On Tue, Dec 03, 2013 at 11:40:35AM +1000, Gavin Andresen wrote:
> On Tue, Dec 3, 2013 at 12:44 AM, Mike Hearn <mike@plan99.net> wrote:
> 
> > PPv1 doesn't have any notion of fee unfortunately. I suppose it could be
> > added easily, but we also need to launch the existing feature set.
> >
> 
> Lets bang out a merchant-pays-fee extension.
> 
> How about:
> 
> SPEC:
> 
>     optional uint64 allowfee    tag number=1000
> 
> Allow up to allowfee satoshis to be deducted from the amount paid to be
> used to pay Bitcoin network transaction fees. A wallet implementation must
> not reduce the amount paid for fees more than allowfee, and transaction
> fees must be equal to or greater than the amount reduced.

Fees are per byte of tx data; call it allowfeeperkb, and given that fees
are required - the merchant would really rather not waste up to about
twice as much on fees for a child-pays-for-parent - it should be called
requirefeeperkb.

Back to your point, the merchant wants to limit total fees that have
been deducted - 'allowfee' is still a good idea - but only in
conjunction with specifying fee-per-kb requirements.

UI once both are implemented is to not show anything in the default
case, and explain to the user why they have to pay extra in the unusual
case where they are spending a whole bunch of dust.

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