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optimize make_kn (from HEAD, by Andy)

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This commit is contained in:
Dr. Stephen Henson
2012-10-14 12:26:02 +00:00
parent fd9d2eaf16
commit 82607b291f
1 changed files with 7 additions and 9 deletions
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16
crypto/cmac/cmac.c
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@@ -77,19 +77,17 @@ struct CMAC_CTX_st
/* Make temporary keys K1 and K2 */
static void make_kn(unsigned char *k1, unsigned char *l, int bl)
static void make_kn(unsigned char *k1, const unsigned char *l, int bl)
{
int i;
unsigned char c = l[0], carry = c>>7, cnext;
/* Shift block to left, including carry */
for (i = 0; i < bl; i++)
{
k1[i] = l[i] << 1;
if (i < bl - 1 && l[i + 1] & 0x80)
k1[i] |= 1;
}
for (i = 0; i < bl-1; i++, c = cnext)
k1[i] = (c << 1) | ((cnext=l[i+1]) >> 7);
/* If MSB set fixup with R */
if (l[0] & 0x80)
k1[bl - 1] ^= bl == 16 ? 0x87 : 0x1b;
k1[i] = (c << 1) ^ ((0-carry)&(bl==16?0x87:0x1b));
}
CMAC_CTX *CMAC_CTX_new(void)