2 * Copyright 2002-2018 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
5 * Licensed under the OpenSSL license (the "License"). You may not use
6 * this file except in compliance with the License. You can obtain a copy
7 * in the file LICENSE in the source distribution or at
8 * https://www.openssl.org/source/license.html
11 #include <openssl/err.h>
13 #include "internal/bn_int.h"
16 #ifndef OPENSSL_NO_EC2M
18 const EC_METHOD *EC_GF2m_simple_method(void)
20 static const EC_METHOD ret = {
22 NID_X9_62_characteristic_two_field,
23 ec_GF2m_simple_group_init,
24 ec_GF2m_simple_group_finish,
25 ec_GF2m_simple_group_clear_finish,
26 ec_GF2m_simple_group_copy,
27 ec_GF2m_simple_group_set_curve,
28 ec_GF2m_simple_group_get_curve,
29 ec_GF2m_simple_group_get_degree,
30 ec_group_simple_order_bits,
31 ec_GF2m_simple_group_check_discriminant,
32 ec_GF2m_simple_point_init,
33 ec_GF2m_simple_point_finish,
34 ec_GF2m_simple_point_clear_finish,
35 ec_GF2m_simple_point_copy,
36 ec_GF2m_simple_point_set_to_infinity,
37 0 /* set_Jprojective_coordinates_GFp */ ,
38 0 /* get_Jprojective_coordinates_GFp */ ,
39 ec_GF2m_simple_point_set_affine_coordinates,
40 ec_GF2m_simple_point_get_affine_coordinates,
44 ec_GF2m_simple_invert,
45 ec_GF2m_simple_is_at_infinity,
46 ec_GF2m_simple_is_on_curve,
48 ec_GF2m_simple_make_affine,
49 ec_GF2m_simple_points_make_affine,
51 0 /* precompute_mul */,
52 0 /* have_precompute_mul */,
53 ec_GF2m_simple_field_mul,
54 ec_GF2m_simple_field_sqr,
55 ec_GF2m_simple_field_div,
56 0 /* field_encode */ ,
57 0 /* field_decode */ ,
58 0, /* field_set_to_one */
59 ec_key_simple_priv2oct,
60 ec_key_simple_oct2priv,
62 ec_key_simple_generate_key,
63 ec_key_simple_check_key,
64 ec_key_simple_generate_public_key,
67 ecdh_simple_compute_key,
68 0, /* field_inverse_mod_ord */
69 0, /* blind_coordinates */
79 * Initialize a GF(2^m)-based EC_GROUP structure. Note that all other members
80 * are handled by EC_GROUP_new.
82 int ec_GF2m_simple_group_init(EC_GROUP *group)
84 group->field = BN_new();
88 if (group->field == NULL || group->a == NULL || group->b == NULL) {
89 BN_free(group->field);
98 * Free a GF(2^m)-based EC_GROUP structure. Note that all other members are
99 * handled by EC_GROUP_free.
101 void ec_GF2m_simple_group_finish(EC_GROUP *group)
103 BN_free(group->field);
109 * Clear and free a GF(2^m)-based EC_GROUP structure. Note that all other
110 * members are handled by EC_GROUP_clear_free.
112 void ec_GF2m_simple_group_clear_finish(EC_GROUP *group)
114 BN_clear_free(group->field);
115 BN_clear_free(group->a);
116 BN_clear_free(group->b);
126 * Copy a GF(2^m)-based EC_GROUP structure. Note that all other members are
127 * handled by EC_GROUP_copy.
