Author: mav
Date: Tue Dec 16 13:58:37 2008
New Revision: 186179
URL: http://svn.freebsd.org/changeset/base/186179
Log:
Avoid 256 integer divisions per rc4_init() call. Replace it with using
separate index variable.
It gives more then double rc4_init() performance increase on tested i386 P4.
It also gives about 15% speedup to PPTP VPN with stateless MPPE encryption
(by ng_mppc) which calls rc4_init() for every packet.
Modified:
head/sys/crypto/rc4/rc4.c
Modified: head/sys/crypto/rc4/rc4.c
==============================================================================
--- head/sys/crypto/rc4/rc4.c Tue Dec 16 11:06:30 2008 (r186178)
+++ head/sys/crypto/rc4/rc4.c Tue Dec 16 13:58:37 2008 (r186179)
@@ -61,7 +61,7 @@ void
rc4_init(struct rc4_state *const state, const u_char *key, int keylen)
{
u_char j;
- int i;
+ int i, k;
/* Initialize state with identity permutation */
for (i = 0; i < 256; i++)
@@ -70,9 +70,11 @@ rc4_init(struct rc4_state *const state,
state->index2 = 0;
/* Randomize the permutation using key data */
- for (j = i = 0; i < 256; i++) {
- j += state->perm[i] + key[i % keylen];
+ for (j = i = k = 0; i < 256; i++) {
+ j += state->perm[i] + key[k];
swap_bytes(&state->perm[i], &state->perm[j]);
+ if (++k >= keylen)
+ k = 0;
}
}
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