Date: Mon, 8 Aug 2016 17:46:33 -0700
From: Peter Todd <pete@petertodd.org>
To: Luke Dashjr <luke@dashjr.org>
Message-ID: <20160809004633.GA1653@fedora-21-dvm>
References: <CAKazn3mKUMMz0wyqTsgbkd4mBLgvG2PXziXhgRTi4hX_ApbPhg@mail.gmail.com>
	<20160720054654.GA1420@fedora-21-dvm>
	<201607200617.40917.luke@dashjr.org>
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In-Reply-To: <201607200617.40917.luke@dashjr.org>
User-Agent: Mutt/1.5.23 (2014-03-12)
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] BIP draft: HTLC transactions
Precedence: list


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On Wed, Jul 20, 2016 at 06:17:39AM +0000, Luke Dashjr wrote:
> On Wednesday, July 20, 2016 5:46:54 AM Peter Todd via bitcoin-dev wrote:
> > On Tue, Jul 19, 2016 at 10:35:39PM -0600, Sean Bowe via bitcoin-dev wro=
te:
> > > I'm requesting feedback for Hash Time-Locked Contract (HTLC) transact=
ions
> > > in Bitcoin.
> > >=20
> > > HTLC transactions allow you to pay for the preimage of a hash. CSV/CL=
TV
> > > can be used to recover your funds if the other party is not cooperati=
ve.
> > > These
> > >=20
> > > scripts take the following general form:
> > >     [HASHOP] <digest> OP_EQUAL
> > >     OP_IF
> > >    =20
> > >         <seller pubkey>
> > >    =20
> > >     OP_ELSE
> > >    =20
> > >         <num> [TIMEOUTOP] OP_DROP <buyer pubkey>
> > >    =20
> > >     OP_ENDIF
> > >     OP_CHECKSIG
> >=20
> > Note that because you're hashing the top item on the stack regardless
> > scriptSig's that satisfy HTLC's are malleable: that top stack item can =
be
> > changed anything in the digest-not-provided case and the script still
> > passes.
>=20
> OP_SIZE
> OP_IF
>   [HASHOP] <digest> OP_EQUALVERIFY
>   <seller pubkey>
> OP_ELSE
>   <num> [TIMEOUTOP]
>   <buyer pubkey>
> OP_ENDIF
> OP_CHECKSIG

Ha! That's brilliant; good job.

--=20
https://petertodd.org 'peter'[:-1]@petertodd.org

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