1 /* crypto/ec/ec2_smpl.c */
2 /* ====================================================================
3 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
4 *
5 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
6 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
7 * to the OpenSSL project.
8 *
9 * The ECC Code is licensed pursuant to the OpenSSL open source
10 * license provided below.
11 *
12 * The software is originally written by Sheueling Chang Shantz and
13 * Douglas Stebila of Sun Microsystems Laboratories.
14 *
15 */
16 /* ====================================================================
17 * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
18 *
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
21 * are met:
22 *
23 * 1. Redistributions of source code must retain the above copyright
24 * notice, this list of conditions and the following disclaimer.
25 *
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in
28 * the documentation and/or other materials provided with the
29 * distribution.
30 *
31 * 3. All advertising materials mentioning features or use of this
32 * software must display the following acknowledgment:
33 * "This product includes software developed by the OpenSSL Project
34 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
35 *
36 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
37 * endorse or promote products derived from this software without
38 * prior written permission. For written permission, please contact
39 * openssl-core@openssl.org.
40 *
41 * 5. Products derived from this software may not be called "OpenSSL"
42 * nor may "OpenSSL" appear in their names without prior written
43 * permission of the OpenSSL Project.
44 *
45 * 6. Redistributions of any form whatsoever must retain the following
46 * acknowledgment:
47 * "This product includes software developed by the OpenSSL Project
48 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
51 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
53 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
54 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
55 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
56 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
57 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
58 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
59 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
60 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
61 * OF THE POSSIBILITY OF SUCH DAMAGE.
62 * ====================================================================
63 *
64 * This product includes cryptographic software written by Eric Young
65 * (eay@cryptsoft.com). This product includes software written by Tim
66 * Hudson (tjh@cryptsoft.com).
67 *
68 */
69
70 #include <openssl/err.h>
71
72 #include "ec_lcl.h"
73
74 #ifndef OPENSSL_NO_EC2M
75
76 #ifdef OPENSSL_FIPS
77 #include <openssl/fips.h>
78 #endif
79
80
EC_GF2m_simple_method(void)81 const EC_METHOD *EC_GF2m_simple_method(void)
82 {
83 #ifdef OPENSSL_FIPS
84 return fips_ec_gf2m_simple_method();
85 #else
86 static const EC_METHOD ret = {
87 EC_FLAGS_DEFAULT_OCT,
88 NID_X9_62_characteristic_two_field,
89 ec_GF2m_simple_group_init,
90 ec_GF2m_simple_group_finish,
91 ec_GF2m_simple_group_clear_finish,
92 ec_GF2m_simple_group_copy,
93 ec_GF2m_simple_group_set_curve,
94 ec_GF2m_simple_group_get_curve,
95 ec_GF2m_simple_group_get_degree,
96 ec_GF2m_simple_group_check_discriminant,
97 ec_GF2m_simple_point_init,
98 ec_GF2m_simple_point_finish,
99 ec_GF2m_simple_point_clear_finish,
100 ec_GF2m_simple_point_copy,
101 ec_GF2m_simple_point_set_to_infinity,
102 0 /* set_Jprojective_coordinates_GFp */,
103 0 /* get_Jprojective_coordinates_GFp */,
104 ec_GF2m_simple_point_set_affine_coordinates,
105 ec_GF2m_simple_point_get_affine_coordinates,
106 0,0,0,
107 ec_GF2m_simple_add,
108 ec_GF2m_simple_dbl,
109 ec_GF2m_simple_invert,
110 ec_GF2m_simple_is_at_infinity,
111 ec_GF2m_simple_is_on_curve,
112 ec_GF2m_simple_cmp,
113 ec_GF2m_simple_make_affine,
114 ec_GF2m_simple_points_make_affine,
115
116 /* the following three method functions are defined in ec2_mult.c */
117 ec_GF2m_simple_mul,
118 ec_GF2m_precompute_mult,
119 ec_GF2m_have_precompute_mult,
120
121 ec_GF2m_simple_field_mul,
122 ec_GF2m_simple_field_sqr,
123 ec_GF2m_simple_field_div,
124 0 /* field_encode */,
125 0 /* field_decode */,
126 0 /* field_set_to_one */ };
127
128 return &ret;
129 #endif
130 }
131
132
133 /* Initialize a GF(2^m)-based EC_GROUP structure.
