linux-kernel - Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAH8yC8m8hcL-gtWA_SbXOKSNRWV+nwzJRHBiEeMKEiz8ZR5M9Q@mail.gmail.com>
Date:	Wed, 4 May 2016 12:54:13 -0400
From:	Jeffrey Walton <noloader@...il.com>
To:	Stephan Mueller <smueller@...onox.de>
Cc:	"Theodore Ts'o" <tytso@....edu>, linux-kernel@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>, andi@...stfloor.org,
	Sandy Harris <sandyinchina@...il.com>,
	cryptography@...edaemon.net, jsd@...n.com, hpa@...or.com,
	linux-crypto@...r.kernel.org
Subject: Re: [PATCH 1/3] random: replace non-blocking pool with a
 Chacha20-based CRNG

>> +     chacha20_block(&crng->state[0], out);
>> +     if (crng->state[12] == 0)
>> +             crng->state[13]++;
>
> state[12]++? Or why do you increment the nonce?

In Bernstein's Salsa and ChaCha, the counter is 64-bit. It appears
ChaCha-TLS uses a 32-bit counter, and the other 32-bits is given to
the nonce.

Maybe the first question to ask is, what ChaCha is the kernel
providing? If its ChaCha-TLS, then the carry does not make a lot of
sense.

If the generator is limiting the amount of material under a given set
of security parameters (key and nonce), then the generator will likely
re-key itself long before the 256-GB induced wrap. In this case, it
does not matter which ChaCha the kernel is providing and the carry is
superfluous.

Jeff