Cryptology ePrint Archive: Report 2005/356
Exponential Memory-Bound Functions for Proof of Work Protocols
Abstract: In Year 2005, Internet users were twice more likely to receive
unsolicited electronic messages, known as spams, than regular emails.
Proof of work protocols are designed to deter such phenomena
and other denial-of-service attacks by requiring computed stamps
based on hard-to-solve problems with easy-to-verify solutions.
As cpu-intensive computations are badly hit over time by Moore's law,
memory-bound computations have been suggested to deal with heterogeneous hardware.
We introduce new practical, optimal, proven and possibly memory-bound
functions suitable to these protocols,
in which the client-side work to compute the response is intrinsically
exponential with respect to the server-side work needed to set or check the challenge.
One-way non-interactive solution-verification variants are also presented.
Although simple implementations of such functions are bound
by memory latency, optimized versions are shown to be bound
by memory bandwidth instead.
Category / Keywords: cryptographic protocols / electronic commerce and payment
Publication Info: Submitted to a conference. TR Ecole des mines de Paris A/370/CRI.
Date: received 3 Oct 2005, last revised 7 Nov 2006
Contact author: fabien coelho at ensmp fr
Available format(s): PDF | BibTeX Citation
Note: Overall presentation simplified by focussing on one variant.
Proof of the scheme added, including an optimality claim, replacing a lot of hand-waving.
Version: 20061107:100848 (All versions of this report)
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