Subject: Re: bug#13949: 24.4.1; `fill-paragraph' should not always put the buffer as modified

From: Lars Magne Ingebrigtsen <[email-masked]>
Date: Sun, 27 Mar 2016 17:35:25 +0200

Dmitry Gutov <[email-masked]> writes:

> On 03/27/2016 06:31 AM, Óscar Fuentes wrote:
>
>> +  (when (and (not (string= h ""))
>> +             (string= h (secure-hash 'md5 (current-buffer))))
>> +    (set-buffer-modified-p nil)))
>
> Hashes have collisions (and md5 is a bit famous for them). So in
> principle, I don't think using a hash is a good choice in this case.

md5 is famous for enabling attackers to construct strings with the same
hash, not for arbitrarily making strings hash to the same result.

It's less likely that the before/after `M-q' strings hash to the same
md5 than cosmic rays reprogramming your Emacs into vi, so:

> Either way, you'd have to keep the original string around, to compare
> against if the hashes match.

Not really.

(Ok, I'm exaggerating.  Slightly!)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no