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Improve BN_mod_inverse performance.

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Get the BN_mod_exp_mont bugfix (for handling negative inputs) correct
this time.
This commit is contained in:
Bodo Möller 2000-11-29 09:41:19 +00:00
parent 0135e33511
commit 499e167fda
4 changed files with 164 additions and 19 deletions
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6
CHANGES
View File

@ -3,6 +3,12 @@
Changes between 0.9.6 and 0.9.7 [xx XXX 2000]
*) Make BN_mod_inverse faster by explicitly handling small quotients
in the Euclid loop instead of always using BN_div.
(Speed gain about 20% for small moduli [256 or 512 bits], about
30% for larger ones [1024 or 2048 bits].)
[Bodo Moeller]
*) Disable ssl2_peek and ssl3_peek (i.e., both implementations
of SSL_peek) because they both are completely broken.
They will be fixed RSN by adding an additional 'peek' parameter

2
crypto/bn/bn_exp.c
View File

@ -376,7 +376,7 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
BN_init(&val[0]);
ts=1;
if (!a->neg && BN_ucmp(a,m) >= 0)
if (a->neg || BN_ucmp(a,m) >= 0)
{
if (!BN_nnmod(&(val[0]),a,m,ctx))
goto err;

81
crypto/bn/bn_gcd.c
View File

@ -204,7 +204,7 @@ err:
BIGNUM *BN_mod_inverse(BIGNUM *in,
const BIGNUM *a, const BIGNUM *n, BN_CTX *ctx)
{
BIGNUM *A,*B,*X,*Y,*M,*D,*R=NULL;
BIGNUM *A,*B,*X,*Y,*M,*D,*T,*R=NULL;
BIGNUM *ret=NULL;
int sign;
@ -218,7 +218,8 @@ BIGNUM *BN_mod_inverse(BIGNUM *in,
D = BN_CTX_get(ctx);
M = BN_CTX_get(ctx);
Y = BN_CTX_get(ctx);
if (Y == NULL) goto err;
T = BN_CTX_get(ctx);
if (T == NULL) goto err;
if (in == NULL)
R=BN_new();
@ -253,7 +254,47 @@ BIGNUM *BN_mod_inverse(BIGNUM *in,
* -sign*Y*a == A (mod |n|)
*/
if (!BN_div(D,M,A,B,ctx)) goto err;
/* (D, M) := (A/B, A%B) ... */
if (BN_num_bits(A) == BN_num_bits(B))
{
if (!BN_one(D)) goto err;
if (!BN_sub(M,A,B)) goto err;
}
else if (BN_num_bits(A) == BN_num_bits(B) + 1)
{
/* A/B is 1, 2, or 3 */
if (!BN_lshift1(T,B)) goto err;
if (BN_ucmp(A,T) < 0)
{
/* A < 2*B, so D=1 */
if (!BN_one(D)) goto err;
if (!BN_sub(M,A,B)) goto err;
}
else
{
/* A >= 2*B, so D=2 or D=3 */
if (!BN_sub(M,A,T)) goto err;
if (!BN_add(D,T,B)) goto err; /* use D (:= 3*B) as temp */
if (BN_ucmp(A,D) < 0)
{
/* A < 3*B, so D=2 */
if (!BN_set_word(D,2)) goto err;
/* M (= A - 2*B) already has the correct value */
}
else
{
/* only D=3 remains */
if (!BN_set_word(D,3)) goto err;
/* currently M = A - 2*B, but we need M = A - 3*B */
if (!BN_sub(M,M,B)) goto err;
}
}
}
else
{
if (!BN_div(D,M,A,B,ctx)) goto err;
}
/* Now
* A = D*B + M;
* thus we have
@ -286,8 +327,33 @@ BIGNUM *BN_mod_inverse(BIGNUM *in,
* Note that X and Y stay non-negative all the time.
*/
if (!BN_mul(tmp,D,X,ctx)) goto err;
if (!BN_add(tmp,tmp,Y)) goto err;
/* most of the time D is very small, so we can optimize tmp := D*X+Y */
if (BN_is_one(D))
{
if (!BN_add(tmp,X,Y)) goto err;
}
else
{
if (BN_is_word(D,2))
{
if (!BN_lshift1(tmp,X)) goto err;
}
else if (BN_is_word(D,3))
{
if (!BN_lshift1(tmp,X)) goto err;
if (!BN_add(tmp,tmp,X)) goto err;
}
else if (BN_is_word(D,4))
{
if (!BN_lshift(tmp,X,2)) goto err;
}
else
{
if (!BN_mul(tmp,D,X,ctx)) goto err;
}
if (!BN_add(tmp,tmp,Y)) goto err;
}
M=Y; /* keep the BIGNUM object, the value does not matter */
Y=X;
X=tmp;
@ -312,7 +378,10 @@ BIGNUM *BN_mod_inverse(BIGNUM *in,
if (BN_is_one(A))
{
/* Y*a == 1 (mod |n|) */
if (!BN_mod(R,Y,n,ctx)) goto err;
if (BN_ucmp(Y,n) < 0)
if (!BN_copy(R,Y)) goto err;
else
if (!BN_nnmod(R,Y,n,ctx)) goto err;
}
else
{

