From: Eric Biggers <ebiggers@kernel.org>
To: Samuel Neves <samuel.c.p.neves@gmail.com>
Cc: Paul Crowley <paulcrowley@google.com>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
linux-fscrypt@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Herbert Xu <herbert@gondor.apana.org.au>,
Greg Kaiser <gkaiser@google.com>,
Michael Halcrow <mhalcrow@google.com>,
tomer.ashur@esat.kuleuven.be, Eric Biggers <ebiggers@google.com>,
"D. J. Bernstein" <djb@cr.yp.to>
Subject: Re: [RFC PATCH 3/9] crypto: chacha20-generic - refactor to allow varying number of rounds
Date: Tue, 7 Aug 2018 14:51:21 -0700 [thread overview]
Message-ID: <20180807215121.GB25300@gmail.com> (raw)
In-Reply-To: <CAEX_ruFp0KddnZyetZt997OvRzKDuN7U95MF_N9AgTh+mTcD7Q@mail.gmail.com>
On Tue, Aug 07, 2018 at 11:21:04AM +0100, Samuel Neves wrote:
> > The best attack on ChaCha breaks 7 rounds, and that attack requires 2^248 operations.
>
> This number, as far as I can tell, comes from the "New features of
> Latin dances" paper. There have been some minor improvements in the
> intervening 10 years, e.g., [1, 2, 3, 4], which pull back the
> complexity of breaking ChaCha7 down to 2^235. In any case, every
> attack so far appears to hit a wall at 8 rounds, with 12 rounds---the
> recommended eSTREAM round number for Salsa20---seeming to offer a
> reasonable security margin, still somewhat better than that of the
> AES.
>
> Best regards,
> Samuel Neves
>
> [1] https://eprint.iacr.org/2015/698
> [2] https://eprint.iacr.org/2015/217
> [3] https://eprint.iacr.org/2016/1034
> [4] https://doi.org/10.1016/j.dam.2017.04.034
Thanks Samuel, I'll fix that number in the next iteration of the patchset.
- Eric
next prev parent reply other threads:[~2018-08-07 21:51 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-06 22:32 [RFC PATCH 0/9] crypto: HPolyC support Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 1/9] crypto: chacha20-generic - add HChaCha20 library function Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 2/9] crypto: chacha20-generic - add XChaCha20 support Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 3/9] crypto: chacha20-generic - refactor to allow varying number of rounds Eric Biggers
2018-08-06 23:16 ` Jason A. Donenfeld
2018-08-06 23:48 ` Paul Crowley
2018-08-07 0:15 ` Jason A. Donenfeld
2018-08-07 1:06 ` Paul Crowley
2018-08-07 10:21 ` Samuel Neves
2018-08-07 21:51 ` Eric Biggers [this message]
2018-08-08 0:15 ` Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 4/9] crypto: chacha - add XChaCha12 support Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 5/9] crypto: arm/chacha20 - add XChaCha20 support Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 6/9] crypto: arm/chacha20 - refactor to allow varying number of rounds Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 7/9] crypto: arm/chacha - add XChaCha12 support Eric Biggers
2018-08-06 22:32 ` [RFC PATCH 8/9] crypto: arm/poly1305 - add NEON accelerated Poly1305 implementation Eric Biggers
2018-08-07 12:09 ` Ard Biesheuvel
2018-08-07 23:19 ` Eric Biggers
2018-08-22 10:00 ` Ard Biesheuvel
2018-08-06 22:33 ` [RFC PATCH 9/9] crypto: hpolyc - add support for the HPolyC encryption mode Eric Biggers
2018-08-06 23:04 ` [PATCH] crypto: remove speck Jason A. Donenfeld
2018-08-07 1:03 ` Jeffrey Walton
2018-08-07 20:18 ` Eric Biggers
2018-08-07 1:19 ` Eric Biggers
2018-08-07 2:38 ` Jason A. Donenfeld
2018-08-07 3:12 ` Eric Biggers
2018-08-07 3:15 ` Theodore Y. Ts'o
2018-08-07 12:51 ` Ard Biesheuvel
2018-08-07 6:22 ` [PATCH v2] crypto: remove Speck Jason A. Donenfeld
2018-08-07 6:57 ` Ard Biesheuvel
2018-09-04 4:55 ` Herbert Xu
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