From: ZmnSCPxj <ZmnSCPxj@protonmail•com>
To: Anthony Towns <aj@erisian•com.au>,
Bitcoin Protocol Discussion
<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 118 and SIGHASH_ANYPREVOUT
Date: Fri, 10 Jul 2020 03:29:39 +0000 [thread overview]
Message-ID: <O_Zr7tM2TYwJdFS0o9RraXrtRPI4ZcVU65qcBpg-tvTPOqnGWkEUDQY5XqcihbUyAHF31L4isFWsD_u2SsSb8YzfjYDWiVXQsr6oAd9YXBY=@protonmail.com> (raw)
In-Reply-To: <20200709214048.27mycsi5h2bnv3cc@erisian.com.au>
Good morning aj,
It seems okay to me.
--
Slightly off-topic, but I suppose a Decker-Russell-Osuntokun construction could, in theory, have only a single internal taproot pubkey, `P = MuSig(A, B)` for a channel between A and B.
So the funding outpoint would be spent with a taprooted P + a single tapscript `<1> OP_CHECKSIG`.
Update transactions would be signed with the internal taproot pubkey using `SIGHASH_ANYPREVOUTANYSCRIPT`.
The update transaction output would be spendable with a taprooted P + a single tapscript `<index + 1> OP_CHECKLOCKTIMEVERIFY OP_DROP <1> OP_CHECKSIG`.
Each update transaction would have a monotonically-increasing `nLockTime`, i.e. the above `index`.
Then a state transaction would be signed with the internal taproot pubkey using `SIGHASH_ANYPREVOUT`, which commits to the exact script including `<index + 1>`, which is unique for each update transaction.
Thus a state transaction can only spend the specific update transaction, but the update transaction can spend the funding outpoint or any update transaction outpoint.
State transaction input would have an `nSequence` requiring a relative locktime of the agreed-upon unilateral close delay.
The above assumes MuSig signing, which requires 1.5 round trips for a channel, or three broadcast rounds for a multiparticipant (n >= 3) construction.
Regards,
ZmnSCPxj
> Hello world,
>
> After talking with Christina ages ago, we came to the conclusion that
> it made more sense to update BIP 118 to the latest thinking than have
> a new BIP number, so I've (finally) opened a (draft) PR to update BIP
> 118 with the ANYPREVOUT bip I've passed around to a few people,
>
> https://github.com/bitcoin/bips/pull/943
>
> Probably easiest to just read the new BIP text on github:
>
> https://github.com/ajtowns/bips/blob/bip-anyprevout/bip-0118.mediawiki
>
> It doesn't come with tested code at this point, but I figure better to
> have the text available for discussion than nothing.
>
> Some significant changes since previous discussion include complete lack
> of chaperone signatures or anything like it (if you want them, you can
> always add them yourself, of course), and that ANYPREVOUTANYSCRIPT no
> longer commits to the value (details/rationale in the text).
>
> Cheers,
> aj
>
> bitcoin-dev mailing list
> bitcoin-dev@lists•linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
next prev parent reply other threads:[~2020-07-10 3:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-09 21:40 Anthony Towns
2020-07-09 22:30 ` Anthony Towns
2020-07-10 7:46 ` Christian Decker
2020-07-10 3:29 ` ZmnSCPxj [this message]
2020-08-03 19:27 ` Richard Myers
2020-08-04 1:38 ` ZmnSCPxj
2020-08-04 4:02 ` lf-lists
2020-08-04 4:23 ` ZmnSCPxj
2020-08-04 10:38 ` Christian Decker
2020-08-04 13:10 ` Matt Corallo
2020-08-04 14:59 ` ZmnSCPxj
2020-08-06 15:58 ` Matt Corallo
2020-08-07 15:34 ` Richard Myers
2020-08-11 0:14 ` Matt Corallo
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