134 * Note that all other members are handled by EC_GROUP_new.
135 */
ec_GF2m_simple_group_init(EC_GROUP * group)136 int ec_GF2m_simple_group_init(EC_GROUP *group)
137 {
138 BN_init(&group->field);
139 BN_init(&group->a);
140 BN_init(&group->b);
141 return 1;
142 }
143
144
145 /* Free a GF(2^m)-based EC_GROUP structure.
146 * Note that all other members are handled by EC_GROUP_free.
147 */
ec_GF2m_simple_group_finish(EC_GROUP * group)148 void ec_GF2m_simple_group_finish(EC_GROUP *group)
149 {
150 BN_free(&group->field);
151 BN_free(&group->a);
152 BN_free(&group->b);
153 }
154
155
156 /* Clear and free a GF(2^m)-based EC_GROUP structure.
157 * Note that all other members are handled by EC_GROUP_clear_free.
158 */
ec_GF2m_simple_group_clear_finish(EC_GROUP * group)159 void ec_GF2m_simple_group_clear_finish(EC_GROUP *group)
160 {
161 BN_clear_free(&group->field);
162 BN_clear_free(&group->a);
163 BN_clear_free(&group->b);
164 group->poly[0] = 0;
165 group->poly[1] = 0;
166 group->poly[2] = 0;
167 group->poly[3] = 0;
168 group->poly[4] = 0;
169 group->poly[5] = -1;
170 }
171
172
173 /* Copy a GF(2^m)-based EC_GROUP structure.
174 * Note that all other members are handled by EC_GROUP_copy.
175 */
ec_GF2m_simple_group_copy(EC_GROUP * dest,const EC_GROUP * src)176 int ec_GF2m_simple_group_copy(EC_GROUP *dest, const EC_GROUP *src)
177 {
178 int i;
179 if (!BN_copy(&dest->field, &src->field)) return 0;
180 if (!BN_copy(&dest->a, &src->a)) return 0;
181 if (!BN_copy(&dest->b, &src->b)) return 0;
182 dest->poly[0] = src->poly[0];
183 dest->poly[1] = src->poly[1];
184 dest->poly[2] = src->poly[2];
185 dest->poly[3] = src->poly[3];
186 dest->poly[4] = src->poly[4];
187 dest->poly[5] = src->poly[5];
188 if (bn_wexpand(&dest->a, (int)(dest->poly[0] + BN_BITS2 - 1) / BN_BITS2) == NULL) return 0;
189 if (bn_wexpand(&dest->b, (int)(dest->poly[0] + BN_BITS2 - 1) / BN_BITS2) == NULL) return 0;
190 for (i = dest->a.top; i < dest->a.dmax; i++) dest->a.d[i] = 0;
191 for (i = dest->b.top; i < dest->b.dmax; i++) dest->b.d[i] = 0;
192 return 1;
193 }
194
195
196 /* Set the curve parameters of an EC_GROUP structure. */
ec_GF2m_simple_group_set_curve(EC_GROUP * group,const BIGNUM * p,const BIGNUM * a,const BIGNUM * b,BN_CTX * ctx)197 int ec_GF2m_simple_group_set_curve(EC_GROUP *group,
198 const BIGNUM *p, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
199 {
200 int ret = 0, i;
201
202 /* group->field */
203 if (!BN_copy(&group->field, p)) goto err;
204 i = BN_GF2m_poly2arr(&group->field, group->poly, 6) - 1;
205 if ((i != 5) && (i != 3))
206 {
207 ECerr(EC_F_EC_GF2M_SIMPLE_GROUP_SET_CURVE, EC_R_UNSUPPORTED_FIELD);
208 goto err;
209 }
210
211 /* group->a */
212 if (!BN_GF2m_mod_arr(&group->a, a, group->poly)) goto err;
213 if(bn_wexpand(&group->a, (int)(group->poly[0] + BN_BITS2 - 1) / BN_BITS2) == NULL) goto err;
214 for (i = group->a.top; i < group->a.dmax; i++) group->a.d[i] = 0;
215
216 /* group->b */
217 if (!BN_GF2m_mod_arr(&group->b, b, group->poly)) goto err;
218 if(bn_wexpand(&group->b, (int)(group->poly[0] + BN_BITS2 - 1) / BN_BITS2) == NULL) goto err;
219 for (i = group->b.top; i < group->b.dmax; i++) group->b.d[i] = 0;
220
221 ret = 1;
222 err:
223 return ret;
224 }
225
226
227 /* Get the curve parameters of an EC_GROUP structure.
