Add p2ms as a recognized standard script type.

[wardlem]

No description provided.

[wardlem]

This PR requires a consideration of what a templating ASM syntax should look like. Currently, it looks like OP_HASH160 <20-byte-script-hash> OP_EQUAL. The template processor sees that the script begins with 20-byte and enforces that the push_data value is 20 bytes. This works ok, though it isn't perfect. The templating language currently doesn't support opcode parameters, which are required in a p2ms template (for m and n). For this, I was considering <OP_1-OP_16> and it would see that it expects an op within that range. The public keys also need to be repeated, and this needs a syntax. I was considering, for the public keys <33-byte-public-key...> where the ... indicates repetition.

I am not sold on any of these choices.

[JBaczuk]

Can you explain how this would be used/exposed? Or maybe what you mean by templating syntax. I'm trying to figure out when I would want to type <20-byte-script-hash> instead of the actual hash.

[wardlem]

Can you explain how this would be used/exposed? Or maybe what you mean by templating syntax. I'm trying to figure out when I would want to type <20-byte-script-hash> instead of the actual hash.

Yes. Script types are recognized using special "template" scripts that have placeholder values where variable data is used in standard scripts. For example, the template: OP_HASH160 <20-byte-script-hash> OP_EQUAL will match the script OP_HASH160 52973f3519d5d248004767efb874aa2a3b2b37ce OP_EQUAL which allows the script to be detected as a p2sh pubKey script. You can see how this is implemented in the templates.js file. This functionality is not currently directly exposed to the end user as a top-level export, though it could be in the future.

[JBaczuk]

Ok I get what your talking about. So for the p2ms why not just use a template like:

<p2ms>

Then the template processor knows to look for an OP_M which must be 0-16, then it looks for the last byte to be OP_N from 0-16, and finally after the OP_M, there must be N compressed pubkeys (always 33 bytes). I'm not positive, but I don't think uncompressed keys are valid in a standard p2ms, but we should verify this.

Another alternative (which might be more descriptive if this template was ever exposed to the user):

<OP_M> <pubkey> ... <OP_N>

Though this seems to make more work for the template processor.

[wardlem]

Another alternative (which might be more descriptive if this template was ever exposed to the user):

<OP_M> <pubkey> ... <OP_N>

Though this seems to make more work for the template processor.

It is a little more work for the template processor, but I believe that this is a natural way to describe what a p2ms looks like. I vote for this.