From: rasky <rasky@38d2e660-2303-0410-9eaa-f027e97ec537>
Date: Tue, 5 Oct 2010 17:49:39 +0000 (+0000)
Subject: SEC: Isaac: change reseeding algorithm by xoring the new seed over the
X-Git-Tag: 2.6.0~5^2~105
X-Git-Url: https://codewiz.org/gitweb?a=commitdiff_plain;h=ebd1541f1666aad733559ecd07ce6c04d7e86dcf;p=bertos.git

SEC: Isaac: change reseeding algorithm by xoring the new seed over the
current context. This allows an initial full seeding.


git-svn-id: https://src.develer.com/svnoss/bertos/trunk@4415 38d2e660-2303-0410-9eaa-f027e97ec537
---

diff --git a/bertos/sec/prng/isaac.c b/bertos/sec/prng/isaac.c
index 4e031c0b..f3320a54 100644
--- a/bertos/sec/prng/isaac.c
+++ b/bertos/sec/prng/isaac.c
@@ -107,9 +107,9 @@ static void isaac_reseed(PRNG *ctx_, const uint8_t *seed)
 	ub4 a,b,c,d,e,f,g,h;
 	ub4 *m,*r;
 
-	// Copy seed over half of randrsl, to reuse half of last-generated
-	// data as seed.
-	memcpy(ctx->randrsl, seed, sizeof(ctx->randrsl)/2);
+	// XOR the new seed over the current state, so to depend on
+	// the previously-generated output.
+	xor_block(ctx->randrsl, ctx->randrsl, seed, sizeof(ctx->randrsl));
 
 	ctx->randa = ctx->randb = ctx->randc = 0;
 	m=ctx->randmem;
@@ -172,7 +172,7 @@ void isaac_init(IsaacContext *ctx)
 {
 	ctx->prng.reseed = isaac_reseed;
 	ctx->prng.generate = isaac_generate;
-	ctx->prng.seed_len = sizeof(ctx->randrsl) / 2;
+	ctx->prng.seed_len = sizeof(ctx->randrsl);
 	ctx->prng.seeded = 0;
 
 	ctx->randcnt = CONFIG_ISAAC_RANDSIZ*4;