From: Neil Horman Subject: Re: [PATCH] crypto: ansi_cprng: fix inverted DT increment routine Date: Thu, 13 Nov 2008 13:44:31 -0500 Message-ID: <20081113184431.GB18604@hmsendeavour.rdu.redhat.com> References: <200811131136.15875.jarod@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au, davem@davemloft.net, linux-kernel@vger.kernel.org To: Jarod Wilson Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:34929 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752185AbYKMSqo (ORCPT ); Thu, 13 Nov 2008 13:46:44 -0500 Content-Disposition: inline In-Reply-To: <200811131136.15875.jarod@redhat.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Thu, Nov 13, 2008 at 11:36:11AM -0500, Jarod Wilson wrote: > The ANSI X9.31 PRNG docs aren't particularly clear on how to increment DT, > but empirical testing shows we're incrementing from the wrong end. A 10,000 > iteration Monte Carlo RNG test currently winds up not getting the expected > result. > > From http://csrc.nist.gov/groups/STM/cavp/documents/rng/RNGVS.pdf : > > # CAVS 4.3 > # ANSI931 MCT > [X9.31] > [AES 128-Key] > > COUNT = 0 > Key = 9f5b51200bf334b5d82be8c37255c848 > DT = 6376bbe52902ba3b67c925fa701f11ac > V = 572c8e76872647977e74fbddc49501d1 > R = 48e9bd0d06ee18fbe45790d5c3fc9b73 > > Currently, we get 0dd08496c4f7178bfa70a2161a79459a after 10000 loops. > > Inverting the DT increment routine results in us obtaining the expected result > of 48e9bd0d06ee18fbe45790d5c3fc9b73. Verified on both x86_64 and ppc64. > > Signed-off-by: Jarod Wilson > > --- > > crypto/ansi_cprng.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c > index 486aa93..a7c703d 100644 > --- a/crypto/ansi_cprng.c > +++ b/crypto/ansi_cprng.c > @@ -161,7 +161,7 @@ static int _get_more_prng_bytes(struct prng_context *ctx) > /* > * Now update our DT value > */ > - for (i = 0; i < DEFAULT_BLK_SZ; i++) { > + for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) { > ctx->DT[i] += 1; > if (ctx->DT[i] != 0) > break; > > -- > Jarod Wilson > jarod@redhat.com > > Looks good, thanks Jarod! Acked-by: Neil Horman -- /*************************************************** *Neil Horman *nhorman@tuxdriver.com *gpg keyid: 1024D / 0x92A74FA1 *http://pgp.mit.edu ***************************************************/