RPOW - Reusable Proofs of Work

[bear]

On Tue, 17 Aug 2004, Hal Finney wrote:

>A couple of quick responses to the questions on RPOW, as I am at
>Crypto this week.

I'm wondering how applicable RPOW is.  Generally speaking, all
the practical applications I can think of for a proof-of-work
are defeated if proofs-of-work are storable, transferable, or
reusable.  Once they're storable, tranferable, and reusable,
aren't we restricted to applications already nailed down by
digital cash schemes?

So, even if it works flawlessly, this seems like an exercise
of cleverness that makes a cryptographic entity *less* generally
useful than the primitive from which it's derived. It probably
has a few specialized applications that normal POWs won't serve;
I just haven't been able to distinguish them from the applications
served by digital cash.

Why doesn't this scheme give rise to a "POW server" that just
sits there, generating proofs-of-work in advance of need and
dispensing them at request?  Or even to a company that sells
POW's to people who can't be bothered to run their own server?
And doesn't such a device or service defeat the use of POWs
for real-time load balancing, traffic control, etc?

				Bear

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