On 01/02/2012 21:09, Jon Callas wrote:
As I remember Hal's protocol, it requires about eight megabytes of data to be transferred back and forth to prove that you know the SHA1 hash. It's not so much to be obviously absurd, but not efficient enough to be something you'd want to do often.
Close. If I get it correctly, it is a zero-knowledge proof, with one pass (leaving I guess <=50% odds of forgery) requiring 100 seconds and 22 kbytes of data (exchanged?), after some initial pre-computation requiring 40 minutes and 6MBytes of data (storage?), on a PC as it was circa 14 years ago. That, and more, is at 6'52" in the talk at http://video.google.com/videoplay?docid=-5745972992365920864 Hal Finney explains he got his result after careful optimizations, rewriting some SHA-1 internal operations as arithmetic operations in some appropriate field, rather than as boolean operations. Everything he says is convincing, but in 7 minutes there is not much detail, and so far I could not locate any later work (by him or others) claiming a comparable result. So it is hard to rule out that some error crept in his work. Francois Grieu _______________________________________________ cryptography mailing list cryptography@randombit.net http://lists.randombit.net/mailman/listinfo/cryptography
