On Wed, Mar 12, 2014 at 05:14:25PM +0100, Mike Hearn wrote:
> >
> > Can this be calculated in advance knowing the initial transaction size and
> > the number of signatures required?
> >
> 
> Sure of course. You assume each signature to be placed in the tx is 73
> bytes. Not very hard, but if the tx you get back from the API doesn't
> contain such a 73-byte sentinel value then it's harder to be sure that this
> part was done correctly.

Multisig signing is an example of untrusted input from an adversary;
this is a good example where you'd be better off just handling it
correctly rather than trying to "make it easier". (although handling it
correctly may include internally converting every not-yet-signed dummy
signature into a 73 bytes pushdata prior to calculating the size)

-- 
'peter'[:-1]@petertodd.org
0000000000000000e18643801741dc70db6fda175230012b0f697024218cd9ef