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Date: Mon, 2 Jan 2012 11:42:31 -0500 (EST)
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To: Gavin Andresen <gavinandresen@gmail.com>
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Cc: bitcoin-development@lists.sourceforge.net
Subject: Re: [Bitcoin-development] Alternative to OP_EVAL
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Seems ... acceptable from first glance.

Though I propose an ammendent to either

(1)

make the script: OP_NOP1 HASH160 <push-20-byte-hash> EQUAL to make it 
extremely easy to see from the first byte that this is verly likely to be 
a special transaction (or more accurately if the first byte isn't 
OP_NOP1 then you immediately know it isn't a special script and can even 
disregard the token).

or

(2)

If you are feel like spending another byte make the script:
OP_NOP1 <push-special-script-version-number> <special-script>

and assign 1 to this special script, making this case:

OP_NOP1 OP_1 HASH160 <push-20-byte-hash> EQUAL

On Mon, 2 Jan 2012, Gavin Andresen wrote:

> Here are my latest thoughts on a safer OP_EVAL alternative, inspired
> by all the ideas and agitated IRC and email
> discussions of the last week or so:
>
> Goal:  Let users publish a short "funding address" that is the hash of
> an arbitrary redemption Script revealed when they spend the funds,
> implemented in a backwards-compatible-in-the-blockchain way.
>
> Proposal:
>
> A new 'standard' transaction type, "pay to Script hash":
>
> scriptPubKey:  HASH160 <push-20-byte-hash>  EQUAL
>
> Redeemed with the same scriptSig as the OP_EVAL proposal:
> <signatures> <serialized Script>
>
> Old clients/miners will ignore <signatures> and just validate that the
> hash of <serialized Script> matches.
>
> New clients/miners will recognize the new type of transaction and will
> do the following additional validation:
>
> 1. Fail validation if there were any operations other than "push data"
> in the original scriptSig.
> 2. Deserialize the top (last) item on the scriptSig stack (fail
> validation if it fails to deserialize properly).
> 3. Run an additional validation on the deserialized script, using the
> remaining items on the scriptSig stack and the deserialized script as
> the scriptPubKey.
>
>
> ---------------
>
> As Amir said in IRC chat today, "the idea is a hack.... but I like it."
>
> I like it, too-- it is cleaner than OP_EVAL, more straightforward to
> implement, and pretty much exactly matches the feature I care about
> (moving code from the scriptPubKey to the scriptSig). There are no
> special cases like "CODESEPARATORS not allowed in <serialized
> script>".
>
>

-- 
Russell O'Connor                                      <http://r6.ca/>
``All talk about `theft,''' the general counsel of the American Graphophone
Company wrote, ``is the merest claptrap, for there exists no property in
ideas musical, literary or artistic, except as defined by statute.''