Fix fast reduction on NIST curves (as well BN_NIST_ADD_ONE macro).
authorAndy Polyakov <appro@openssl.org>
Tue, 1 Apr 2008 08:39:08 +0000 (08:39 +0000)
committerAndy Polyakov <appro@openssl.org>
Tue, 1 Apr 2008 08:39:08 +0000 (08:39 +0000)
PR: 1593

crypto/bn/bn_nist.c

index f8e306b..fd15c28 100644 (file)
@@ -182,7 +182,7 @@ static int _is_set_384_data = 0;
 static void _init_384_data(void);
 #endif
 
-#define BN_NIST_ADD_ONE(a)     while (!(++(*(a)))) ++(a);
+#define BN_NIST_ADD_ONE(a)     while (!(*(a)=(*(a)+1)&BN_MASK2)) ++(a);
 
 static void nist_cp_bn_0(BN_ULONG *buf, BN_ULONG *a, int top, int max)
         {
@@ -255,7 +255,6 @@ int BN_nist_mod_192(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
        BN_CTX *ctx)
        {
        int      top = a->top, i;
-       BN_ULONG carry = 0;
        register BN_ULONG *r_d, *a_d = a->d;
        BN_ULONG t_d[BN_NIST_192_TOP],
                 buf[BN_NIST_192_TOP];
@@ -291,11 +290,11 @@ int BN_nist_mod_192(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 
        nist_set_192(t_d, buf, 0, 3, 3);
        if (bn_add_words(r_d, r_d, t_d, BN_NIST_192_TOP))
-               ++carry;
+               bn_sub_words(r_d, r_d, _nist_p_192, BN_NIST_192_TOP);
 
        nist_set_192(t_d, buf, 4, 4, 0);
        if (bn_add_words(r_d, r_d, t_d, BN_NIST_192_TOP))
-               ++carry;
+               bn_sub_words(r_d, r_d, _nist_p_192, BN_NIST_192_TOP);
 
 #if defined(OPENSSL_SYS_VMS) && defined(__DECC)
 # pragma message restore
@@ -303,13 +302,8 @@ int BN_nist_mod_192(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 
        nist_set_192(t_d, buf, 5, 5, 5)
        if (bn_add_words(r_d, r_d, t_d, BN_NIST_192_TOP))
-               ++carry;
+               bn_sub_words(r_d, r_d, _nist_p_192, BN_NIST_192_TOP);
 
-       while (carry)
-               {
-               if (bn_sub_words(r_d, r_d, _nist_p_192, BN_NIST_192_TOP))
-                       --carry; 
-               }
        r->top = BN_NIST_192_TOP;
        bn_correct_top(r);
        if (BN_ucmp(r, field) >= 0)
@@ -336,9 +330,8 @@ int BN_nist_mod_192(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 int BN_nist_mod_224(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
        BN_CTX *ctx)
        {
-#if BN_BITS2 != 64
+#if BN_BITS2 == 32
        int     top = a->top, i;
-       int     carry = 0;
        BN_ULONG *r_d, *a_d = a->d;
        BN_ULONG t_d[BN_NIST_224_TOP],
                 buf[BN_NIST_224_TOP];
@@ -369,29 +362,16 @@ int BN_nist_mod_224(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 
        nist_set_224(t_d, buf, 10, 9, 8, 7, 0, 0, 0);
        if (bn_add_words(r_d, r_d, t_d, BN_NIST_224_TOP))
-               ++carry;
+               bn_sub_words(r_d,r_d,_nist_p_224,BN_NIST_224_TOP);
        nist_set_224(t_d, buf, 0, 13, 12, 11, 0, 0, 0);
        if (bn_add_words(r_d, r_d, t_d, BN_NIST_224_TOP))
-               ++carry;
+               bn_sub_words(r_d,r_d,_nist_p_224,BN_NIST_224_TOP);
        nist_set_224(t_d, buf, 13, 12, 11, 10, 9, 8, 7);
        if (bn_sub_words(r_d, r_d, t_d, BN_NIST_224_TOP))
-               --carry;
+               bn_add_words(r_d,r_d,_nist_p_224,BN_NIST_224_TOP);
        nist_set_224(t_d, buf, 0, 0, 0, 0, 13, 12, 11);
        if (bn_sub_words(r_d, r_d, t_d, BN_NIST_224_TOP))
-               --carry;
-
-       if (carry > 0)
-               while (carry)
-                       {
-                       if (bn_sub_words(r_d,r_d,_nist_p_224,BN_NIST_224_TOP))
-                               --carry;
-                       }
-       else if (carry < 0)
-               while (carry)
-                       {
-                       if (bn_add_words(r_d,r_d,_nist_p_224,BN_NIST_224_TOP))
-                               ++carry;
-                       }
+               bn_add_words(r_d,r_d,_nist_p_224,BN_NIST_224_TOP);
 
