bn_recp.c 7.4 KB

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  1. /* crypto/bn/bn_recp.c */
  2. /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  3. * All rights reserved.
  4. *
  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.
  8. *
  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).
  15. *
  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.
  22. *
  23. * Redistribution and use in source and binary forms, with or without
  24. * modification, are permitted provided that the following conditions
  25. * are met:
  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)"
  40. *
  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
  51. * SUCH DAMAGE.
  52. *
  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.]
  57. */
  58. #include <stdio.h>
  59. #include "cryptlib.h"
  60. #include "bn_lcl.h"
  61. void BN_RECP_CTX_init(BN_RECP_CTX *recp)
  62. {
  63. BN_init(&(recp->N));
  64. BN_init(&(recp->Nr));
  65. recp->num_bits = 0;
  66. recp->shift = 0;
  67. recp->flags = 0;
  68. }
  69. BN_RECP_CTX *BN_RECP_CTX_new(void)
  70. {
  71. BN_RECP_CTX *ret;
  72. if ((ret = (BN_RECP_CTX *)OPENSSL_malloc(sizeof(BN_RECP_CTX))) == NULL)
  73. return (NULL);
  74. BN_RECP_CTX_init(ret);
  75. ret->flags = BN_FLG_MALLOCED;
  76. return (ret);
  77. }
  78. void BN_RECP_CTX_free(BN_RECP_CTX *recp)
  79. {
  80. if (recp == NULL)
  81. return;
  82. BN_free(&(recp->N));
  83. BN_free(&(recp->Nr));
  84. if (recp->flags & BN_FLG_MALLOCED)
  85. OPENSSL_free(recp);
  86. }
  87. int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx)
  88. {
  89. if (!BN_copy(&(recp->N), d))
  90. return 0;
  91. BN_zero(&(recp->Nr));
  92. recp->num_bits = BN_num_bits(d);
  93. recp->shift = 0;
  94. return (1);
  95. }
  96. int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y,
  97. BN_RECP_CTX *recp, BN_CTX *ctx)
  98. {
  99. int ret = 0;
  100. BIGNUM *a;
  101. const BIGNUM *ca;
  102. BN_CTX_start(ctx);
  103. if ((a = BN_CTX_get(ctx)) == NULL)
  104. goto err;
  105. if (y != NULL) {
  106. if (x == y) {
  107. if (!BN_sqr(a, x, ctx))
  108. goto err;
  109. } else {
  110. if (!BN_mul(a, x, y, ctx))
  111. goto err;
  112. }
  113. ca = a;
  114. } else
  115. ca = x; /* Just do the mod */
  116. ret = BN_div_recp(NULL, r, ca, recp, ctx);
  117. err:
  118. BN_CTX_end(ctx);
  119. bn_check_top(r);
  120. return (ret);
  121. }
  122. int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m,
  123. BN_RECP_CTX *recp, BN_CTX *ctx)
  124. {
  125. int i, j, ret = 0;
  126. BIGNUM *a, *b, *d, *r;
  127. BN_CTX_start(ctx);
  128. a = BN_CTX_get(ctx);
  129. b = BN_CTX_get(ctx);
  130. if (dv != NULL)
  131. d = dv;
  132. else
  133. d = BN_CTX_get(ctx);
  134. if (rem != NULL)
  135. r = rem;
  136. else
  137. r = BN_CTX_get(ctx);
  138. if (a == NULL || b == NULL || d == NULL || r == NULL)
  139. goto err;
  140. if (BN_ucmp(m, &(recp->N)) < 0) {
  141. BN_zero(d);
  142. if (!BN_copy(r, m)) {
  143. BN_CTX_end(ctx);
  144. return 0;
  145. }
  146. BN_CTX_end(ctx);
  147. return (1);
  148. }
  149. /*
  150. * We want the remainder Given input of ABCDEF / ab we need multiply
  151. * ABCDEF by 3 digests of the reciprocal of ab
  152. */
  153. /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */
  154. i = BN_num_bits(m);
  155. j = recp->num_bits << 1;
  156. if (j > i)
  157. i = j;
  158. /* Nr := round(2^i / N) */
  159. if (i != recp->shift)
  160. recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx);
  161. /* BN_reciprocal could have returned -1 for an error */
  162. if (recp->shift == -1)
  163. goto err;
  164. /*-
  165. * d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))|
  166. * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))|
  167. * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)|
  168. * = |m/N|
  169. */
  170. if (!BN_rshift(a, m, recp->num_bits))
  171. goto err;
  172. if (!BN_mul(b, a, &(recp->Nr), ctx))
  173. goto err;
  174. if (!BN_rshift(d, b, i - recp->num_bits))
  175. goto err;
  176. d->neg = 0;
  177. if (!BN_mul(b, &(recp->N), d, ctx))
  178. goto err;
  179. if (!BN_usub(r, m, b))
  180. goto err;
  181. r->neg = 0;
  182. #if 1
  183. j = 0;
  184. while (BN_ucmp(r, &(recp->N)) >= 0) {
  185. if (j++ > 2) {
  186. BNerr(BN_F_BN_DIV_RECP, BN_R_BAD_RECIPROCAL);
  187. goto err;
  188. }
  189. if (!BN_usub(r, r, &(recp->N)))
  190. goto err;
  191. if (!BN_add_word(d, 1))
  192. goto err;
  193. }
  194. #endif
  195. r->neg = BN_is_zero(r) ? 0 : m->neg;
  196. d->neg = m->neg ^ recp->N.neg;
  197. ret = 1;
  198. err:
  199. BN_CTX_end(ctx);
  200. bn_check_top(dv);
  201. bn_check_top(rem);
  202. return (ret);
  203. }
  204. /*
  205. * len is the expected size of the result We actually calculate with an extra
  206. * word of precision, so we can do faster division if the remainder is not
  207. * required.
  208. */
  209. /* r := 2^len / m */
  210. int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx)
  211. {
  212. int ret = -1;
  213. BIGNUM *t;
  214. BN_CTX_start(ctx);
  215. if ((t = BN_CTX_get(ctx)) == NULL)
  216. goto err;
  217. if (!BN_set_bit(t, len))
  218. goto err;
  219. if (!BN_div(r, NULL, t, m, ctx))
  220. goto err;
  221. ret = len;
  222. err:
  223. bn_check_top(r);
  224. BN_CTX_end(ctx);
  225. return (ret);
  226. }