[hashcash] Re: hashcash v1 questions
- From: Adam Back <adam@xxxxxxxxxxxxxxx>
- To: hashcash@xxxxxxxxxxxxx
- Date: Tue, 1 Jun 2004 03:39:51 -0400
On Tue, Jun 01, 2004 at 03:00:47AM -0400, Hubert Chan wrote:
> >>>>> "Justin" == Justin <justin-hashcash@xxxxxxxx> writes:
> Justin> Can't the counter be abused by starting it at an arbitrary
> Justin> value? If it's used for filtering, inflating the counter gives
> Justin> the sender an advantage.
>
> I think that the counter is only meaningful to the recipient as
> "interesting statistics", and isn't supposed to have any practical
> purpose on the receiving end. But I guess Adam would know more about
> that.
Correct. We need something that can work through lots of values. A
counter is a simple way to do that. The receipient can't rely on the
sender counting in order. We've seen this already with Jonathan
re-using the counter as a padding mechanism to start with a large
counter that is just before SHA1 boundary.
And all the recipient cares is that the msg hashes to desired number
of leading 0 bits.
Adam
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