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

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This commit is contained in:
Andy Polyakov 2005-10-06 13:12:28 +00:00
parent ca04d7a208
commit 9b4eab501a
1 changed files with 55 additions and 32 deletions
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87
crypto/bn/bn_mont.c
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@ -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
ret->neg = r->neg;
x=ri;
rp=ret->d;
ap= &(r->d[x]);
if (r->top < x)
al=0;
else
al=r->top-x;
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;
ret->top=al;
rp=ret->d;
ap=&(r->d[ri]);
al-=4;
for (i=0; i<al; i+=4)
{
@ -221,7 +222,29 @@ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,
for (; i<al; i++)
rp[i]=ap[i];
#endif
#else /* !MONT_WORD */
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;
BN_CTX_start(ctx);
@ -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);
}