Use MONT_WORD macro to control if the word-based or the bignum
authorUlf Möller <ulf@openssl.org>
Sat, 5 Feb 2000 18:23:05 +0000 (18:23 +0000)
committerUlf Möller <ulf@openssl.org>
Sat, 5 Feb 2000 18:23:05 +0000 (18:23 +0000)
algorithm is used.

crypto/bn/bn.h
crypto/bn/bn_mont.c
doc/crypto/BN_mod_mul_montgomery.pod

index 8ac8acd..472eb2c 100644 (file)
@@ -260,7 +260,6 @@ typedef struct bn_blinding_st
 /* Used for montgomery multiplication */
 typedef struct bn_mont_ctx_st
        {
-       int use_word;  /* 0 for word form, 1 for bignum form */
        int ri;        /* number of bits in R */
        BIGNUM RR;     /* used to convert to montgomery form */
        BIGNUM N;      /* The modulus */
index 35a30a0..7bb0b91 100644 (file)
@@ -67,6 +67,8 @@
 #include "cryptlib.h"
 #include "bn_lcl.h"
 
+#define MONT_WORD /* use the faster word-based algorithm */
+
 int BN_mod_mul_montgomery(BIGNUM *r, BIGNUM *a, BIGNUM *b,
                          BN_MONT_CTX *mont, BN_CTX *ctx)
        {
@@ -105,135 +107,123 @@ err:
        return(0);
        }
 
-#define BN_RECURSION_MONT
-
 int BN_from_montgomery(BIGNUM *ret, BIGNUM *a, BN_MONT_CTX *mont,
             BN_CTX *ctx)
        {
        int retn=0;
-       BN_CTX_start(ctx);
-
-#ifdef BN_RECURSION_MONT
-       if (mont->use_word)
-#endif
-               {
-               BIGNUM *n,*r;
-               BN_ULONG *ap,*np,*rp,n0,v,*nrp;
-               int al,nl,max,i,x,ri;
 
-               if ((r = BN_CTX_get(ctx)) == NULL) goto err;
+#ifdef MONT_WORD
+       BIGNUM *n,*r;
+       BN_ULONG *ap,*np,*rp,n0,v,*nrp;
+       int al,nl,max,i,x,ri;
 
-               if (!BN_copy(r,a)) goto err;
-               n= &(mont->N);
+       BN_CTX_start(ctx);
+       if ((r = BN_CTX_get(ctx)) == NULL) goto err;
 
-               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;
+       if (!BN_copy(r,a)) goto err;
+       n= &(mont->N);
 
-               nl=n->top;
-               if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
+       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); }
 
-               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;
+       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;
 
-               r->neg=a->neg^n->neg;
-               np=n->d;
-               rp=r->d;
-               nrp= &(r->d[nl]);
+       r->neg=a->neg^n->neg;
+       np=n->d;
+       rp=r->d;
+       nrp= &(r->d[nl]);
 
-               /* clear the top words of T */
+       /* clear the top words of T */
 #if 1
-               for (i=r->top; i<max; i++) /* memset? XXX */
-                       r->d[i]=0;
+       for (i=r->top; i<max; i++) /* memset? XXX */
+               r->d[i]=0;
 #else
-               memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG)); 
+       memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG)); 
 #endif
 
-               r->top=max;
-               n0=mont->n0;
+       r->top=max;
+       n0=mont->n0;
 
 #ifdef BN_COUNT
-printf("word BN_from_montgomery %d * %d\n",nl,nl);
+       printf("word BN_from_montgomery %d * %d\n",nl,nl);
 #endif
-               for (i=0; i<nl; i++)
+       for (i=0; i<nl; i++)
+               {
+               v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
+               nrp++;
+               rp++;
+               if (((nrp[-1]+=v)&BN_MASK2) >= v)
+                       continue;
+               else
                        {
-                       v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
-                       nrp++;
-                       rp++;
-                       if (((nrp[-1]+=v)&BN_MASK2) >= v)
-                               continue;
-                       else
-                               {
-                               if (((++nrp[0])&BN_MASK2) != 0) continue;
-                               if (((++nrp[1])&BN_MASK2) != 0) continue;
-                               for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
-                               }
+                       if (((++nrp[0])&BN_MASK2) != 0) continue;
+                       if (((++nrp[1])&BN_MASK2) != 0) continue;
+                       for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
                        }
-               bn_fix_top(r);
-
-               /* mont->ri will be a multiple of the word size */
+               }
+       bn_fix_top(r);
+       
+       /* mont->ri will be a multiple of the word size */
 #if 0
-               BN_rshift(ret,r,mont->ri);
+       BN_rshift(ret,r,mont->ri);
 #else
-               x=ri;
-               rp=ret->d;
-               ap= &(r->d[x]);
-               if (r->top < x)
-                       al=0;
-               else
-                       al=r->top-x;
-               ret->top=al;
-               al-=4;
-               for (i=0; i<al; i+=4)
-                       {
-                       BN_ULONG t1,t2,t3,t4;
-
-                       t1=ap[i+0];
-                       t2=ap[i+1];
-                       t3=ap[i+2];
-                       t4=ap[i+3];
-                       rp[i+0]=t1;
-                       rp[i+1]=t2;
-                       rp[i+2]=t3;
-                       rp[i+3]=t4;
-                       }
-               al+=4;
-               for (; i<al; i++)
-                       rp[i]=ap[i];
+       x=ri;
+       rp=ret->d;
+       ap= &(r->d[x]);
+       if (r->top < x)
+               al=0;
+       else
+               al=r->top-x;
+       ret->top=al;
+       al-=4;
+       for (i=0; i<al; i+=4)
+               {
+               BN_ULONG t1,t2,t3,t4;
+               
+               t1=ap[i+0];
+               t2=ap[i+1];
+               t3=ap[i+2];
+               t4=ap[i+3];
+               rp[i+0]=t1;
+               rp[i+1]=t2;
+               rp[i+2]=t3;
+               rp[i+3]=t4;
+               }
+       al+=4;
+       for (; i<al; i++)
+               rp[i]=ap[i];
 #endif
+#else /* !MONT_WORD */ 
+       BIGNUM *t1,*t2;
 
