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From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
To: Anthony Towns <aj@erisian.com.au>
Cc: "bitcoin-dev@lists.linuxfoundation.org"
	<bitcoin-dev@lists.linuxfoundation.org>,
	"lightning-dev@lists.linuxfoundation.org"
	<lightning-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] [Lightning-dev] More thoughts on NOINPUT safety
Date: Thu, 21 Mar 2019 10:05:09 +0000	[thread overview]
Message-ID: <5v4CPrMXyoMw0i1WtYYuIa_rMgkpq5NpnDhTNqTTZtfKKnFtwrbEGJnTD8ul71EM-MNpuo1R4znv4tPpwwm3Ys3m2Dbm3xsOGi96NYE9qfU=@protonmail.com> (raw)
In-Reply-To: <20190321090614.7ir64g2ehn3pz2cb@erisian.com.au>

Good morning aj,

> > Then each update transaction pays out to:
> > OP_IF
> > <csv_delta> OP_CSV OP_DROP
> > <muSig(A_si,B_si)> OP_CHECKSIGVERIFY <Q> OP_CHECKSIG
> > OP_ELSE
> > <i> OP_CHECKLOCKTIMEVERIFY OP_DROP
> > <muSig(A_u,B_u)> OP_CHECKSIGVERIFY <Q> OP_CHECKSIG
> > OP_ENDIF
>
> Yeah.
>
> I think we could potentially make that shorter still:
>
> IF OP_CODESEPARATOR <i> OP_CHECKLOCKTIMEVERIFY OP_DROP ENDIF
> <muSig(A_u,B_u)> OP_CHECKDLSVERIFY <Q> OP_CHECKDLS
>
> Signing with NOINPUT,NOSCRIPT and codeseparatorpos=1 enforces CLTV
> and allows binding to any prior update tx -- so works for an update tx
> spending previous update txs; while signing with codeseparatorpos=-1
> and NOINPUT but committing to the script code and nSequence (for the
> CSV delay) allows binding to only that update tx -- so works for the
> settlement tx. That's two pubkeys, two sigs, and the taproot point
> reveal.


Actually, the shared keys are different in the two branches above.
The "update" branch (which has no `OP_CSV`) uses the same constant `A_u` and `B_u` points.
The "state commit" branch (which has `OP_CSV`) uses different `A_si` and `B_si` points depending on `i` (state/sequence number).

Also, I cannot understand `OP_CODESEPARATOR`, please no.

Regards,
ZmnSCPxj


  reply	other threads:[~2019-03-21 10:05 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-13  1:41 [bitcoin-dev] More thoughts on NOINPUT safety Anthony Towns
2019-03-13  6:41 ` [bitcoin-dev] [Lightning-dev] " ZmnSCPxj
2019-03-13 11:10   ` Anthony Towns
2019-03-14  5:22     ` ZmnSCPxj
2019-03-14  7:24       ` Anthony Towns
2019-03-14  7:55         ` ZmnSCPxj
2019-03-14 12:00         ` Christian Decker
2019-03-20  0:22 ` Rusty Russell
2019-03-20  3:33   ` Rusty Russell
2019-03-20  7:38     ` ZmnSCPxj
2019-03-20  8:07       ` ZmnSCPxj
2019-03-21  8:37         ` Johnson Lau
2019-03-21  9:06         ` Anthony Towns
2019-03-21 10:05           ` ZmnSCPxj [this message]
2019-03-21 11:55             ` Anthony Towns
2019-03-22  1:59               ` ZmnSCPxj
2019-03-22  2:58                 ` Anthony Towns
2019-03-22  7:46                   ` ZmnSCPxj
2019-03-22  4:23                 ` Johnson Lau

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