129 int ec_GF2m_simple_group_copy(EC_GROUP *dest, const EC_GROUP *src)
131 if (!BN_copy(dest->field, src->field))
133 if (!BN_copy(dest->a, src->a))
135 if (!BN_copy(dest->b, src->b))
137 dest->poly[0] = src->poly[0];
138 dest->poly[1] = src->poly[1];
139 dest->poly[2] = src->poly[2];
140 dest->poly[3] = src->poly[3];
141 dest->poly[4] = src->poly[4];
142 dest->poly[5] = src->poly[5];
143 if (bn_wexpand(dest->a, (int)(dest->poly[0] + BN_BITS2 - 1) / BN_BITS2) ==
146 if (bn_wexpand(dest->b, (int)(dest->poly[0] + BN_BITS2 - 1) / BN_BITS2) ==
149 bn_set_all_zero(dest->a);
150 bn_set_all_zero(dest->b);
154 /* Set the curve parameters of an EC_GROUP structure. */
155 int ec_GF2m_simple_group_set_curve(EC_GROUP *group,
156 const BIGNUM *p, const BIGNUM *a,
157 const BIGNUM *b, BN_CTX *ctx)
162 if (!BN_copy(group->field, p))
164 i = BN_GF2m_poly2arr(group->field, group->poly, 6) - 1;
165 if ((i != 5) && (i != 3)) {
166 ECerr(EC_F_EC_GF2M_SIMPLE_GROUP_SET_CURVE, EC_R_UNSUPPORTED_FIELD);
171 if (!BN_GF2m_mod_arr(group->a, a, group->poly))
173 if (bn_wexpand(group->a, (int)(group->poly[0] + BN_BITS2 - 1) / BN_BITS2)
176 bn_set_all_zero(group->a);
179 if (!BN_GF2m_mod_arr(group->b, b, group->poly))
181 if (bn_wexpand(group->b, (int)(group->poly[0] + BN_BITS2 - 1) / BN_BITS2)
184 bn_set_all_zero(group->b);
192 * Get the curve parameters of an EC_GROUP structure. If p, a, or b are NULL
193 * then there values will not be set but the method will return with success.
195 int ec_GF2m_simple_group_get_curve(const EC_GROUP *group, BIGNUM *p,
196 BIGNUM *a, BIGNUM *b, BN_CTX *ctx)
201 if (!BN_copy(p, group->field))
206 if (!BN_copy(a, group->a))
211 if (!BN_copy(b, group->b))
222 * Gets the degree of the field. For a curve over GF(2^m) this is the value
225 int ec_GF2m_simple_group_get_degree(const EC_GROUP *group)
227 return BN_num_bits(group->field) - 1;
231 * Checks the discriminant of the curve. y^2 + x*y = x^3 + a*x^2 + b is an
232 * elliptic curve <=> b != 0 (mod p)
234 int ec_GF2m_simple_group_check_discriminant(const EC_GROUP *group,
239 BN_CTX *new_ctx = NULL;
242 ctx = new_ctx = BN_CTX_new();
244 ECerr(EC_F_EC_GF2M_SIMPLE_GROUP_CHECK_DISCRIMINANT,
245 ERR_R_MALLOC_FAILURE);
254 if (!BN_GF2m_mod_arr(b, group->b, group->poly))
258 * check the discriminant: y^2 + x*y = x^3 + a*x^2 + b is an elliptic
259 * curve <=> b != 0 (mod p)
269 BN_CTX_free(new_ctx);
273 /* Initializes an EC_POINT. */
274 int ec_GF2m_simple_point_init(EC_POINT *point)
280 if (point->X == NULL || point->Y == NULL || point->Z == NULL) {
289 /* Frees an EC_POINT. */
290 void ec_GF2m_simple_point_finish(EC_POINT *point)
297 /* Clears and frees an EC_POINT. */
298 void ec_GF2m_simple_point_clear_finish(EC_POINT *point)
300 BN_clear_free(point->X);
301 BN_clear_free(point->Y);
302 BN_clear_free(point->Z);
307 * Copy the contents of one EC_POINT into another. Assumes dest is
310 int ec_GF2m_simple_point_copy(EC_POINT *dest, const EC_POINT *src)
312 if (!BN_copy(dest->X, src->X))
314 if (!BN_copy(dest->Y, src->Y))
316 if (!BN_copy(dest->Z, src->Z))
318 dest->Z_is_one = src->Z_is_one;
319 dest->curve_name = src->curve_name;
325 * Set an EC_POINT to the point at infinity. A point at infinity is
326 * represented by having Z=0.
