From: "Luke-Jr" <luke@dashjr.org>
To: bitcoin-development@lists.sourceforge.net
Date: Fri, 25 Apr 2014 19:18:43 +0000
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Subject: Re: [Bitcoin-development] BIP - Hash Locked Transaction
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This one looks entirely useless (it cannot be made secure), and the assertion 
that it is necessary for atomic cross-chain transfers seems unfounded and 
probably wrong...

Luke

On Friday, April 25, 2014 6:49:37 PM Tier Nolan wrote:
> As part of the atomic cross chain system, outputs need to be hash locked.
> 
> https://github.com/TierNolan/bips/blob/bip4x/bip-0045.mediawiki
> 
> https://bitcointalk.org/index.php?topic=193281.msg2224949#msg2224949
> 
> A user needs to provide x corresponding to hash(x) in order to spend an
> output.
> 
> Under the protocol, one of the participants is required to provide the
> secret number in order to spend an output.  Once they do that, the other
> participant can use the secret number to spend an output on the other
> chain.  This provides a mechanism to link the 2 chains together (in
> addition to lock times).  Once the first output is spent, that commits the
> transfer.
> 
> This is half of the scripting operations required to implement the
> protocol.
> 
> The proposal is to make this an adder on to the other standard
> transactions.  It does a check that the hash matches, and then runs the
> standard transaction as normal.
> 
> Adding the prefix to a P2SH transactions wouldn't work, since the template
> wouldn't match.
> 
> A script of this form could be embedded into a P2SH output.
> 
> I think that is ok, since embedding the "password" in the hashed script
> gets all the benefits.
> 
> If there is agreement, I can code up the reference implementation as a PR.