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From: Anthony Towns <aj@erisian.com.au>
To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
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: Fri, 22 Mar 2019 12:58:46 +1000	[thread overview]
Message-ID: <20190322025846.ltsqgknp4s7um6lg@erisian.com.au> (raw)
In-Reply-To: <ITq8Tl8XaPXWzqs0F7yY3POHtysci93evnyLteDL9bYRxjjgJbTV_d-xCn_j5AZApGqCIBQ0p6UH8S-bD_n8hm1IMYS98ukpJkO4PGDXsuQ=@protonmail.com>

On Fri, Mar 22, 2019 at 01:59:14AM +0000, ZmnSCPxj wrote:
> > If codeseparator is too scary, you could probably also just always
> > require the locktime (ie for settlmenet txs as well as update txs), ie:
> > OP_CHECKLOCKTIMEVERIFY OP_DROP
> > <muSig(A_u,B_u)> OP_CHECKDLSVERIFY <Q> OP_CHECKDLS
> > and have update txs set their timelock; and settlement txs set a absolute
> > timelock, relative timelock via sequence, and commit to the script code.
> 
> I think the issue I have here is the lack of `OP_CSV` in the settlement branch.

You can enforce the relative timelock in the settlement branch simply
by refusing to sign a settlement tx that doesn't have the timelock set;
the OP_CSV is redundant.

> Consider a channel with offchain transactions update-1, settlement-1, update-2, and settlement-2.
> If update-1 is placed onchain, update-1 is also immediately spendable by settlement-1.

settlement-1 was signed by you, and when you signed it you ensured that
nsequence was set as per BIP-68, and NOINPUT sigs commit to nsequence,
so if anyone changed that after the fact the sig isn't valid. Because
BIP-68 is enforced by consensus, update-1 isn't immediately spendable
by settlement-1.

Cheers,
aj



  reply	other threads:[~2019-03-22  2:58 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
2019-03-21 11:55             ` Anthony Towns
2019-03-22  1:59               ` ZmnSCPxj
2019-03-22  2:58                 ` Anthony Towns [this message]
2019-03-22  7:46                   ` ZmnSCPxj
2019-03-22  4:23                 ` Johnson Lau

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