Commit 25439b76 authored by Bodo Möller's avatar Bodo Möller
Browse files

Move reduction step from BN_mod_exp to BN_mod_exp_mont_word. 

Fix BN_mod_exp_simple for a==0 (mod m).
Skip useless round in BN_mod_sqrt (1 is always a square, no need
to test BN_kronecker for it).
parent 3465dd38

crypto/bn/bn_exp.c

+9 −5
Original line number Diff line number Diff line
@@ -191,6 +191,7 @@ int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, 
	 */



#define MONT_MUL_MOD

#define MONT_EXP_WORD

#define RECP_MUL_MOD



#ifdef MONT_MUL_MOD
@@ -202,14 +203,14 @@ int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, 


	if (BN_is_odd(m))

		{

#  ifdef MONT_EXP_WORD

		if (a->top == 1 && !a->neg)

			{

			BN_ULONG A = a->d[0];

			if (m->top == 1)

				A %= m->d[0]; /* make sure that A is reduced */

			ret=BN_mod_exp_mont_word(r,A,p,m,ctx,NULL);

			}

		else

#  endif

			ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL);

		}

	else
@@ -505,11 +506,14 @@ int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, 
	bn_check_top(p);

	bn_check_top(m);



	if (!(m->d[0] & 1))

	if (m->top == 0 || !(m->d[0] & 1))

		{

		BNerr(BN_F_BN_MOD_EXP_MONT_WORD,BN_R_CALLED_WITH_EVEN_MODULUS);

		return(0);

		}

	if (m->top == 1)

		a %= m->d[0]; /* make sure that 'a' is reduced */



	bits = BN_num_bits(p);

	if (bits == 0)

		{
@@ -642,8 +646,8 @@ int BN_mod_exp_simple(BIGNUM *r, 
	if (!BN_nnmod(&(val[0]),a,m,ctx)) goto err;		/* 1 */

	if (BN_is_zero(&(val[0])))

		{

		ret = BN_one(r);

		return ret;

		ret = BN_zero(r);

		goto err;

		}



	window = BN_window_bits_for_exponent_size(bits);

crypto/bn/bn_sqrt.c

+3 −3
Original line number Diff line number Diff line
@@ -140,13 +140,13 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) 
	

	/* e > 1, so we really have to use the Tonelli/Shanks algorithm.

	 * First, find some  y  that is not a square. */

	i = 1;

	i = 2;

	do

		{

		/* For efficiency, try small numbers first;

		 * if this fails, try random numbers.

		 */

		if (i < 20)

		if (i < 22)

			{

			if (!BN_set_word(y, i)) goto end;

			}
@@ -171,7 +171,7 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) 
			goto end;

			}

		}

	while (r == 1 && i++ < 80);

	while (r == 1 && ++i < 82);

	

	if (r != -1)

		{