Import of old SSLeay release: SSLeay 0.9.1b (unreleased)

crypto/bn/bn_recp.c

@@ -60,66 +60,182 @@
 #include "cryptlib.h"
 #include "bn_lcl.h"
 
-int BN_mod_mul_reciprocal(r, x, y, m, i, nb, ctx)
+void BN_RECP_CTX_init(recp)
+BN_RECP_CTX *recp;
+	{
+	BN_init(&(recp->N));
+	BN_init(&(recp->Nr));
+	recp->num_bits=0;
+	recp->flags=0;
+	}
+
+BN_RECP_CTX *BN_RECP_CTX_new()
+	{
+	BN_RECP_CTX *ret;
+
+	if ((ret=(BN_RECP_CTX *)Malloc(sizeof(BN_RECP_CTX))) == NULL)
+		return(NULL);
+
+	BN_RECP_CTX_init(ret);
+	ret->flags=BN_FLG_MALLOCED;
+	return(ret);
+	}
+
+void BN_RECP_CTX_free(recp)
+BN_RECP_CTX *recp;
+	{
+	BN_free(&(recp->N));
+	BN_free(&(recp->Nr));
+	if (recp->flags & BN_FLG_MALLOCED)
+		Free(recp);
+	}
+
+int BN_RECP_CTX_set(recp,d,ctx)
+BN_RECP_CTX *recp;
+BIGNUM *d;
+BN_CTX *ctx;
+	{
+	BN_copy(&(recp->N),d);
+	BN_zero(&(recp->Nr));
+	recp->num_bits=BN_num_bits(d);
+	recp->shift=0;
+	return(1);
+	}
+
+int BN_mod_mul_reciprocal(r, x, y, recp, ctx)
 BIGNUM *r;
 BIGNUM *x;
 BIGNUM *y;
-BIGNUM *m;
-BIGNUM *i;
-int nb;
+BN_RECP_CTX *recp;
 BN_CTX *ctx;
 	{
-	int ret=0,j;
-	BIGNUM *a,*b,*c,*d;
+	int ret=0;
+	BIGNUM *a;
 
-	a=ctx->bn[ctx->tos++];
-	b=ctx->bn[ctx->tos++];
-	c=ctx->bn[ctx->tos++];
-	d=ctx->bn[ctx->tos++];
-
-	if (x == y)
-		{ if (!BN_sqr(a,x,ctx)) goto err; }
+	a= &(ctx->bn[ctx->tos++]);
+	if (y != NULL)
+		{
+		if (x == y)
+			{ if (!BN_sqr(a,x,ctx)) goto err; }
+		else
+			{ if (!BN_mul(a,x,y,ctx)) goto err; }
+		}
 	else
-		{ if (!BN_mul(a,x,y)) goto err; }
-	if (!BN_rshift(d,a,nb)) goto err;
-	if (!BN_mul(b,d,i)) goto err;
-	if (!BN_rshift(c,b,nb)) goto err;
-	if (!BN_mul(b,m,c)) goto err;
-	if (!BN_sub(r,a,b)) goto err;
+		a=x; /* Just do the mod */
+
+	BN_div_recp(NULL,r,a,recp,ctx);
+	ret=1;
+err:
+	ctx->tos--;
+	return(ret);
+	}
+
+int BN_div_recp(dv,rem,m,recp,ctx)
+BIGNUM *dv;
+BIGNUM *rem;
+BIGNUM *m;
+BN_RECP_CTX *recp;
+BN_CTX *ctx;
+	{
+	int i,j,tos,ret=0,ex;
+	BIGNUM *a,*b,*d,*r;
+
+	tos=ctx->tos;
+	a= &(ctx->bn[ctx->tos++]);
+	b= &(ctx->bn[ctx->tos++]);
+	if (dv != NULL)
+		d=dv;
+	else
+		d= &(ctx->bn[ctx->tos++]);
+	if (rem != NULL)
+		r=rem;
+	else
+		r= &(ctx->bn[ctx->tos++]);
+
+	if (BN_ucmp(m,&(recp->N)) < 0)
+		{
+		BN_zero(d);
+		BN_copy(r,m);
+		ctx->tos=tos;
+		return(1);
+		}
+
+	/* We want the remainder
+	 * Given input of ABCDEF / ab
+	 * we need multiply ABCDEF by 3 digests of the reciprocal of ab
+	 *
+	 */
+	i=BN_num_bits(m);
+
+	j=recp->num_bits*2;
+	if (j > i)
+		{
+		i=j;
+		ex=0;
+		}
+	else
+		{
+		ex=(i-j)/2;
+		}
+
+	j=i/2;
+
+	if (i != recp->shift)
+		recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N),
+			i,ctx);
+
+	if (!BN_rshift(a,m,j-ex)) goto err;
+	if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err;
+	if (!BN_rshift(d,b,j+ex)) goto err;
+	d->neg=0;
+	if (!BN_mul(b,&(recp->N),d,ctx)) goto err;
+	if (!BN_usub(r,m,b)) goto err;
+	r->neg=0;
+
 	j=0;
-	while (BN_cmp(r,m) >= 0)
+#if 1
+	while (BN_ucmp(r,&(recp->N)) >= 0)
 		{
 		if (j++ > 2)
 			{
 			BNerr(BN_F_BN_MOD_MUL_RECIPROCAL,BN_R_BAD_RECIPROCAL);
 			goto err;
 			}
-		if (!BN_sub(r,r,m)) goto err;
+		if (!BN_usub(r,r,&(recp->N))) goto err;
+		if (!BN_add_word(d,1)) goto err;
 		}
+#endif
 
+	r->neg=BN_is_zero(r)?0:m->neg;
+	d->neg=m->neg^recp->N.neg;
 	ret=1;
 err:
-	ctx->tos-=4;
+	ctx->tos=tos;
 	return(ret);
-	}
+	} 
 
-int BN_reciprocal(r, m,ctx)
+/* len is the expected size of the result
+ * We actually calculate with an extra word of precision, so
+ * we can do faster division if the remainder is not required.
+ */
+int BN_reciprocal(r,m,len,ctx)
 BIGNUM *r;
 BIGNUM *m;
+int len;
 BN_CTX *ctx;
 	{
-	int nm,ret= -1;
-	BIGNUM *t;
+	int ret= -1;
+	BIGNUM t;
 
-	t=ctx->bn[ctx->tos++];
+	BN_init(&t);
 
-	nm=BN_num_bits(m);
-	if (!BN_lshift(t,BN_value_one(),nm*2)) goto err;
+	BN_zero(&t);
+	if (!BN_set_bit(&t,len)) goto err;
 
-	if (!BN_div(r,NULL,t,m,ctx)) goto err;
-	ret=nm;
+	if (!BN_div(r,NULL,&t,m,ctx)) goto err;
+	ret=len;
 err:
-	ctx->tos--;
+	BN_free(&t);
 	return(ret);
 	}