From 09fbf7c0f24176ef3b450c590f220ed8033dd2c3 Mon Sep 17 00:00:00 2001 From: Jarod Wilson Date: Mon, 24 Nov 2008 21:20:13 +0800 Subject: crypto: ansi_cprng - fix inverted DT increment routine 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 Acked-by: Neil Horman Signed-off-by: Herbert Xu --- crypto/ansi_cprng.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c index 1b3b1da1fd3..0fac8ffc2fb 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; -- cgit v1.2.3-18-g5258