[hashcash] Re: stamp creation std. deviation
- From: Adam Back <adam@xxxxxxxxxxxxxxx>
- To: hashcash@xxxxxxxxxxxxx
- Date: Fri, 13 Aug 2004 11:42:34 -0400
Oh I see! And this implies as you would just use a "19-bit" type B in
place of a "20-bit" type A, as it would cost 2x as much they are
exactly equivalent with regards to cost & variance. QED.
Adam
On Fri, Aug 13, 2004 at 03:25:23PM +0000, Justin wrote:
> On 2004-08-13T09:07:44-0400, Adam Back wrote:
> > Yes. It's just the 21st bit of a 20 bit stamp with type B would
> > _have_ to be 1 whereas now (type A) it can be either 0 or 1.
>
> Yes, but I think you miss my meaning.
>
> The new scheme (B) is indistinguishable computationally (or wrt entropy
> or probability distributions) from a 21-bit stamp.
>
> You don't gain any advantage. You could specify any pattern you wanted
> for collisions. For a 20-bit stamp, some could be:
>
> 01010101010101010101
> 10101010101010101010
> 00000000000000000000 (current)
> 00010000000100000001
>
> What you propose is
>
> 000000000000000000001, which is a 21 bit pattern, therefore it is the
> equivalent of a 21-bit stamp under the current validation scheme.
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