From 8cf982222913b9765561e8dbd8a975bc3ea1134b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Fri, 13 Apr 2012 17:00:50 +0200
Subject: [PATCH] Simplified aes_set_encrypt_key.
---
ChangeLog | 4 ++++
aes-set-encrypt-key.c | 40 ++++++++++++----------------------------
2 files changed, 16 insertions(+), 28 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index ff613329..2b4a4c32 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
2012-04-13 Niels Möller <nisse@lysator.liu.se>
+ * aes-set-encrypt-key.c (aes_set_encrypt_key): Use LE_READ_UINT32.
+ Tabulate the needed "round constants".
+ (xtime): Deleted function.
+
* aes-internal.h (SUBBYTE): Cast to uint32_t. Use B0, ..., B3
macros.
diff --git a/aes-set-encrypt-key.c b/aes-set-encrypt-key.c
index dfd102f7..0f7ac25a 100644
--- a/aes-set-encrypt-key.c
+++ b/aes-set-encrypt-key.c
@@ -34,26 +34,16 @@
#include "aes-internal.h"
#include "macros.h"
-static unsigned
-xtime(unsigned x)
-{
- assert (x < 0x100);
-
- x <<= 1;
- if (x & 0x100)
- x ^= 0x11b;
-
- assert (x < 0x100);
-
- return x;
-}
-
void
aes_set_encrypt_key(struct aes_ctx *ctx,
unsigned keysize, const uint8_t *key)
{
+ static const uint8_t rcon[10] = {
+ 0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36,
+ };
unsigned nk, nr, i, lastkey;
- uint32_t temp, rcon;
+ uint32_t temp;
+ const uint8_t *rp;
assert(keysize >= AES_MIN_KEY_SIZE);
assert(keysize <= AES_MAX_KEY_SIZE);
@@ -72,25 +62,19 @@ aes_set_encrypt_key(struct aes_ctx *ctx,
lastkey = (AES_BLOCK_SIZE/4) * (nr + 1);
ctx->nrounds = nr;
- rcon = 1;
- for (i=0; i<nk; i++)
- {
- ctx->keys[i] = key[i*4] + (key[i*4+1]<<8) + (key[i*4+2]<<16) +
- (key[i*4+3]<<24);
- }
+
+ for (i=0, rp = rcon; i<nk; i++)
+ ctx->keys[i] = LE_READ_UINT32(key + i*4);
for (i=nk; i<lastkey; i++)
{
temp = ctx->keys[i-1];
if (i % nk == 0)
- {
- temp = SUBBYTE(ROTL32(24, temp), aes_sbox) ^ rcon;
- rcon = (uint32_t)xtime((uint8_t)rcon&0xff);
- }
+ temp = SUBBYTE(ROTL32(24, temp), aes_sbox) ^ *rp++;
+
else if (nk > 6 && (i%nk) == 4)
- {
- temp = SUBBYTE(temp, aes_sbox);
- }
+ temp = SUBBYTE(temp, aes_sbox);
+
ctx->keys[i] = ctx->keys[i-nk] ^ temp;
}
}
--
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