1 /* crypto/bn/bn_gcd.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
58 /* ====================================================================
59 * Copyright (c) 1998-2001 The OpenSSL Project. All rights reserved.
61 * Redistribution and use in source and binary forms, with or without
62 * modification, are permitted provided that the following conditions
65 * 1. Redistributions of source code must retain the above copyright
66 * notice, this list of conditions and the following disclaimer.
68 * 2. Redistributions in binary form must reproduce the above copyright
69 * notice, this list of conditions and the following disclaimer in
70 * the documentation and/or other materials provided with the
73 * 3. All advertising materials mentioning features or use of this
74 * software must display the following acknowledgment:
75 * "This product includes software developed by the OpenSSL Project
76 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
78 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
79 * endorse or promote products derived from this software without
80 * prior written permission. For written permission, please contact
81 * openssl-core@openssl.org.
83 * 5. Products derived from this software may not be called "OpenSSL"
84 * nor may "OpenSSL" appear in their names without prior written
85 * permission of the OpenSSL Project.
87 * 6. Redistributions of any form whatsoever must retain the following
89 * "This product includes software developed by the OpenSSL Project
90 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
92 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
93 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
94 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
95 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
96 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
97 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
98 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
99 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
100 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
101 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
102 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
103 * OF THE POSSIBILITY OF SUCH DAMAGE.
104 * ====================================================================
106 * This product includes cryptographic software written by Eric Young
107 * (eay@cryptsoft.com). This product includes software written by Tim
108 * Hudson (tjh@cryptsoft.com).
112 #define OPENSSL_FIPSAPI
114 #include "cryptlib.h"
117 static BIGNUM *euclid(BIGNUM *a, BIGNUM *b);
119 int BN_gcd(BIGNUM *r, const BIGNUM *in_a, const BIGNUM *in_b, BN_CTX *ctx)
130 if (a == NULL || b == NULL) goto err;
132 if (BN_copy(a,in_a) == NULL) goto err;
133 if (BN_copy(b,in_b) == NULL) goto err;
137 if (BN_cmp(a,b) < 0) { t=a; a=b; b=t; }
139 if (t == NULL) goto err;
141 if (BN_copy(r,t) == NULL) goto err;
149 static BIGNUM *euclid(BIGNUM *a, BIGNUM *b)
158 while (!BN_is_zero(b))
166 if (!BN_sub(a,a,b)) goto err;
167 if (!BN_rshift1(a,a)) goto err;
171 else /* a odd - b even */
173 if (!BN_rshift1(b,b)) goto err;
182 if (!BN_rshift1(a,a)) goto err;
186 else /* a even - b even */
188 if (!BN_rshift1(a,a)) goto err;
189 if (!BN_rshift1(b,b)) goto err;
198 if (!BN_lshift(a,a,shifts)) goto err;
207 /* solves ax == 1 (mod n) */
208 static BIGNUM *BN_mod_inverse_no_branch(BIGNUM *in,
209 const BIGNUM *a, const BIGNUM *n, BN_CTX *ctx);
211 BIGNUM *BN_mod_inverse(BIGNUM *in,
212 const BIGNUM *a, const BIGNUM *n, BN_CTX *ctx)
216 rv = int_bn_mod_inverse(in, a, n, ctx, &noinv);
218 BNerr(BN_F_BN_MOD_INVERSE,BN_R_NO_INVERSE);
222 BIGNUM *int_bn_mod_inverse(BIGNUM *in,
223 const BIGNUM *a, const BIGNUM *n, BN_CTX *ctx, int *pnoinv)
225 BIGNUM *A,*B,*X,*Y,*M,*D,*T,*R=NULL;
232 if ((BN_get_flags(a, BN_FLG_CONSTTIME) != 0) || (BN_get_flags(n, BN_FLG_CONSTTIME) != 0))
234 return BN_mod_inverse_no_branch(in, a, n, ctx);
248 if (T == NULL) goto err;
254 if (R == NULL) goto err;
258 if (BN_copy(B,a) == NULL) goto err;
259 if (BN_copy(A,n) == NULL) goto err;
261 if (B->neg || (BN_ucmp(B, A) >= 0))
263 if (!BN_nnmod(B, B, A, ctx)) goto err;
266 /* From B = a mod |n|, A = |n| it follows that
269 * -sign*X*a == B (mod |n|),
270 * sign*Y*a == A (mod |n|).
273 if (BN_is_odd(n) && (BN_num_bits(n) <= (BN_BITS <= 32 ? 450 : 2048)))
275 /* Binary inversion algorithm; requires odd modulus.
