bn_word.c 6.6 KB

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  1. /* crypto/bn/bn_word.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. BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
  62. {
  63. #ifndef BN_LLONG
  64. BN_ULONG ret = 0;
  65. #else
  66. BN_ULLONG ret = 0;
  67. #endif
  68. int i;
  69. if (w == 0)
  70. return (BN_ULONG)-1;
  71. bn_check_top(a);
  72. w &= BN_MASK2;
  73. for (i = a->top - 1; i >= 0; i--) {
  74. #ifndef BN_LLONG
  75. ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & BN_MASK2l)) % w;
  76. ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w;
  77. #else
  78. ret = (BN_ULLONG) (((ret << (BN_ULLONG) BN_BITS2) | a->d[i]) %
  79. (BN_ULLONG) w);
  80. #endif
  81. }
  82. return ((BN_ULONG)ret);
  83. }
  84. BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
  85. {
  86. BN_ULONG ret = 0;
  87. int i, j;
  88. bn_check_top(a);
  89. w &= BN_MASK2;
  90. if (!w)
  91. /* actually this an error (division by zero) */
  92. return (BN_ULONG)-1;
  93. if (a->top == 0)
  94. return 0;
  95. /* normalize input (so bn_div_words doesn't complain) */
  96. j = BN_BITS2 - BN_num_bits_word(w);
  97. w <<= j;
  98. if (!BN_lshift(a, a, j))
  99. return (BN_ULONG)-1;
  100. for (i = a->top - 1; i >= 0; i--) {
  101. BN_ULONG l, d;
  102. l = a->d[i];
  103. d = bn_div_words(ret, l, w);
  104. ret = (l - ((d * w) & BN_MASK2)) & BN_MASK2;
  105. a->d[i] = d;
  106. }
  107. if ((a->top > 0) && (a->d[a->top - 1] == 0))
  108. a->top--;
  109. ret >>= j;
  110. bn_check_top(a);
  111. return (ret);
  112. }
  113. int BN_add_word(BIGNUM *a, BN_ULONG w)
  114. {
  115. BN_ULONG l;
  116. int i;
  117. bn_check_top(a);
  118. w &= BN_MASK2;
  119. /* degenerate case: w is zero */
  120. if (!w)
  121. return 1;
  122. /* degenerate case: a is zero */
  123. if (BN_is_zero(a))
  124. return BN_set_word(a, w);
  125. /* handle 'a' when negative */
  126. if (a->neg) {
  127. a->neg = 0;
  128. i = BN_sub_word(a, w);
  129. if (!BN_is_zero(a))
  130. a->neg = !(a->neg);
  131. return (i);
  132. }
  133. for (i = 0; w != 0 && i < a->top; i++) {
  134. a->d[i] = l = (a->d[i] + w) & BN_MASK2;
  135. w = (w > l) ? 1 : 0;
  136. }
  137. if (w && i == a->top) {
  138. if (bn_wexpand(a, a->top + 1) == NULL)
  139. return 0;
  140. a->top++;
  141. a->d[i] = w;
  142. }
  143. bn_check_top(a);
  144. return (1);
  145. }
  146. int BN_sub_word(BIGNUM *a, BN_ULONG w)
  147. {
  148. int i;
  149. bn_check_top(a);
  150. w &= BN_MASK2;
  151. /* degenerate case: w is zero */
  152. if (!w)
  153. return 1;
  154. /* degenerate case: a is zero */
  155. if (BN_is_zero(a)) {
  156. i = BN_set_word(a, w);
  157. if (i != 0)
  158. BN_set_negative(a, 1);
  159. return i;
  160. }
  161. /* handle 'a' when negative */
  162. if (a->neg) {
  163. a->neg = 0;
  164. i = BN_add_word(a, w);
  165. a->neg = 1;
  166. return (i);
  167. }
  168. if ((a->top == 1) && (a->d[0] < w)) {
  169. a->d[0] = w - a->d[0];
  170. a->neg = 1;
  171. return (1);
  172. }
  173. i = 0;
  174. for (;;) {
  175. if (a->d[i] >= w) {
  176. a->d[i] -= w;
  177. break;
  178. } else {
  179. a->d[i] = (a->d[i] - w) & BN_MASK2;
  180. i++;
  181. w = 1;
  182. }
  183. }
  184. if ((a->d[i] == 0) && (i == (a->top - 1)))
  185. a->top--;
  186. bn_check_top(a);
  187. return (1);
  188. }
  189. int BN_mul_word(BIGNUM *a, BN_ULONG w)
  190. {
  191. BN_ULONG ll;
  192. bn_check_top(a);
  193. w &= BN_MASK2;
  194. if (a->top) {
  195. if (w == 0)
  196. BN_zero(a);
  197. else {
  198. ll = bn_mul_words(a->d, a->d, a->top, w);
  199. if (ll) {
  200. if (bn_wexpand(a, a->top + 1) == NULL)
  201. return (0);
  202. a->d[a->top++] = ll;
  203. }
  204. }
  205. }
  206. bn_check_top(a);
  207. return (1);
  208. }