        r->top = BN_NIST_224_TOP;
        bn_correct_top(r);
@@ -407,7 +387,7 @@ int BN_nist_mod_224(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 #endif
        }
 
-#if BN_BITS2 != 64
+#if BN_BITS2 == 32
 static void _init_256_data(void)
        {
        int     i;
@@ -442,7 +422,7 @@ static void _init_256_data(void)
 int BN_nist_mod_256(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
        BN_CTX *ctx)
        {
-#if BN_BITS2 != 64
+#if BN_BITS2 == 32
        int     i, top = a->top;
        int     carry = 0;
        register BN_ULONG *a_d = a->d, *r_d;
@@ -488,8 +468,7 @@ int BN_nist_mod_256(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
        nist_set_256(t_d, buf, 15, 14, 13, 12, 11, 0, 0, 0);
        /*S2*/
        nist_set_256(t_d2,buf, 0, 15, 14, 13, 12, 0, 0, 0);
-       if (bn_add_words(t_d, t_d, t_d2, BN_NIST_256_TOP))
-               carry = 2;
+       carry = bn_add_words(t_d, t_d, t_d2, BN_NIST_256_TOP);
        /* left shift */
                {
                register BN_ULONG *ap,t,c;
@@ -501,49 +480,38 @@ int BN_nist_mod_256(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
                        *(ap++)=((t<<1)|c)&BN_MASK2;
                        c=(t & BN_TBIT)?1:0;
                        }
-               if (c)
-                       ++carry;
+               carry <<= 1;
+               carry  |= c;
                }
 
-       if (bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP))
-               ++carry;
+       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP);
        /*S3*/
        nist_set_256(t_d, buf, 15, 14, 0, 0, 0, 10, 9, 8);
-       if (bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP))
-               ++carry;
+       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP);
        /*S4*/
        nist_set_256(t_d, buf, 8, 13, 15, 14, 13, 11, 10, 9);
-       if (bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP))
-               ++carry;
+       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP);
+
+       if (carry)
+               bn_sub_words(r_d, r_d, _256_data + BN_NIST_256_TOP *
+                               (carry-1), BN_NIST_256_TOP);
+
        /*D1*/
        nist_set_256(t_d, buf, 10, 8, 0, 0, 0, 13, 12, 11);
-       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP))
-               --carry;
+       carry = bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);
        /*D2*/
        nist_set_256(t_d, buf, 11, 9, 0, 0, 15, 14, 13, 12);
-       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP))
-               --carry;
+       carry += bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);
        /*D3*/
        nist_set_256(t_d, buf, 12, 0, 10, 9, 8, 15, 14, 13);
-       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP))
-               --carry;
+       carry += bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);
        /*D4*/
        nist_set_256(t_d, buf, 13, 0, 11, 10, 9, 0, 15, 14);
-       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP))
-               --carry;
+       carry += bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);
        
        if (carry)
-               {
-               if (carry > 0)
-                       bn_sub_words(r_d, r_d, _256_data + BN_NIST_256_TOP *
-                               --carry, BN_NIST_256_TOP);
-               else
-                       {
-                       carry = -carry;
-                       bn_add_words(r_d, r_d, _256_data + BN_NIST_256_TOP *
-                               --carry, BN_NIST_256_TOP);
-                       }
-               }
+               bn_add_words(r_d, r_d, _256_data + BN_NIST_256_TOP *
+                               (carry-1), BN_NIST_256_TOP);
 
        r->top = BN_NIST_256_TOP;
        bn_correct_top(r);
@@ -559,7 +527,7 @@ int BN_nist_mod_256(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 #endif
        }
 
