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bug#13949: fill-paragraph is buggy, but using MD5 is even more buggy
From: |
Andreas Schwab |
Subject: |
bug#13949: fill-paragraph is buggy, but using MD5 is even more buggy |
Date: |
Mon, 28 Mar 2016 12:32:26 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.0.92 (gnu/linux) |
"Petros Travioli" <travioli@gmx.de> writes:
> But that's exactly what happens when you are using hash functions to
> verify buffer equality, just with a more complicated mathematical
> formulation and at a slightly different scale.
>
> So don't use hash functions to a two-sided correct answer to test buffer
> equality. For a one-sided answer (if hash(x) != hash(y) then x != y), you
> are fine.
There is a difference between a hash function and a cryptographic hash
function. An inportant property of a cryptographic hash function is the
avalanche effect, that means a small change in the plaintext will result
in a big change in the hash value. That makes such a hash function
suitable for the reverse condition x != y => hash(x) != hash(y), with a
very high probability of being true.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."