276 * This is faster than the general algorithm if the modulus
277 * is sufficiently small (about 400 .. 500 bits on 32-bit
278 * sytems, but much more on 64-bit systems) */
281 while (!BN_is_zero(B))
286 * (1) -sign*X*a == B (mod |n|),
287 * (2) sign*Y*a == A (mod |n|)
290 /* Now divide B by the maximum possible power of two in the integers,
291 * and divide X by the same value mod |n|.
292 * When we're done, (1) still holds. */
294 while (!BN_is_bit_set(B, shift)) /* note that 0 < B */
300 if (!BN_uadd(X, X, n)) goto err;
302 /* now X is even, so we can easily divide it by two */
303 if (!BN_rshift1(X, X)) goto err;
307 if (!BN_rshift(B, B, shift)) goto err;
311 /* Same for A and Y. Afterwards, (2) still holds. */
313 while (!BN_is_bit_set(A, shift)) /* note that 0 < A */
319 if (!BN_uadd(Y, Y, n)) goto err;
322 if (!BN_rshift1(Y, Y)) goto err;
326 if (!BN_rshift(A, A, shift)) goto err;
330 /* We still have (1) and (2).
331 * Both A and B are odd.
332 * The following computations ensure that
336 * (1) -sign*X*a == B (mod |n|),
337 * (2) sign*Y*a == A (mod |n|),
339 * and that either A or B is even in the next iteration.
341 if (BN_ucmp(B, A) >= 0)
343 /* -sign*(X + Y)*a == B - A (mod |n|) */
344 if (!BN_uadd(X, X, Y)) goto err;
345 /* NB: we could use BN_mod_add_quick(X, X, Y, n), but that
346 * actually makes the algorithm slower */
347 if (!BN_usub(B, B, A)) goto err;
351 /* sign*(X + Y)*a == A - B (mod |n|) */
352 if (!BN_uadd(Y, Y, X)) goto err;
353 /* as above, BN_mod_add_quick(Y, Y, X, n) would slow things down */
354 if (!BN_usub(A, A, B)) goto err;
360 /* general inversion algorithm */
362 while (!BN_is_zero(B))
368 * (*) -sign*X*a == B (mod |n|),
369 * sign*Y*a == A (mod |n|)
372 /* (D, M) := (A/B, A%B) ... */
373 if (BN_num_bits(A) == BN_num_bits(B))
375 if (!BN_one(D)) goto err;
376 if (!BN_sub(M,A,B)) goto err;
378 else if (BN_num_bits(A) == BN_num_bits(B) + 1)
380 /* A/B is 1, 2, or 3 */
381 if (!BN_lshift1(T,B)) goto err;
382 if (BN_ucmp(A,T) < 0)
384 /* A < 2*B, so D=1 */
385 if (!BN_one(D)) goto err;
386 if (!BN_sub(M,A,B)) goto err;
390 /* A >= 2*B, so D=2 or D=3 */
391 if (!BN_sub(M,A,T)) goto err;
392 if (!BN_add(D,T,B)) goto err; /* use D (:= 3*B) as temp */
393 if (BN_ucmp(A,D) < 0)
395 /* A < 3*B, so D=2 */
396 if (!BN_set_word(D,2)) goto err;
397 /* M (= A - 2*B) already has the correct value */
401 /* only D=3 remains */
402 if (!BN_set_word(D,3)) goto err;
403 /* currently M = A - 2*B, but we need M = A - 3*B */
404 if (!BN_sub(M,M,B)) goto err;
410 if (!BN_div(D,M,A,B,ctx)) goto err;
416 * (**) sign*Y*a == D*B + M (mod |n|).
419 tmp=A; /* keep the BIGNUM object, the value does not matter */
421 /* (A, B) := (B, A mod B) ... */
424 /* ... so we have 0 <= B < A again */
426 /* Since the former M is now B and the former B is now A,
427 * (**) translates into
428 * sign*Y*a == D*A + B (mod |n|),
430 * sign*Y*a - D*A == B (mod |n|).
431 * Similarly, (*) translates into
432 * -sign*X*a == A (mod |n|).
435 * sign*Y*a + D*sign*X*a == B (mod |n|),
437 * sign*(Y + D*X)*a == B (mod |n|).
439 * So if we set (X, Y, sign) := (Y + D*X, X, -sign), we arrive back at
440 * -sign*X*a == B (mod |n|),
441 * sign*Y*a == A (mod |n|).
442 * Note that X and Y stay non-negative all the time.
