"Stanislav Malyshev a.k.a Frodo" <[EMAIL PROTECTED]> wrote:
> Didn't they learn you in your math class that *any* hash that isn't equal
> by length with hashed objects will collide objects? It's called Dirichlet
> principle, IIRC - if you have 3 objects and 2 signatures, 2 objects must
> have identical signature. Think about it.
While this is strictly speaking true, it also should be remembered that with
random objects, which large files essentially are, the big number theorems come
into the play. Think of md5 or PGP signatures. Being of a negligible size
comparing to the files themselves, they serve as a very reliable authentication
token. Same could be done here, i.e. instead of comparing (huge) files one
compares their signatures. Performance is a separate topic anyway, of course,
but using a multi-step adaptive comparison algorithm, one could probably gain
the typical log(N)/N reduction factor.
Regards,
Evgeny
--
____________________________________________________________
/ Evgeny Stambulchik <[EMAIL PROTECTED]> \
/ Plasma Laboratory, Weizmann Institute of Science, Israel \ \
| Phone : (972)8-934-3610 == | == FAX : (972)8-934-3491 | |
| URL : http://plasma-gate.weizmann.ac.il/~fnevgeny/ | |
| Finger for PGP key >=====================================+ |
|______________________________________________________________|
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