-               if (BN_ucmp(ret, &(mont->N)) >= 0)
-                       {
-                       BN_usub(ret,ret,&(mont->N)); /* XXX */
-                       }
-               retn=1;
-               }
-#ifdef BN_RECURSION_MONT
-       else /* bignum version */ 
+       BN_CTX_start(ctx);
+       t1 = BN_CTX_get(ctx);
+       t2 = BN_CTX_get(ctx);
+       if (t1 == NULL || t2 == NULL) goto err;
+       
+       if (!BN_copy(t1,a)) goto err;
+       BN_mask_bits(t1,mont->ri);
+
+       if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err;
+       BN_mask_bits(t2,mont->ri);
+
+       if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;
+       if (!BN_add(t2,a,t1)) goto err;
+       BN_rshift(ret,t2,mont->ri);
+#endif /* MONT_WORD */
+
+       if (BN_ucmp(ret, &(mont->N)) >= 0)
                {
-               BIGNUM *t1,*t2;
-
-               t1 = BN_CTX_get(ctx);
-               t2 = BN_CTX_get(ctx);
-               if (t1 == NULL || t2 == NULL) goto err;
-
-               if (!BN_copy(t1,a)) goto err;
-               BN_mask_bits(t1,mont->ri);
-
-               if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err;
-               BN_mask_bits(t2,mont->ri);
-
-               if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;
-               if (!BN_add(t2,a,t1)) goto err;
-               BN_rshift(ret,t2,mont->ri);
-
-               if (BN_ucmp(ret,&mont->N) >= 0)
-                       BN_usub(ret,ret,&mont->N);
-               retn=1;
+               BN_usub(ret,ret,&(mont->N));
                }
-#endif
+       retn=1;
  err:
        BN_CTX_end(ctx);
        return(retn);
@@ -253,7 +243,6 @@ BN_MONT_CTX *BN_MONT_CTX_new(void)
 
 void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
        {
-       ctx->use_word=0;
        ctx->ri=0;
        BN_init(&(ctx->RR));
        BN_init(&(ctx->N));
@@ -281,16 +270,11 @@ int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
        R= &(mont->RR);                                 /* grab RR as a temp */
        BN_copy(&(mont->N),mod);                        /* Set N */
 
-#ifdef BN_RECURSION_MONT
-       /* the word-based algorithm is faster */
-       if (mont->N.top > BN_MONT_CTX_SET_SIZE_WORD)
-#endif
+#ifdef MONT_WORD
                {
                BIGNUM tmod;
                BN_ULONG buf[2];
 
-               mont->use_word=1;
-
                mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
                BN_zero(R);
                BN_set_bit(R,BN_BITS2);                 /* R */
@@ -314,10 +298,8 @@ int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
                mont->n0=Ri.d[0];
                BN_free(&Ri);
                }
-#ifdef BN_RECURSION_MONT
-       else
+#else /* !MONT_WORD */
                { /* bignum version */
-               mont->use_word=0;
                mont->ri=BN_num_bits(mod);
                BN_zero(R);
                BN_set_bit(R,mont->ri);                 /* R = 2^ri */
@@ -349,7 +331,6 @@ BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
        BN_copy(&(to->RR),&(from->RR));
        BN_copy(&(to->N),&(from->N));
        BN_copy(&(to->Ni),&(from->Ni));
-       to->use_word=from->use_word;
        to->ri=from->ri;
        to->n0=from->n0;
        return(to);
index f237f72..0f0c137 100644 (file)
@@ -58,7 +58,6 @@ The B<BN_MONT_CTX> structure is defined as follows:
 
  typedef struct bn_mont_ctx_st
         {
-        int use_word;   /* 0 for word form, 1 for bignum form */
         int ri;         /* number of bits in R */
         BIGNUM RR;      /* R^2 (used to convert to Montgomery form) */
         BIGNUM N;       /* The modulus */