228 * If p, a, or b are NULL then there values will not be set but the method will return with success.
229 */
ec_GF2m_simple_group_get_curve(const EC_GROUP * group,BIGNUM * p,BIGNUM * a,BIGNUM * b,BN_CTX * ctx)230 int ec_GF2m_simple_group_get_curve(const EC_GROUP *group, BIGNUM *p, BIGNUM *a, BIGNUM *b, BN_CTX *ctx)
231 {
232 int ret = 0;
233
234 if (p != NULL)
235 {
236 if (!BN_copy(p, &group->field)) return 0;
237 }
238
239 if (a != NULL)
240 {
241 if (!BN_copy(a, &group->a)) goto err;
242 }
243
244 if (b != NULL)
245 {
246 if (!BN_copy(b, &group->b)) goto err;
247 }
248
249 ret = 1;
250
251 err:
252 return ret;
253 }
254
255
256 /* Gets the degree of the field. For a curve over GF(2^m) this is the value m. */
ec_GF2m_simple_group_get_degree(const EC_GROUP * group)257 int ec_GF2m_simple_group_get_degree(const EC_GROUP *group)
258 {
259 return BN_num_bits(&group->field)-1;
260 }
261
262
263 /* Checks the discriminant of the curve.
264 * y^2 + x*y = x^3 + a*x^2 + b is an elliptic curve <=> b != 0 (mod p)
265 */
ec_GF2m_simple_group_check_discriminant(const EC_GROUP * group,BN_CTX * ctx)266 int ec_GF2m_simple_group_check_discriminant(const EC_GROUP *group, BN_CTX *ctx)
267 {
268 int ret = 0;
269 BIGNUM *b;
270 BN_CTX *new_ctx = NULL;
271
272 if (ctx == NULL)
273 {
274 ctx = new_ctx = BN_CTX_new();
275 if (ctx == NULL)
276 {
277 ECerr(EC_F_EC_GF2M_SIMPLE_GROUP_CHECK_DISCRIMINANT, ERR_R_MALLOC_FAILURE);
278 goto err;
279 }
280 }
281 BN_CTX_start(ctx);
282 b = BN_CTX_get(ctx);
283 if (b == NULL) goto err;
284
285 if (!BN_GF2m_mod_arr(b, &group->b, group->poly)) goto err;
286
287 /* check the discriminant:
288 * y^2 + x*y = x^3 + a*x^2 + b is an elliptic curve <=> b != 0 (mod p)
289 */
290 if (BN_is_zero(b)) goto err;
291
292 ret = 1;
293
294 err:
295 if (ctx != NULL)
296 BN_CTX_end(ctx);
297 if (new_ctx != NULL)
298 BN_CTX_free(new_ctx);
299 return ret;
300 }
301
302
303 /* Initializes an EC_POINT. */
ec_GF2m_simple_point_init(EC_POINT * point)304 int ec_GF2m_simple_point_init(EC_POINT *point)
305 {
306 BN_init(&point->X);
307 BN_init(&point->Y);
308 BN_init(&point->Z);
309 return 1;
310 }
311
312
313 /* Frees an EC_POINT. */
ec_GF2m_simple_point_finish(EC_POINT * point)314 void ec_GF2m_simple_point_finish(EC_POINT *point)
315 {
316 BN_free(&point->X);
317 BN_free(&point->Y);
318 BN_free(&point->Z);
319 }
320
321
322 /* Clears and frees an EC_POINT. */
ec_GF2m_simple_point_clear_finish(EC_POINT * point)323 void ec_GF2m_simple_point_clear_finish(EC_POINT *point)
324 {
325 BN_clear_free(&point->X);
326 BN_clear_free(&point->Y);
327 BN_clear_free(&point->Z);
328 point->Z_is_one = 0;
329 }
330
331
332 /* Copy the contents of one EC_POINT into another. Assumes dest is initialized. */
ec_GF2m_simple_point_copy(EC_POINT * dest,const EC_POINT * src)333 int ec_GF2m_simple_point_copy(EC_POINT *dest, const EC_POINT *src)
334 {
335 if (!BN_copy(&dest->X, &src->X)) return 0;
336 if (!BN_copy(&dest->Y, &src->Y)) return 0;
337 if (!BN_copy(&dest->Z, &src->Z)) return 0;
338 dest->Z_is_one = src->Z_is_one;
339
340 return 1;
341 }
342
343
344 /* Set an EC_POINT to the point at infinity.
