linux-kernel - Re: [PATCH 3/7] crypto: powerpc/md5 - Remove PowerPC optimized MD5 code

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Message-ID: <20250803221438.GA119835@quark>
Date: Sun, 3 Aug 2025 15:14:38 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: Segher Boessenkool <segher@...nel.crashing.org>
Cc: linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>, linux-mips@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org
Subject: Re: [PATCH 3/7] crypto: powerpc/md5 - Remove PowerPC optimized MD5
 code

On Sun, Aug 03, 2025 at 05:07:10PM -0500, Segher Boessenkool wrote:
> On Sun, Aug 03, 2025 at 01:44:29PM -0700, Eric Biggers wrote:
> > MD5 is insecure,
> 
> Really?  Have you found an attack?  Can you explain it to the rest of
> the world?
> 
> MD5 is not recommended for future cryptographic purposes, there have
> been some collission "attacks" on it (quotes because such a thing is
> never an attack at all, merely an indication that not all is well with
> it, somewhere in the future an actual vulnerability might be found).
> 
> Since there are newer, better, *cheaper* alternatives available, of
> course you should not use MD5 for anything new anymore.  But claiming it
> is insecure is FUD.

Many attacks, including practical attacks, have been found on MD5 over
the past few decades.  Check out https://en.wikipedia.org/wiki/MD5

> > This commit removes the PowerPC optimized MD5 code.
> 
> Why?  It would help to have real arguments for it!

Sure, check out the commit message which mentioned multiple reasons why
maintaining this code is not worthwhile.

- Eric