 bytes --]

  parent reply	other threads:[~2023-07-27 13:25 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-24  7:46 [bitcoin-dev] Blinded 2-party Musig2 Tom Trevethan
2023-07-24 10:50 ` ZmnSCPxj
2023-07-24 14:25   ` Erik Aronesty
2023-07-24 16:08     ` Tom Trevethan
2023-07-24 15:57   ` Tom Trevethan
2023-07-24 14:12 ` Jonas Nick
2023-07-24 14:40   ` Erik Aronesty
2023-07-24 15:40     ` Jonas Nick
2023-07-24 16:51   ` AdamISZ
2023-07-25 14:12     ` Erik Aronesty
2023-07-25 16:05       ` Tom Trevethan
2023-07-26  4:09         ` Erik Aronesty
2023-07-26 17:40           ` Andrew Poelstra
2023-07-26 19:59           ` Jonas Nick
2023-07-26 20:35             ` Tom Trevethan
2023-07-26 22:06               ` Erik Aronesty
2023-07-27  2:54                 ` Lloyd Fournier
2023-07-27  8:07               ` Jonas Nick
     [not found]                 ` <CAJvkSsfa8rzbwXiatZBpwQ6d4d94yLQifK8gyq3k-rq_1SH4OQ@mail.gmail.com>
2023-07-27 13:25                   ` Tom Trevethan [this message]
2023-08-07  0:55                     ` Tom Trevethan
2023-08-08 17:44                       ` moonsettler
2023-08-09 15:14                         ` Tom Trevethan
2023-08-10  3:30                           ` Lloyd Fournier
2023-08-10 11:59                             ` Tom Trevethan
2023-08-14  6:31                               ` Lloyd Fournier
2023-08-30 10:52                       ` Tom Trevethan
2023-07-24 15:39 ` Jonas Nick
2023-07-24 16:22   ` Tom Trevethan
2023-07-26  9:44   ` moonsettler
2023-07-26 14:59     ` Jonas Nick
2023-07-26 19:19     ` AdamISZ
2023-07-26 19:28       ` moonsettler
2023-07-27  5:51         ` AdamISZ

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAJvkSsea+aKJFkNpNxHPAGCxrYwU+8wXOzV-8yH=qacGta++ig@mail.gmail.com' \
    --to=tom@commerceblock.com \
    --cc=bitcoin-dev@lists.linuxfoundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox