>
> I hear that. But I don't see why mainstream wallets and wallets
> designed for crypto research should not share a common core.
>

I think there was some misunderstanding. I was saying they *could and
should* share common cores, so we are in agreement without realising it :)
I also didn't mean to imply there was anything special about bitcoinj, just
that it's an example of a wallet engine that's already in use.


> BIP70 is interesting, indeed, although I still fail to understand why
> (according to the specs I saw) the PaymentRequest message is signed,
> but not the Payment message.
>

Because it's intended to be submitted via HTTPS. But what would you sign
the message with? Some arbitrary key bound to the transaction?