445 /* most of the time D is very small, so we can optimize tmp := D*X+Y */
448 if (!BN_add(tmp,X,Y)) goto err;
454 if (!BN_lshift1(tmp,X)) goto err;
456 else if (BN_is_word(D,4))
458 if (!BN_lshift(tmp,X,2)) goto err;
460 else if (D->top == 1)
462 if (!BN_copy(tmp,X)) goto err;
463 if (!BN_mul_word(tmp,D->d[0])) goto err;
467 if (!BN_mul(tmp,D,X,ctx)) goto err;
469 if (!BN_add(tmp,tmp,Y)) goto err;
472 M=Y; /* keep the BIGNUM object, the value does not matter */
480 * The while loop (Euclid's algorithm) ends when
483 * sign*Y*a == A (mod |n|),
484 * where Y is non-negative.
489 if (!BN_sub(Y,n,Y)) goto err;
491 /* Now Y*a == A (mod |n|). */
496 /* Y*a == 1 (mod |n|) */
497 if (!Y->neg && BN_ucmp(Y,n) < 0)
499 if (!BN_copy(R,Y)) goto err;
503 if (!BN_nnmod(R,Y,n,ctx)) goto err;
514 if ((ret == NULL) && (in == NULL)) BN_free(R);
521 /* BN_mod_inverse_no_branch is a special version of BN_mod_inverse.
522 * It does not contain branches that may leak sensitive information.
524 static BIGNUM *BN_mod_inverse_no_branch(BIGNUM *in,
525 const BIGNUM *a, const BIGNUM *n, BN_CTX *ctx)
527 BIGNUM *A,*B,*X,*Y,*M,*D,*T,*R=NULL;
528 BIGNUM local_A, local_B;
544 if (T == NULL) goto err;
550 if (R == NULL) goto err;
554 if (BN_copy(B,a) == NULL) goto err;
555 if (BN_copy(A,n) == NULL) goto err;
558 if (B->neg || (BN_ucmp(B, A) >= 0))
560 /* Turn BN_FLG_CONSTTIME flag on, so that when BN_div is invoked,
561 * BN_div_no_branch will be called eventually.
564 BN_with_flags(pB, B, BN_FLG_CONSTTIME);
565 if (!BN_nnmod(B, pB, A, ctx)) goto err;
568 /* From B = a mod |n|, A = |n| it follows that
571 * -sign*X*a == B (mod |n|),
572 * sign*Y*a == A (mod |n|).
575 while (!BN_is_zero(B))
581 * (*) -sign*X*a == B (mod |n|),
582 * sign*Y*a == A (mod |n|)
585 /* Turn BN_FLG_CONSTTIME flag on, so that when BN_div is invoked,
586 * BN_div_no_branch will be called eventually.
589 BN_with_flags(pA, A, BN_FLG_CONSTTIME);
591 /* (D, M) := (A/B, A%B) ... */
592 if (!BN_div(D,M,pA,B,ctx)) goto err;
597 * (**) sign*Y*a == D*B + M (mod |n|).
600 tmp=A; /* keep the BIGNUM object, the value does not matter */
602 /* (A, B) := (B, A mod B) ... */
605 /* ... so we have 0 <= B < A again */
607 /* Since the former M is now B and the former B is now A,
608 * (**) translates into
609 * sign*Y*a == D*A + B (mod |n|),
611 * sign*Y*a - D*A == B (mod |n|).
612 * Similarly, (*) translates into
613 * -sign*X*a == A (mod |n|).
616 * sign*Y*a + D*sign*X*a == B (mod |n|),
618 * sign*(Y + D*X)*a == B (mod |n|).
620 * So if we set (X, Y, sign) := (Y + D*X, X, -sign), we arrive back at
621 * -sign*X*a == B (mod |n|),
622 * sign*Y*a == A (mod |n|).
623 * Note that X and Y stay non-negative all the time.
626 if (!BN_mul(tmp,D,X,ctx)) goto err;
627 if (!BN_add(tmp,tmp,Y)) goto err;
629 M=Y; /* keep the BIGNUM object, the value does not matter */
636 * The while loop (Euclid's algorithm) ends when
639 * sign*Y*a == A (mod |n|),
640 * where Y is non-negative.
645 if (!BN_sub(Y,n,Y)) goto err;
647 /* Now Y*a == A (mod |n|). */
651 /* Y*a == 1 (mod |n|) */
652 if (!Y->neg && BN_ucmp(Y,n) < 0)
654 if (!BN_copy(R,Y)) goto err;
658 if (!BN_nnmod(R,Y,n,ctx)) goto err;
663 BNerr(BN_F_BN_MOD_INVERSE_NO_BRANCH,BN_R_NO_INVERSE);
668 if ((ret == NULL) && (in == NULL)) BN_free(R);