Do BN_nist_mod_384 by the book, as cheating doesn't work. Other functions
authorAndy Polyakov <appro@openssl.org>
Wed, 9 Apr 2008 11:36:04 +0000 (11:36 +0000)
committerAndy Polyakov <appro@openssl.org>
Wed, 9 Apr 2008 11:36:04 +0000 (11:36 +0000)
will be revised too.
PR: 1593

crypto/bn/bn_nist.c

index fd15c28..6b88c5f 100644 (file)
@@ -176,10 +176,6 @@ const BIGNUM *BN_get0_nist_prime_521(void)
 static BN_ULONG _256_data[BN_NIST_256_TOP*6];
 static int _is_set_256_data = 0;
 static void _init_256_data(void);
-
-static BN_ULONG _384_data[BN_NIST_384_TOP*8];
-static int _is_set_384_data = 0;
-static void _init_384_data(void);
 #endif
 
 #define BN_NIST_ADD_ONE(a)     while (!(*(a)=(*(a)+1)&BN_MASK2)) ++(a);
@@ -527,26 +523,6 @@ int BN_nist_mod_256(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
 #endif
        }
 
-#if BN_BITS2 == 32
-static void _init_384_data(void)
-       {
-       int     i;
-       BN_ULONG *tmp1 = _384_data;
-       const BN_ULONG *tmp2 = tmp1;
-
-       memcpy(tmp1, _nist_p_384, BN_NIST_384_TOP * sizeof(BN_ULONG));
-       tmp1 += BN_NIST_384_TOP;
-
-       for (i=0; i<7; i++)
-               {
-               bn_add_words(tmp1, _nist_p_384, tmp2, BN_NIST_384_TOP);
-               tmp2  = tmp1;
-               tmp1 += BN_NIST_384_TOP;
-               }
-       _is_set_384_data = 1;
-       }
-#endif
-
 #define nist_set_384(to,from,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12) \
        { \
        if (a12 != 0) bn_cp_32(to, 0, from,  (a12) - 12) else bn_32_set_0(to, 0)\
@@ -571,17 +547,10 @@ int BN_nist_mod_384(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
        int     carry = 0;
        register BN_ULONG *r_d, *a_d = a->d;
        BN_ULONG t_d[BN_NIST_384_TOP],
-                buf[BN_NIST_384_TOP];
-
-       if (!_is_set_384_data)
-               {
-               CRYPTO_w_lock(CRYPTO_LOCK_BN);
-               
-               if (!_is_set_384_data)
-                       _init_384_data();
-
-               CRYPTO_w_unlock(CRYPTO_LOCK_BN);
-               }
+                buf[BN_NIST_384_TOP],
+                c_d[BN_NIST_384_TOP],
+               *res;
+       size_t   mask;
 
        i = BN_ucmp(field, a);
        if (i == 0)
@@ -624,48 +593,83 @@ int BN_nist_mod_384(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
                }
        carry = bn_add_words(r_d+(128/BN_BITS2), r_d+(128/BN_BITS2), 
                t_d, BN_NIST_256_TOP);
+       /* this is equivalent to if (result >= module) */
+       mask = 0-(size_t)bn_sub_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = ~mask | (0-(size_t)carry);
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
+
        /*S2 */
-       carry += bn_add_words(r_d, r_d, buf, BN_NIST_384_TOP);
+       carry = bn_add_words(r_d, res, buf, BN_NIST_384_TOP);
+       mask = 0-(size_t)bn_sub_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = ~mask | (0-(size_t)carry);
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
+
        /*S3*/
        nist_set_384(t_d,buf,20,19,18,17,16,15,14,13,12,23,22,21);
-       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
+       carry = bn_add_words(r_d, res, t_d, BN_NIST_384_TOP);
+       mask = 0-(size_t)bn_sub_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = ~mask | (0-(size_t)carry);
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
+
        /*S4*/
        nist_set_384(t_d,buf,19,18,17,16,15,14,13,12,20,0,23,0);
-       carry += bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
+       carry = bn_add_words(r_d, res, t_d, BN_NIST_384_TOP);
+       mask = 0-(size_t)bn_sub_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = ~mask | (0-(size_t)carry);
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
+
        /*S5*/
-       nist_set_256(t_d, buf, 0, 0, 0, 0, 23-4, 22-4, 21-4, 20-4);
-       carry += bn_add_words(r_d+(128/BN_BITS2), r_d+(128/BN_BITS2), 
-               t_d, BN_NIST_256_TOP);
+       nist_set_384(t_d, buf,0,0,0,0,23,22,21,20,0,0,0,0);
+       carry = bn_add_words(r_d, res, t_d, BN_NIST_384_TOP);
+       mask = 0-(size_t)bn_sub_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = ~mask | (0-(size_t)carry);
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
+
        /*S6*/
        nist_set_384(t_d,buf,0,0,0,0,0,0,23,22,21,0,0,20);
-       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);
+       carry = bn_add_words(r_d, res, t_d, BN_NIST_384_TOP);
+       mask = 0-(size_t)bn_sub_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = ~mask | (0-(size_t)carry);
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
 
        /*D1*/
        nist_set_384(t_d,buf,22,21,20,19,18,17,16,15,14,13,12,23);
-       carry = bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
+#if BRANCH_FREE
+       carry = bn_sub_words(r_d, res, t_d, BN_NIST_384_TOP);
+       bn_add_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = 0-(size_t)carry;
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
+#else
+       if (bn_sub_words(r_d, res, t_d, BN_NIST_384_TOP))
+               bn_add_words(r_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+#endif
        /*D2*/
        nist_set_384(t_d,buf,0,0,0,0,0,0,0,23,22,21,20,0);
-       carry += bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
+#if BRANCH_FREE
+       carry = bn_sub_words(r_d, res, t_d, BN_NIST_384_TOP);
+       bn_add_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = 0-(size_t)carry;
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
+#else
+       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP))
+               bn_add_words(r_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+#endif
        /*D3*/
        nist_set_384(t_d,buf,0,0,0,0,0,0,0,23,23,0,0,0);
-       carry += bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
-
-       if (carry)
-               bn_add_words(r_d, r_d, _384_data + BN_NIST_384_TOP *
-                               (carry-1), BN_NIST_384_TOP);
+#if BRANCH_FREE
+       carry = bn_sub_words(r_d, res, t_d, BN_NIST_384_TOP);
+       bn_add_words(c_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+       mask = 0-(size_t)carry;
+       res = (BN_ULONG *)(((size_t)c_d&mask) | ((size_t)r_d&~mask));
 
+       nist_cp_bn(r_d, res, BN_NIST_384_TOP);
+#else
+       if (bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP))
+               bn_add_words(r_d,r_d,_nist_p_384,BN_NIST_384_TOP);
+#endif
        r->top = BN_NIST_384_TOP;
        bn_correct_top(r);
-       if (BN_ucmp(r, field) >= 0)
-               {
-               bn_sub_words(r_d, r_d, _nist_p_384, BN_NIST_384_TOP);
-               bn_correct_top(r);
-               }
-       bn_check_top(r);
+
        return 1;
 #else
        return 0;