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Cc: bitcoin-development <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] BIP: Voluntary deposit bonds
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On Mon, Dec 29, 2014 at 7:21 PM, Sergio Lerner
<sergiolerner@certimix.com> wrote:
> I propose to allow miners to voluntarily lock funds by letting miners
> add additional inputs to the coinbase transaction. Currently the
> coinbase transaction does not allow any real input  to be added (only a
> pseudo-input).
> This is a hard-fork, and we could include it the next time a hardfork is
> made.
> The modifications to the code are minimal (no more than 12 lines
> modified where IsCoinBase() is called), and they generally involve
> removing code, not adding.


If the motivation is purely enabling different rules in a soft-fork
than I think nothing needs to be done.

Instead of providing inputs to a coinbase: you provide an unusual
anyone can spend transaction in the block which pays to fees; and
simultaneously add a soft-forking rule that makes that anyone can
spend rule no longer anyone can spend.

To make that more concrete.  E.g. You make your anyone can spend
output   "PUSH<hash of coinbase output script_pubkeys> OP_NOP3".  Now
this anyone can pay transaction is really just a coinbase input.

The construction is reasonably efficient, and also more flexible-- in
that it could control the data under the hash in more flexible ways
than available in the existing sighash flags.


As an aside, I'm not sure that I agree with the claim that making
coinbases have inputs is a simple modification... as we use one of the
inputs already as the special coinbase field and at least that must be
special cased.