There is a discussion about clarifying how BIP70 signs payment requests here:

The issue is what to do with the signature field before signing. The code Mike and I initially wrote does this:


(sets signature to the empty string)

I think that is a mistake; it should be:


(clears signature field, so it is not serialized at all).

So: if you are implementing, or have implemented, the payment protocol, please chime in. I'd like to change the spec and the reference implementation NOW, while BIP70 is still a 'Draft'.

Because this type of "hey, I'm implementing your standard and it doesn't work the way I think it should" mistake is exactly why BIPs take a while before being declared 'Final.'

Gavin Andresen