GNU bug report logs - #13949
24.3.50; `fill-paragraph' should not always put the buffer as modified

Previous Next

Full log

View this message in rfc822 format

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: "Petros Travioli" <travioli <at> gmx.de>
Cc: 13949 <at> debbugs.gnu.org
Subject: bug#13949: fill-paragraph is buggy, but using MD5 is even more buggy
Date: Mon, 28 Mar 2016 12:32:26 +0200

"Petros Travioli" <travioli <at> 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 <at> linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.