From 499e167fda19e01d384fb093f18447b5051d5da9 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Bodo=20M=C3=B6ller?= Date: Wed, 29 Nov 2000 09:41:19 +0000 Subject: [PATCH] Improve BN_mod_inverse performance. Get the BN_mod_exp_mont bugfix (for handling negative inputs) correct this time. --- CHANGES | 6 +++ crypto/bn/bn_exp.c | 2 +- crypto/bn/bn_gcd.c | 81 +++++++++++++++++++++++++++++++++++--- crypto/bn/expspeed.c | 94 ++++++++++++++++++++++++++++++++++++++------ 4 files changed, 164 insertions(+), 19 deletions(-) diff --git a/CHANGES b/CHANGES index 998ea1639c..7a5bac81d0 100644 --- a/CHANGES +++ b/CHANGES @@ -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 diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index eab394b962..35ab56efc0 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -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; diff --git a/crypto/bn/bn_gcd.c b/crypto/bn/bn_gcd.c index ea6816a43f..d53f32656b 100644 --- a/crypto/bn/bn_gcd.c +++ b/crypto/bn/bn_gcd.c @@ -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 { diff --git a/crypto/bn/expspeed.c b/crypto/bn/expspeed.c index 99cf2c52a8..5f76aa4126 100644 --- a/crypto/bn/expspeed.c +++ b/crypto/bn/expspeed.c @@ -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 %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); } -- 2.25.1