[hashcash] Re: status of hashcash version 1?

  • From: Ben Laurie <ben@xxxxxxxxxxxxx>
  • To: hashcash@xxxxxxxxxxxxx
  • Date: Sun, 22 Aug 2004 11:50:02 +0100

Adam Back wrote:

Well I put up some source that implements one proposed version 1
format here:

        http://www.hashcash.org/source/current/

it does not come with multiple sub-puzzle support which could be added.

The other part missing from the implementation is the hooks to make
use of extensions.  ie I was thinking for extension a (syntax

X-Hashcash: 1:20:040430:kyle@xxxxxxxxxxx:mac-key=0123456789abcdef01234
        56789abcdef:35385ea2086e2b12:15003

then this would be invoked as:

        hashcash-ext-mac-key 0123456789abcdef0123456789abcdef $stamp

where $stamp would be the full stamp also.  So if the extension was
missing it would be ignored.  If the extension handler program returns
failure the stamp would be rejected, and if the extension handler
program returns success the stamp would be accepted (if it was
otherwise valid).

Plus need to integrate Chromatix fast hashcash code.  Think main issue
there is to have a way to know which code to run on a machine based on
eg some CPU properties code so it is fast, or a very short trial of
the set of alternatives that run on the CPU to measure which is best.


And the last and probably biggest issue is how to deal with CPU inflation. I was thinking this could be implemented using the extension mechanism. One way is to pass around p2p the largest required-hash definition seen so far, and have someone / some group changing this over time using some pre-agreed criteria.

Benchmark your own CPU, then accept cash for anything that takes more than n seconds on your CPU. Generate cash that takes n*k seconds. This naturally evolves to take account of improved speeds _and_ variance without tweaking being required after setting an initial value (though the owner of a very fast CPU might have to downgrade the default n, and a very slow CPU upgrade k).


Cheers,

Ben.

--
http://www.apache-ssl.org/ben.html       http://www.thebunker.net/

"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff

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