From: ZmnSCPxj <ZmnSCPxj@protonmail•com>
To: AdamISZ <AdamISZ@protonmail•com>,
Bitcoin Protocol Discussion
<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] LN & Coinjoin, a Great Tx Format Wedding
Date: Sun, 23 Feb 2020 00:59:46 +0000 [thread overview]
Message-ID: <x7A06kB4r0DzPTeDDWWouWLXT5_5YRaHax76XP_ToY0aUAPHXVt8Wuvf3RRpFpguIFD53Ho_KQM4WYEkFl6ZZlVw6KIk-GP5izmGDVppfvA=@protonmail.com> (raw)
In-Reply-To: <L95umnyb-GwoyP_ZWM7oNmMbhooYpCFXoKAGRPoPOpGpMGhMHQWuczKhJ2VX2nrZt3jaJ5bOMy5dvQ3DYqs_O_eEsA_63dd2_rvdoOzoGoI=@protonmail.com>
Good morning waxwing,
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Friday, 21 February 2020 22:17, Antoine Riard via bitcoin-dev bitcoin-dev@lists•linuxfoundation.org wrote:
>
> > How can a Bitcoin tranaction leak protocol usage ?
> >
> > - the output type (p2sh, p2wsh, ...)
> > - the spending policy (2-of-3 multisig, timelock, hashlock,...)
> > - outputs ordering (BIP69)
> > - nLocktime/nSequence
> > - RBF-signaling
> > - Equal-value outputs
> > - weird watermark (LN commitment tx obfuscated commitment number)
> > - fees strategy like CPFP
> > - in-protocol announcements [0]
>
> Good list.
> Another one, usually wouldn't be protocol as much as wallet leakage, but could be: utxo selection algorithm (which of course may be difficult to deduce, but often, far from impossible).
> (Also trivial and increasingly irrelevant, but nVersion).
>
> With regards to coinjoin in this context (I know your points are much broader), my comment is:
> For existing protocols (joinmarket's, wasabi's, samourai's), in the equal-outs paradigm, I don't see much that can be done in this area.
> But I would ask people to consider CoinJoinXT[1] more seriously in a taproot/schnorr world, since it addresses this exact point. With a short (not cross-block like swaps or LN setup) interaction, participants can arrange the effect of coinjoin without the on-chain watermark of coinjoin (so, steganographic). The taproot/schnorr part is needed there because multisig is required from transaction to transaction in that protocol, so doing it today is less interesting (albeit still interesting).
CoinJoinXT is indeed something I am interested in at some point: https://zmnscpxj.github.io/bitcoin/coinjoinxt.html
The above writeup is a client-server model, with multiple clients mixing.
If none of the participants reveal that a CoinJoinXT was done, then the graph is difficult to detect as such.
However, if any participants reveal that a CoinJoinXT was done, it has a fallback such that it is almost as good as an equal-value CoinJoin (but takes up more block space).
At least it is not immediately obvious that it is in fact a CoinJoinXT from *just* a simple transaction analysis, which we hope is enough to deter simple policies like "check N transactions back for a transaction with more than one equal-valued output".
Regards,
ZmnSCPxj
next prev parent reply other threads:[~2020-02-23 0:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 22:17 Antoine Riard
2020-02-22 12:10 ` AdamISZ
2020-02-23 0:59 ` ZmnSCPxj [this message]
2020-02-24 17:58 ` Antoine Riard
2020-02-23 1:29 ` ZmnSCPxj
2020-02-24 18:26 ` Antoine Riard
2020-02-24 23:35 ` ZmnSCPxj
2020-02-25 19:16 ` Antoine Riard
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