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

[openssl.git] / crypto / bn / bn_recp.c

diff --git a/crypto/bn/bn_recp.c b/crypto/bn/bn_recp.c
index 72cd69d3fc9c76efbf06c43df8724a221dba6226..97ca857ed1b2463428b1504c79e248ecb1d65d5a 100644 (file)
--- a/crypto/bn/bn_recp.c
+++ b/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;
+BN_RECP_CTX *recp;
+BN_CTX *ctx;
+       {
+       int ret=0;
+       BIGNUM *a;
+
+       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
+               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;
-BIGNUM *i;
-int nb;
+BN_RECP_CTX *recp;
 BN_CTX *ctx;
        {
-       int ret=0,j;
-       BIGNUM *a,*b,*c,*d;
+       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);
+               }
 
-       a=ctx->bn[ctx->tos++];
-       b=ctx->bn[ctx->tos++];
-       c=ctx->bn[ctx->tos++];
-       d=ctx->bn[ctx->tos++];
+       /* 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);
 
-       if (x == y)
-               { if (!BN_sqr(a,x,ctx)) goto err; }
+       j=recp->num_bits*2;
+       if (j > i)
+               {
+               i=j;
+               ex=0;
+               }
        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;
+               {
+               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);
        }