Commit 4a0b6af9 authored by Nick Mathewson's avatar Nick Mathewson 🏃
Browse files

Ive spent about 10 hours benchmarking permutations on our counter-mode...

Ive spent about 10 hours benchmarking permutations on our counter-mode implementation.  This is the one that flies. (Avoid OpenSSL; optimizze rijndael calling convention to avoid needing to marshall and unmarshall counter.) This should speed up cell encryption by about 27%.


svn:r5486
parent 6443e5ec
......@@ -30,14 +30,14 @@ const char aes_c_id[] = "$Id$";
#include <openssl/evp.h>
#endif
/* For now, if OpenSSL supports AES, we always use the EVP_CIPHER_CTX version
* of it, so OpenSSL can use an engine instead if available. If the overhead
* turns out to suck, we should maybe switch to use OpenSSL's AES directly
* when no engine exists.
/* Benchmarking suggests that using the built-in rijndael below is
* significantly faster than using OpenSSL's EVP code (by about 27%)
* and faster than using OpenSSL's AES functions (by about 19%).
* The counter-mode optimization saves around 5%.
*/
#ifdef USE_OPENSSL_AES
#define USE_OPENSSL_EVP
#endif
#undef USE_OPENSSL_AES
#undef USE_OPENSSL_EVP
#define USE_RIJNDAEL_COUNTER_OPTIMIZATION
/*======================================================================*/
/* From rijndael-alg-fst.h */
......@@ -52,8 +52,12 @@ typedef uint8_t u8;
#define MAXNR 14
static int rijndaelKeySetupEnc(u32 rk[/*4*(Nr + 1)*/], const u8 cipherKey[], int keyBits);
#ifdef USE_RIJNDAEL_COUNTER_OPTIMIZATION
static void rijndaelEncrypt(const u32 rk[/*4*(Nr + 1)*/], int Nr, u32 ctr1, u32 ctr0, u8 ct[16]);
#else
static void rijndaelEncrypt(const u32 rk[/*4*(Nr + 1)*/], int Nr, const u8 pt[16], u8 ct[16]);
#endif
#endif
/*======================================================================*/
/* Interface to AES code, and counter implementation */
......@@ -77,7 +81,7 @@ struct aes_cnt_cipher {
* Helper function: set <b>cipher</b>'s internal buffer to the encrypted
* value of the current counter.
*/
static void
static INLINE void
_aes_fill_buf(aes_cnt_cipher_t *cipher)
{
/* We don't currently use OpenSSL's counter mode implementation because:
......@@ -86,6 +90,9 @@ _aes_fill_buf(aes_cnt_cipher_t *cipher)
* 3) changing the counter position was not trivial, last time I looked.
* None of these issues are insurmountable in principle.
*/
#if !defined(USE_OPENSSL_EVP) && !defined(USE_OPENSSL_AES) && defined(USE_RIJNDAEL_COUNTER_OPTIMIZATION)
rijndaelEncrypt(cipher->rk, cipher->nr, cipher->counter1, cipher->counter0, cipher->buf);
#else
u32 counter0 = cipher->counter0;
u32 counter1 = cipher->counter1;
u8 buf[16];
......@@ -109,6 +116,7 @@ _aes_fill_buf(aes_cnt_cipher_t *cipher)
#else
rijndaelEncrypt(cipher->rk, cipher->nr, buf, cipher->buf);
#endif
#endif
}
/**
......@@ -694,8 +702,13 @@ rijndaelKeySetupEnc(u32 rk[/*4*(Nr + 1)*/], const u8 cipherKey[], int keyBits)
return 0;
}
#ifdef USE_RIJNDAEL_COUNTER_OPTIMIZATION
void
rijndaelEncrypt(const u32 rk[/*4*(Nr + 1)*/], int Nr, u32 ctr1, u32 ctr0, u8 ct[16])
#else
void
rijndaelEncrypt(const u32 rk[/*4*(Nr + 1)*/], int Nr, const u8 pt[16], u8 ct[16])
#endif
{
u32 s0, s1, s2, s3, t0, t1, t2, t3;
#ifndef FULL_UNROLL
......@@ -706,10 +719,18 @@ rijndaelEncrypt(const u32 rk[/*4*(Nr + 1)*/], int Nr, const u8 pt[16], u8 ct[16]
* map byte array block to cipher state
* and add initial round key:
*/
#ifdef USE_RIJNDAEL_COUNTER_OPTIMIZATION
s0 = rk[0];
s1 = rk[1];
s2 = ctr1 ^ rk[2];
s3 = ctr0 ^ rk[3];
#else
s0 = GETU32(pt ) ^ rk[0];
s1 = GETU32(pt + 4) ^ rk[1];
s2 = GETU32(pt + 8) ^ rk[2];
s3 = GETU32(pt + 12) ^ rk[3];
#endif
#ifdef FULL_UNROLL
/* round 1: */
t0 = Te0[s0 >> 24] ^ Te1[(s1 >> 16) & 0xff] ^ Te2[(s2 >> 8) & 0xff] ^ Te3[s3 & 0xff] ^ rk[ 4];
......
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