345 * A point at infinity is represented by having Z=0.
346 */
ec_GF2m_simple_point_set_to_infinity(const EC_GROUP * group,EC_POINT * point)347 int ec_GF2m_simple_point_set_to_infinity(const EC_GROUP *group, EC_POINT *point)
348 {
349 point->Z_is_one = 0;
350 BN_zero(&point->Z);
351 return 1;
352 }
353
354
355 /* Set the coordinates of an EC_POINT using affine coordinates.
356 * Note that the simple implementation only uses affine coordinates.
357 */
ec_GF2m_simple_point_set_affine_coordinates(const EC_GROUP * group,EC_POINT * point,const BIGNUM * x,const BIGNUM * y,BN_CTX * ctx)358 int ec_GF2m_simple_point_set_affine_coordinates(const EC_GROUP *group, EC_POINT *point,
359 const BIGNUM *x, const BIGNUM *y, BN_CTX *ctx)
360 {
361 int ret = 0;
362 if (x == NULL || y == NULL)
363 {
364 ECerr(EC_F_EC_GF2M_SIMPLE_POINT_SET_AFFINE_COORDINATES, ERR_R_PASSED_NULL_PARAMETER);
365 return 0;
366 }
367
368 if (!BN_copy(&point->X, x)) goto err;
369 BN_set_negative(&point->X, 0);
370 if (!BN_copy(&point->Y, y)) goto err;
371 BN_set_negative(&point->Y, 0);
372 if (!BN_copy(&point->Z, BN_value_one())) goto err;
373 BN_set_negative(&point->Z, 0);
374 point->Z_is_one = 1;
375 ret = 1;
376
377 err:
378 return ret;
379 }
380
381
382 /* Gets the affine coordinates of an EC_POINT.
383 * Note that the simple implementation only uses affine coordinates.
384 */
ec_GF2m_simple_point_get_affine_coordinates(const EC_GROUP * group,const EC_POINT * point,BIGNUM * x,BIGNUM * y,BN_CTX * ctx)385 int ec_GF2m_simple_point_get_affine_coordinates(const EC_GROUP *group, const EC_POINT *point,
386 BIGNUM *x, BIGNUM *y, BN_CTX *ctx)
387 {
388 int ret = 0;
389
390 if (EC_POINT_is_at_infinity(group, point))
391 {
392 ECerr(EC_F_EC_GF2M_SIMPLE_POINT_GET_AFFINE_COORDINATES, EC_R_POINT_AT_INFINITY);
393 return 0;
394 }
395
396 if (BN_cmp(&point->Z, BN_value_one()))
397 {
398 ECerr(EC_F_EC_GF2M_SIMPLE_POINT_GET_AFFINE_COORDINATES, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
399 return 0;
400 }
401 if (x != NULL)
402 {
403 if (!BN_copy(x, &point->X)) goto err;
404 BN_set_negative(x, 0);
405 }
406 if (y != NULL)
407 {
408 if (!BN_copy(y, &point->Y)) goto err;
409 BN_set_negative(y, 0);
410 }
411 ret = 1;
412
413 err:
414 return ret;
415 }
416
417 /* Computes a + b and stores the result in r. r could be a or b, a could be b.
418 * Uses algorithm A.10.2 of IEEE P1363.
