Re: [Asrg] 3 (Message Verification) - Viability of hashcash-based signatures (was: E-postage from first principles)
Jonathan Morton <chromi@chromatix.demon.co.uk> Sat, 01 May 2004 00:10 UTC
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From: Jonathan Morton <chromi@chromatix.demon.co.uk>
Subject: Re: [Asrg] 3 (Message Verification) - Viability of hashcash-based signatures (was: E-postage from first principles)
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Date: Sat, 01 May 2004 00:44:50 +0100
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> - The stamp optionally includes a signature to facilitate > whitelisting. This can reduce the hashcash demanded from regular > correspondents to as low as 8 bits, which is computationally > trivial... > > ...If nobody happens to have a Z80 and a compiler to hand, I'll put in > some work and try it for the 6502 instead - I have a handful of old > BBC Micros lying around. To answer my own question, I've worked out that a 6502 can process an SHA-1 block in about 40000 cycles, which compares surprisingly well to the 68030 (and begs an investigation into precisely why the '030 is so inefficient). This is completely untested code - I didn't even type it into the machine, just worked out the timing piecemeal from the assembly manual - but the ballpark figure should be accurate. To put this in perspective, it means that my 1982-vintage BBC Micros (with 2MHz 6502 chips) should be able to mint 8-bit hashcash in about 5 seconds on average, and most other 8-bit accumulator machines (including the Z80 family) should be comparable. This, in turn, means that my whitelist-grade signature scheme should be computationally feasible for pretty much every "computer" capable of running a TCP/IP stack. This encourages me to continue working on a more detailed spec for discussion. Code size may be more of a problem, however, as the 40000-cycle performance assumes a fairly unrolled-loop code configuration, which consumes a significant portion of a 16-bit address space (exact size not calculated, but 4-8KB is possible). It also assumes a fixed area of RAM, including 25 bytes of zero page and 340 bytes elsewhere, is available and hard-coded into the program. For machines with a paged ROM system and a half-decent memory map, this shouldn't be a serious problem, but for some microcontrollers it may require a tradeoff of code size and/or position-independence against performance. In any case, it is certainly no problem for any truly 32-bit machine. -------------------------------------------------------------- from: Jonathan "Chromatix" Morton mail: chromi@chromatix.demon.co.uk website: http://www.chromatix.uklinux.net/ tagline: The key to knowledge is not to rely on people to teach you it. _______________________________________________ Asrg mailing list Asrg@ietf.org https://www1.ietf.org/mailman/listinfo/asrg
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- [Asrg] (no subject) Richard Willey
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- RE: [Asrg] (no subject) Hallam-Baker, Phillip
- Re: [Asrg] (no subject) Devdas Bhagat
- RE: [Asrg] (no subject) Hallam-Baker, Phillip
- Re: [Asrg] (no subject) Barry Shein
- RE: [Asrg] (no subject) Hallam-Baker, Phillip
- The end result of E-postage (was Re: [Asrg] (no s… Alan DeKok
- RE: [Asrg] (no subject) Barry Shein
- RE: [Asrg] (no subject) Hallam-Baker, Phillip
- RE: [Asrg] (no subject) Barry Shein
- Re: [Asrg] (no subject) Roger B.A. Klorese
- Re: [Asrg] (no subject) Barry Shein
- Re: [Asrg] (no subject) "Roger B.A. Klorese "
- [Asrg] E-postage from first principles John Levine
- Re: [Asrg] E-postage from first principles Jonathan Morton
- Re: [Asrg] E-postage from first principles John Levine
- Re: [Asrg] E-postage from first principles Jonathan Morton
- [Asrg] Re: Consent protocols - was E-postage John Levine
- [Asrg] Consent protocols - was E-postage David Maxwell
- [Asrg] Re: Consent protocols - was E-postage David Maxwell
- Re: [Asrg] (no subject) Barry Shein
- Re: [Asrg] E-postage from first principles Barry Shein
- Re: [Asrg] E-postage from first principles Yakov Shafranovich
- [Asrg] Re: Consent protocols - was E-postage John Levine
- Re: [Asrg] (no subject) Roger B.A. Klorese
- [Asrg] Re: Consent protocols - was E-postage John Levine
- [Asrg] Re: Consent protocols - was E-postage David Maxwell
- Re: [Asrg] (no subject) Barry Shein
- Re: [Asrg] (no subject) "Roger B.A. Klorese"
- Re: [Asrg] 3 (Message Verification) - Viability o… Jonathan Morton
- [Asrg] Re: Consent protocols - was E-postage David Maxwell
- [Asrg] (no subject) Paul Lambert