94
crypto/bn/expspeed.c
View File

@ -60,7 +60,16 @@
/* most of this code has been pilfered from my libdes speed.c program */
#define BASENUM 5000
#define BASENUM 10000
#define NUM_START 0
/* determine timings for modexp, gcd, or modular inverse */
#define TEST_EXP
#undef TEST_GCD
#undef TEST_INV
#undef PROG
#define PROG bnspeed_main
@ -161,11 +170,30 @@ static double Time_F(int s)
#endif
}
#define NUM_SIZES 6
static int sizes[NUM_SIZES]={256,512,1024,2048,4096,8192};
static int mul_c[NUM_SIZES]={8*8*8*8*8,8*8*8*8,8*8*8,8*8,8,1};
#define NUM_SIZES 7
#if NUM_START > NUM_SIZES
# error "NUM_START > NUM_SIZES"
#endif
static int sizes[NUM_SIZES]={128,256,512,1024,2048,4096,8192};
static int mul_c[NUM_SIZES]={8*8*8*8*8*8,8*8*8*8*8,8*8*8*8,8*8*8,8*8,8,1};
/*static int sizes[NUM_SIZES]={59,179,299,419,539}; */
#define RAND_SEED(string) { const char str[] = string; RAND_seed(string, sizeof string); }
static void genprime_cb(int p, int n, void *arg)
{
char c='*';
if (p == 0) c='.';
if (p == 1) c='+';
if (p == 2) c='*';
if (p == 3) c='\n';
putc(c, stderr);
fflush(stderr);
(void)n;
(void)arg;
}
void do_mul_exp(BIGNUM *r,BIGNUM *a,BIGNUM *b,BIGNUM *c,BN_CTX *ctx);
int main(int argc, char **argv)
@ -179,6 +207,10 @@ int main(int argc, char **argv)
c=BN_new();
r=BN_new();
while (!RAND_status())
/* not enough bits */
RAND_SEED("I demand a manual recount!");
do_mul_exp(r,a,b,c,ctx);
}
@ -188,23 +220,61 @@ void do_mul_exp(BIGNUM *r, BIGNUM *a, BIGNUM *b, BIGNUM *c, BN_CTX *ctx)
double tm;
long num;
#if defined(TEST_EXP) + defined(TEST_GCD) + defined(TEST_INV) != 1
# error "choose one test"
#endif
#ifdef TEST_INV
# define C_PRIME
#endif
num=BASENUM;
for (i=0; i<NUM_SIZES; i++)
for (i=NUM_START; i<NUM_SIZES; i++)
{
BN_pseudo_rand(a,sizes[i],1,0);
BN_pseudo_rand(b,sizes[i],1,0);
BN_pseudo_rand(c,sizes[i],1,1);
BN_mod(a,a,c,ctx);
BN_mod(b,b,c,ctx);
#ifdef C_PRIME
if (!BN_generate_prime(c,sizes[i],0,NULL,NULL,genprime_cb,NULL)) goto err;
putc('\n', stderr);
fflush(stderr);
#endif
Time_F(START);
for (k=0; k<num; k++)
BN_mod_exp(r,a,b,c,ctx);
{
if (k%50 == 0) /* Average over num/50 different choices of random numbers. */
{
if (!BN_pseudo_rand(a,sizes[i],1,0)) goto err;
if (!BN_pseudo_rand(b,sizes[i],1,0)) goto err;
#ifndef C_PRIME
if (!BN_pseudo_rand(c,sizes[i],1,1)) goto err;
#endif
}
#if defined(TEST_EXP)
if (!BN_mod_exp(r,a,b,c,ctx)) goto err;
#elif defined(TEST_GCD)
if (!BN_gcd(r,a,b,ctx)) goto err;
if (!BN_gcd(r,b,c,ctx)) goto err;
if (!BN_gcd(r,b,c,ctx)) goto err;
#else /* TEST_INV */
if (!BN_mod_inverse(r,a,c,ctx)) goto err;
if (!BN_mod_inverse(r,b,c,ctx)) goto err;
#endif
}
tm=Time_F(STOP);
printf("mul %4d ^ %4d %% %d -> %8.3fms %5.1f\n",sizes[i],sizes[i],sizes[i],tm*1000.0/num,tm*mul_c[i]/num);
printf(
#if defined(TEST_EXP)
"modexp %4d ^ %4d %% %4d"
#elif defined(TEST_GCD)
"3*gcd %4d %4d %4d"
#else /* TEST_INV */
"2*inv %4d %4d mod %4d"
#endif
" -> %8.3fms %5.1f (%d)\n",sizes[i],sizes[i],sizes[i],tm*1000.0/num,tm*mul_c[i]/num, num);
num/=7;
if (num <= 0) num=1;
}
return;
err:
ERR_print_errors_fp(stderr);
}