419 */
ec_GF2m_simple_add(const EC_GROUP * group,EC_POINT * r,const EC_POINT * a,const EC_POINT * b,BN_CTX * ctx)420 int ec_GF2m_simple_add(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a, const EC_POINT *b, BN_CTX *ctx)
421 {
422 BN_CTX *new_ctx = NULL;
423 BIGNUM *x0, *y0, *x1, *y1, *x2, *y2, *s, *t;
424 int ret = 0;
425
426 if (EC_POINT_is_at_infinity(group, a))
427 {
428 if (!EC_POINT_copy(r, b)) return 0;
429 return 1;
430 }
431
432 if (EC_POINT_is_at_infinity(group, b))
433 {
434 if (!EC_POINT_copy(r, a)) return 0;
435 return 1;
436 }
437
438 if (ctx == NULL)
439 {
440 ctx = new_ctx = BN_CTX_new();
441 if (ctx == NULL)
442 return 0;
443 }
444
445 BN_CTX_start(ctx);
446 x0 = BN_CTX_get(ctx);
447 y0 = BN_CTX_get(ctx);
448 x1 = BN_CTX_get(ctx);
449 y1 = BN_CTX_get(ctx);
450 x2 = BN_CTX_get(ctx);
451 y2 = BN_CTX_get(ctx);
452 s = BN_CTX_get(ctx);
453 t = BN_CTX_get(ctx);
454 if (t == NULL) goto err;
455
456 if (a->Z_is_one)
457 {
458 if (!BN_copy(x0, &a->X)) goto err;
459 if (!BN_copy(y0, &a->Y)) goto err;
460 }
461 else
462 {
463 if (!EC_POINT_get_affine_coordinates_GF2m(group, a, x0, y0, ctx)) goto err;
464 }
465 if (b->Z_is_one)
466 {
467 if (!BN_copy(x1, &b->X)) goto err;
468 if (!BN_copy(y1, &b->Y)) goto err;
469 }
470 else
471 {
472 if (!EC_POINT_get_affine_coordinates_GF2m(group, b, x1, y1, ctx)) goto err;
473 }
474
475
476 if (BN_GF2m_cmp(x0, x1))
477 {
478 if (!BN_GF2m_add(t, x0, x1)) goto err;
479 if (!BN_GF2m_add(s, y0, y1)) goto err;
480 if (!group->meth->field_div(group, s, s, t, ctx)) goto err;
481 if (!group->meth->field_sqr(group, x2, s, ctx)) goto err;
482 if (!BN_GF2m_add(x2, x2, &group->a)) goto err;
483 if (!BN_GF2m_add(x2, x2, s)) goto err;
484 if (!BN_GF2m_add(x2, x2, t)) goto err;
485 }
486 else
487 {
488 if (BN_GF2m_cmp(y0, y1) || BN_is_zero(x1))
489 {
490 if (!EC_POINT_set_to_infinity(group, r)) goto err;
491 ret = 1;
492 goto err;
493 }
494 if (!group->meth->field_div(group, s, y1, x1, ctx)) goto err;
495 if (!BN_GF2m_add(s, s, x1)) goto err;
496
497 if (!group->meth->field_sqr(group, x2, s, ctx)) goto err;
498 if (!BN_GF2m_add(x2, x2, s)) goto err;
499 if (!BN_GF2m_add(x2, x2, &group->a)) goto err;
500 }
501
502 if (!BN_GF2m_add(y2, x1, x2)) goto err;
503 if (!group->meth->field_mul(group, y2, y2, s, ctx)) goto err;
504 if (!BN_GF2m_add(y2, y2, x2)) goto err;
505 if (!BN_GF2m_add(y2, y2, y1)) goto err;
506
507 if (!EC_POINT_set_affine_coordinates_GF2m(group, r, x2, y2, ctx)) goto err;
508
509 ret = 1;
510
511 err:
512 BN_CTX_end(ctx);
513 if (new_ctx != NULL)
514 BN_CTX_free(new_ctx);
515 return ret;
516 }
517
518
519 /* Computes 2 * a and stores the result in r. r could be a.
520 * Uses algorithm A.10.2 of IEEE P1363.
