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 wrote:
> > > I'm requesting feedback for Hash Time-Locked Contract (HTLC) transactions
> > > in Bitcoin.
> > > 
> > > HTLC transactions allow you to pay for the preimage of a hash. CSV/CLTV
> > > can be used to recover your funds if the other party is not cooperative.
> > > These
> > > 
> > > scripts take the following general form:
> > >     [HASHOP] <digest> OP_EQUAL
> > >     OP_IF
> > >     
> > >         <seller pubkey>
> > >     
> > >     OP_ELSE
> > >     
> > >         <num> [TIMEOUTOP] OP_DROP <buyer pubkey>
> > >     
> > >     OP_ENDIF
> > >     OP_CHECKSIG
> > 
> > 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.
> 
> 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.

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