Commit 9b4eab50 authored by Andy Polyakov's avatar Andy Polyakov
Browse files

Refine logic in bn_mont.c and eliminate redundant BN_CTX pulls.

parent ca04d7a2

crypto/bn/bn_mont.c

+55 −32
Original line number Diff line number Diff line
@@ -69,23 +69,27 @@ 


#define MONT_WORD /* use the faster word-based algorithm */



#ifdef MONT_WORD

static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont);

#endif



int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,

			  BN_MONT_CTX *mont, BN_CTX *ctx)

	{

	BIGNUM *tmp;

	int ret=0;

#ifdef OPENSSL_BN_ASM_MONT

#if defined(OPENSSL_BN_ASM_MONT) && defined(MONT_WORD)

	int num = mont->N.top;



	if (num>1 && a->top==num && b->top==num)

		{

		if (bn_wexpand(r,num) == NULL) return 0;

		if (bn_wexpand(r,num) == NULL) return(0);

		if (bn_mul_mont(r->d,a->d,b->d,mont->N.d,mont->n0,num))

			{

			r->neg = a->neg^b->neg;

			r->top = num;

			bn_fix_top(r);

			return 1;

			bn_correct_top(r);

			return(1);

			}

		}

#endif
@@ -104,7 +108,11 @@ int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, 
		if (!BN_mul(tmp,a,b,ctx)) goto err;

		}

	/* reduce from aRR to aR */

#ifdef MONT_WORD

	if (!BN_from_montgomery_word(r,tmp,mont)) goto err;

#else

	if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;

#endif

	bn_check_top(r);

	ret=1;

err:
@@ -112,35 +120,25 @@ err: 
	return(ret);

	}



int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,

	     BN_CTX *ctx)

	{

	int retn=0;



#ifdef MONT_WORD

	BIGNUM *n,*r;

static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont)

	{

	BIGNUM *n;

	BN_ULONG *ap,*np,*rp,n0,v,*nrp;

	int al,nl,max,i,x,ri;



	BN_CTX_start(ctx);

	if ((r = BN_CTX_get(ctx)) == NULL) goto err;



	if (!BN_copy(r,a)) goto err;

	n= &(mont->N);



	ap=a->d;

	/* mont->ri is the size of mont->N in bits (rounded up

	   to the word size) */

	al=ri=mont->ri/BN_BITS2;



	nl=n->top;

	if ((al == 0) || (nl == 0)) { r->top=0; return(1); }

	if ((al == 0) || (nl == 0)) { ret->top=0; return(1); }



	max=(nl+al+1); /* allow for overflow (no?) XXX */

	if (bn_wexpand(r,max) == NULL) goto err;

	if (bn_wexpand(ret,max) == NULL) goto err;

	if (bn_wexpand(r,max) == NULL) return(0);



	r->neg=a->neg^n->neg;

	r->neg^=n->neg;

	np=n->d;

	rp=r->d;

	nrp= &(r->d[nl]);
@@ -157,7 +155,7 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, 
	n0=mont->n0;



#ifdef BN_COUNT

	fprintf(stderr,"word BN_from_montgomery %d * %d\n",nl,nl);

	fprintf(stderr,"word BN_from_montgomery_word %d * %d\n",nl,nl);

#endif

	for (i=0; i<nl; i++)

		{
@@ -194,15 +192,18 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, 
#if 0

	BN_rshift(ret,r,mont->ri);

#else

	if (r->top < ri)

		{

		ret->top=0;

		return(1);

		}

	al=r->top-ri;

	if (bn_wexpand(ret,al) == NULL) return(0);

	ret->neg=r->neg;

	x=ri;

	rp=ret->d;

	ap= &(r->d[x]);

	if (r->top < x)

		al=0;

	else

		al=r->top-x;

	ret->top=al;



	rp=ret->d;

	ap=&(r->d[ri]);

	al-=4;

	for (i=0; i<al; i+=4)

		{
@@ -221,6 +222,28 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, 
	for (; i<al; i++)

		rp[i]=ap[i];

#endif



	if (BN_ucmp(ret, &(mont->N)) >= 0)

		{

		if (!BN_usub(ret,ret,&(mont->N))) return(0);

		}

	bn_check_top(ret);



	return(1);

	}

#endif	/* MONT_WORD */



int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,

	     BN_CTX *ctx)

	{

	int retn=0;

#ifdef MONT_WORD

	BIGNUM *t;



	BN_CTX_start(ctx);

	if ((t = BN_CTX_get(ctx)) && BN_copy(t,a))

		retn = BN_from_montgomery_word(ret,t,mont);

	BN_CTX_end(ctx);

#else /* !MONT_WORD */

	BIGNUM *t1,*t2;
@@ -238,7 +261,6 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, 
	if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;

	if (!BN_add(t2,a,t1)) goto err;

	if (!BN_rshift(ret,t2,mont->ri)) goto err;

#endif /* MONT_WORD */



	if (BN_ucmp(ret, &(mont->N)) >= 0)

		{
@@ -248,6 +270,7 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, 
	bn_check_top(ret);

 err:

	BN_CTX_end(ctx);

#endif /* MONT_WORD */

	return(retn);

	}