521 */
ec_GF2m_simple_dbl(const EC_GROUP * group,EC_POINT * r,const EC_POINT * a,BN_CTX * ctx)522 int ec_GF2m_simple_dbl(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a, BN_CTX *ctx)
523 {
524 return ec_GF2m_simple_add(group, r, a, a, ctx);
525 }
526
527
ec_GF2m_simple_invert(const EC_GROUP * group,EC_POINT * point,BN_CTX * ctx)528 int ec_GF2m_simple_invert(const EC_GROUP *group, EC_POINT *point, BN_CTX *ctx)
529 {
530 if (EC_POINT_is_at_infinity(group, point) || BN_is_zero(&point->Y))
531 /* point is its own inverse */
532 return 1;
533
534 if (!EC_POINT_make_affine(group, point, ctx)) return 0;
535 return BN_GF2m_add(&point->Y, &point->X, &point->Y);
536 }
537
538
539 /* Indicates whether the given point is the point at infinity. */
ec_GF2m_simple_is_at_infinity(const EC_GROUP * group,const EC_POINT * point)540 int ec_GF2m_simple_is_at_infinity(const EC_GROUP *group, const EC_POINT *point)
541 {
542 return BN_is_zero(&point->Z);
543 }
544
545
546 /* Determines whether the given EC_POINT is an actual point on the curve defined
547 * in the EC_GROUP. A point is valid if it satisfies the Weierstrass equation:
548 * y^2 + x*y = x^3 + a*x^2 + b.
549 */
ec_GF2m_simple_is_on_curve(const EC_GROUP * group,const EC_POINT * point,BN_CTX * ctx)550 int ec_GF2m_simple_is_on_curve(const EC_GROUP *group, const EC_POINT *point, BN_CTX *ctx)
551 {
552 int ret = -1;
553 BN_CTX *new_ctx = NULL;
554 BIGNUM *lh, *y2;
555 int (*field_mul)(const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *, BN_CTX *);
556 int (*field_sqr)(const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
557
558 if (EC_POINT_is_at_infinity(group, point))
559 return 1;
560
561 field_mul = group->meth->field_mul;
562 field_sqr = group->meth->field_sqr;
563
564 /* only support affine coordinates */
565 if (!point->Z_is_one) return -1;
566
567 if (ctx == NULL)
568 {
569 ctx = new_ctx = BN_CTX_new();
570 if (ctx == NULL)
571 return -1;
572 }
573
574 BN_CTX_start(ctx);
575 y2 = BN_CTX_get(ctx);
576 lh = BN_CTX_get(ctx);
577 if (lh == NULL) goto err;
578
579 /* We have a curve defined by a Weierstrass equation
580 * y^2 + x*y = x^3 + a*x^2 + b.
581 * <=> x^3 + a*x^2 + x*y + b + y^2 = 0
582 * <=> ((x + a) * x + y ) * x + b + y^2 = 0
583 */
584 if (!BN_GF2m_add(lh, &point->X, &group->a)) goto err;
585 if (!field_mul(group, lh, lh, &point->X, ctx)) goto err;
586 if (!BN_GF2m_add(lh, lh, &point->Y)) goto err;
587 if (!field_mul(group, lh, lh, &point->X, ctx)) goto err;
588 if (!BN_GF2m_add(lh, lh, &group->b)) goto err;
589 if (!field_sqr(group, y2, &point->Y, ctx)) goto err;
590 if (!BN_GF2m_add(lh, lh, y2)) goto err;
591 ret = BN_is_zero(lh);
592 err:
593 if (ctx) BN_CTX_end(ctx);
594 if (new_ctx) BN_CTX_free(new_ctx);
595 return ret;
596 }
597
598
599 /* Indicates whether two points are equal.
