RPOW - Reusable Proofs of Work

R. A. Hettinga rah at shipwright.com
Sun Aug 15 14:36:51 EDT 2004

--- begin forwarded text

To: cypherpunks at al-qaeda.net
Subject: RPOW - Reusable Proofs of Work
Date: Sun, 15 Aug 2004 10:43:09 -0700 (PDT)
From: hal at finney.org ("Hal Finney")
Sender: owner-cypherpunks at al-qaeda.net

I'd like to invite members of this list to try out my new
hashcash-based server, rpow.net.

This system receives hashcash as a Proof of Work (POW) token, and in
exchange creates RSA-signed tokens which I call Reusable Proof of Work
(RPOW) tokens.  RPOWs can then be transferred from person to person and
exchanged for new RPOWs at each step.  Each RPOW or POW token can only
be used once but since it gives birth to a new one, it is as though the
same token can be handed from person to person.

Because RPOWs are only created from equal-value POWs or RPOWs, they are
as rare and "valuable" as the hashcash that was used to create them.
But they are reusable, unlike hashcash.

The new concept in the server is the security model.  The RPOW server
is running on a high-security processor card, the IBM 4758 Secure
Cryptographic Coprocessor, validated to FIPS-140 level 4.  This card
has the capability to deliver a signed attestation of the software
configuration on the board, which any (sufficiently motivated) user
can verify against the published source code of the system.  This lets
everyone see that the system has no back doors and will only create RPOW
tokens when supplied with POW/RPOW tokens of equal value.

This is what creates trust in RPOWs as actually embodying their claimed
values, the knowledge that they were in fact created based on an equal
value POW (hashcash) token.

I have a lot more information about the system at rpow.net, along with
downloadable source code.  There is also a crude web interface which
lets you exchange POWs for RPOWs without downloading the client.

This system is in early beta right now so I'd appreciate any feedback
if anyone has a chance to try it out.  Please keep in mind that if there
are problems I may need to reload the server code, which will invalidate
any RPOW tokens which people have previously created.  So don't go too
crazy hoarding up RPOWs quite yet.

Thanks very much -

Hal Finney

--- end forwarded text

R. A. Hettinga <mailto: rah at ibuc.com>
The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

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