-#if BN_BITS2 != 64
+#if BN_BITS2 == 32
 static void _init_384_data(void)
        {
        int     i;
@@ -598,7 +566,7 @@ static void _init_384_data(void)
 int BN_nist_mod_384(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
        BN_CTX *ctx)
        {
-#if BN_BITS2 != 64
+#if BN_BITS2 == 32
        int     i, top = a->top;
        int     carry = 0;
        register BN_ULONG *r_d, *a_d = a->d;
@@ -646,61 +614,49 @@ int BN_nist_mod_384(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
                register BN_ULONG *ap,t,c;
                ap = t_d;
                c=0;
-               for (i = BN_NIST_256_TOP; i != 0; --i)
+               for (i = 3; i != 0; --i)
                        {
                        t= *ap;
                        *(ap++)=((t<<1)|c)&BN_MASK2;
                        c=(t & BN_TBIT)?1:0;
                        }
+               *ap=c;
                }
-       if (bn_add_words(r_d+(128/BN_BITS2), r_d+(128/BN_BITS2), 
-               t_d, BN_NIST_256_TOP))
-               ++carry;
+       carry = bn_add_words(r_d+(128/BN_BITS2), r_d+(128/BN_BITS2), 
+               t_d, BN_NIST_256_TOP);
        /*S2 */
-       if (bn_add_words(r_d, r_d, buf, BN_NIST_384_TOP))
-               ++carry;
+       carry += bn_add_words(r_d, r_d, buf, BN_NIST_384_TOP);
        /*S3*/
        nist_set_384(t_d,buf,20,19,18,17,16,15,14,13,12,23,22,21);
-       if (bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP))
-               ++carry;
+       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
        /*S4*/
        nist_set_384(t_d,buf,19,18,17,16,15,14,13,12,20,0,23,0);
-       if (bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP))
-               ++carry;
+       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
        /*S5*/
        nist_set_256(t_d, buf, 0, 0, 0, 0, 23-4, 22-4, 21-4, 20-4);
-       if (bn_add_words(r_d+(128/BN_BITS2), r_d+(128/BN_BITS2), 
-               t_d, BN_NIST_256_TOP))
-               ++carry;
+       carry += bn_add_words(r_d+(128/BN_BITS2), r_d+(128/BN_BITS2), 
+               t_d, BN_NIST_256_TOP);
        /*S6*/
        nist_set_384(t_d,buf,0,0,0,0,0,0,23,22,21,0,0,20);
-       if (bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP))
-               ++carry;
+       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
+
+       if (carry)
+               bn_sub_words(r_d, r_d, _384_data + BN_NIST_384_TOP *
+                               (carry-1), BN_NIST_384_TOP);
+
        /*D1*/
        nist_set_384(t_d,buf,22,21,20,19,18,17,16,15,14,13,12,23);
-       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP))
-               --carry;
+       carry = bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
        /*D2*/
        nist_set_384(t_d,buf,0,0,0,0,0,0,0,23,22,21,20,0);
-       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP))
-               --carry;
+       carry += bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
        /*D3*/
        nist_set_384(t_d,buf,0,0,0,0,0,0,0,23,23,0,0,0);
-       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP))
-               --carry;
-       
+       carry += bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
+
        if (carry)
-               {
-               if (carry > 0)
-                       bn_sub_words(r_d, r_d, _384_data + BN_NIST_384_TOP *
-                               --carry, BN_NIST_384_TOP);
-               else
-                       {
-                       carry = -carry;
-                       bn_add_words(r_d, r_d, _384_data + BN_NIST_384_TOP *
-                               --carry, BN_NIST_384_TOP);
-                       }
-               }
+               bn_add_words(r_d, r_d, _384_data + BN_NIST_384_TOP *
+                               (carry-1), BN_NIST_384_TOP);
 
        r->top = BN_NIST_384_TOP;
        bn_correct_top(r);
@@ -762,7 +718,7 @@ int BN_nist_mod_521(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
            (r_d[BN_NIST_521_TOP-1] & ~(BN_NIST_521_TOP_MASK)))
                {
                BN_NIST_ADD_ONE(r_d)
-               r_d[BN_NIST_521_TOP-1] &= BN_NIST_521_TOP_MASK; 
+               r->d[BN_NIST_521_TOP-1] &= BN_NIST_521_TOP_MASK; 
                }
        bn_correct_top(r);