600 * Return values:
601 * -1 error
602 * 0 equal (in affine coordinates)
603 * 1 not equal
604 */
ec_GF2m_simple_cmp(const EC_GROUP * group,const EC_POINT * a,const EC_POINT * b,BN_CTX * ctx)605 int ec_GF2m_simple_cmp(const EC_GROUP *group, const EC_POINT *a, const EC_POINT *b, BN_CTX *ctx)
606 {
607 BIGNUM *aX, *aY, *bX, *bY;
608 BN_CTX *new_ctx = NULL;
609 int ret = -1;
610
611 if (EC_POINT_is_at_infinity(group, a))
612 {
613 return EC_POINT_is_at_infinity(group, b) ? 0 : 1;
614 }
615
616 if (EC_POINT_is_at_infinity(group, b))
617 return 1;
618
619 if (a->Z_is_one && b->Z_is_one)
620 {
621 return ((BN_cmp(&a->X, &b->X) == 0) && BN_cmp(&a->Y, &b->Y) == 0) ? 0 : 1;
622 }
623
624 if (ctx == NULL)
625 {
626 ctx = new_ctx = BN_CTX_new();
627 if (ctx == NULL)
628 return -1;
629 }
630
631 BN_CTX_start(ctx);
632 aX = BN_CTX_get(ctx);
633 aY = BN_CTX_get(ctx);
634 bX = BN_CTX_get(ctx);
635 bY = BN_CTX_get(ctx);
636 if (bY == NULL) goto err;
637
638 if (!EC_POINT_get_affine_coordinates_GF2m(group, a, aX, aY, ctx)) goto err;
639 if (!EC_POINT_get_affine_coordinates_GF2m(group, b, bX, bY, ctx)) goto err;
640 ret = ((BN_cmp(aX, bX) == 0) && BN_cmp(aY, bY) == 0) ? 0 : 1;
641
642 err:
643 if (ctx) BN_CTX_end(ctx);
644 if (new_ctx) BN_CTX_free(new_ctx);
645 return ret;
646 }
647
648
649 /* Forces the given EC_POINT to internally use affine coordinates. */
ec_GF2m_simple_make_affine(const EC_GROUP * group,EC_POINT * point,BN_CTX * ctx)650 int ec_GF2m_simple_make_affine(const EC_GROUP *group, EC_POINT *point, BN_CTX *ctx)
651 {
652 BN_CTX *new_ctx = NULL;
653 BIGNUM *x, *y;
654 int ret = 0;
655
656 if (point->Z_is_one || EC_POINT_is_at_infinity(group, point))
657 return 1;
658
659 if (ctx == NULL)
660 {
661 ctx = new_ctx = BN_CTX_new();
662 if (ctx == NULL)
663 return 0;
664 }
665
666 BN_CTX_start(ctx);
667 x = BN_CTX_get(ctx);
668 y = BN_CTX_get(ctx);
669 if (y == NULL) goto err;
670
671 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx)) goto err;
672 if (!BN_copy(&point->X, x)) goto err;
673 if (!BN_copy(&point->Y, y)) goto err;
674 if (!BN_one(&point->Z)) goto err;
675
676 ret = 1;
677
678 err:
679 if (ctx) BN_CTX_end(ctx);
680 if (new_ctx) BN_CTX_free(new_ctx);
681 return ret;
682 }
683
684
685 /* Forces each of the EC_POINTs in the given array to use affine coordinates. */
ec_GF2m_simple_points_make_affine(const EC_GROUP * group,size_t num,EC_POINT * points[],BN_CTX * ctx)686 int ec_GF2m_simple_points_make_affine(const EC_GROUP *group, size_t num, EC_POINT *points[], BN_CTX *ctx)
687 {
688 size_t i;
689
690 for (i = 0; i < num; i++)
691 {
692 if (!group->meth->make_affine(group, points[i], ctx)) return 0;
693 }
694
695 return 1;
696 }
697
698
699 /* Wrapper to simple binary polynomial field multiplication implementation. */
ec_GF2m_simple_field_mul(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,const BIGNUM * b,BN_CTX * ctx)700 int ec_GF2m_simple_field_mul(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
701 {
702 return BN_GF2m_mod_mul_arr(r, a, b, group->poly, ctx);
703 }
704
705
706 /* Wrapper to simple binary polynomial field squaring implementation. */
ec_GF2m_simple_field_sqr(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)707 int ec_GF2m_simple_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
708 {
709 return BN_GF2m_mod_sqr_arr(r, a, group->poly, ctx);
710 }
711
712
713 /* Wrapper to simple binary polynomial field division implementation. */
ec_GF2m_simple_field_div(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,const BIGNUM * b,BN_CTX * ctx)714 int ec_GF2m_simple_field_div(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
715 {
716 return BN_GF2m_mod_div(r, a, b, &group->field, ctx);
717 }
718
719 #endif
720