328 int ec_GF2m_simple_point_set_to_infinity(const EC_GROUP *group,
337 * Set the coordinates of an EC_POINT using affine coordinates. Note that
338 * the simple implementation only uses affine coordinates.
340 int ec_GF2m_simple_point_set_affine_coordinates(const EC_GROUP *group,
343 const BIGNUM *y, BN_CTX *ctx)
346 if (x == NULL || y == NULL) {
347 ECerr(EC_F_EC_GF2M_SIMPLE_POINT_SET_AFFINE_COORDINATES,
348 ERR_R_PASSED_NULL_PARAMETER);
352 if (!BN_copy(point->X, x))
354 BN_set_negative(point->X, 0);
355 if (!BN_copy(point->Y, y))
357 BN_set_negative(point->Y, 0);
358 if (!BN_copy(point->Z, BN_value_one()))
360 BN_set_negative(point->Z, 0);
369 * Gets the affine coordinates of an EC_POINT. Note that the simple
370 * implementation only uses affine coordinates.
372 int ec_GF2m_simple_point_get_affine_coordinates(const EC_GROUP *group,
373 const EC_POINT *point,
374 BIGNUM *x, BIGNUM *y,
379 if (EC_POINT_is_at_infinity(group, point)) {
380 ECerr(EC_F_EC_GF2M_SIMPLE_POINT_GET_AFFINE_COORDINATES,
381 EC_R_POINT_AT_INFINITY);
385 if (BN_cmp(point->Z, BN_value_one())) {
386 ECerr(EC_F_EC_GF2M_SIMPLE_POINT_GET_AFFINE_COORDINATES,
387 ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
391 if (!BN_copy(x, point->X))
393 BN_set_negative(x, 0);
396 if (!BN_copy(y, point->Y))
398 BN_set_negative(y, 0);
407 * Computes a + b and stores the result in r. r could be a or b, a could be
408 * b. Uses algorithm A.10.2 of IEEE P1363.
410 int ec_GF2m_simple_add(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a,
411 const EC_POINT *b, BN_CTX *ctx)
413 BN_CTX *new_ctx = NULL;
414 BIGNUM *x0, *y0, *x1, *y1, *x2, *y2, *s, *t;
417 if (EC_POINT_is_at_infinity(group, a)) {
418 if (!EC_POINT_copy(r, b))
423 if (EC_POINT_is_at_infinity(group, b)) {
424 if (!EC_POINT_copy(r, a))
430 ctx = new_ctx = BN_CTX_new();
436 x0 = BN_CTX_get(ctx);
437 y0 = BN_CTX_get(ctx);
438 x1 = BN_CTX_get(ctx);
439 y1 = BN_CTX_get(ctx);
440 x2 = BN_CTX_get(ctx);
441 y2 = BN_CTX_get(ctx);
448 if (!BN_copy(x0, a->X))
450 if (!BN_copy(y0, a->Y))
453 if (!EC_POINT_get_affine_coordinates_GF2m(group, a, x0, y0, ctx))
457 if (!BN_copy(x1, b->X))
459 if (!BN_copy(y1, b->Y))
462 if (!EC_POINT_get_affine_coordinates_GF2m(group, b, x1, y1, ctx))
466 if (BN_GF2m_cmp(x0, x1)) {
467 if (!BN_GF2m_add(t, x0, x1))
469 if (!BN_GF2m_add(s, y0, y1))
471 if (!group->meth->field_div(group, s, s, t, ctx))
473 if (!group->meth->field_sqr(group, x2, s, ctx))
475 if (!BN_GF2m_add(x2, x2, group->a))
477 if (!BN_GF2m_add(x2, x2, s))
479 if (!BN_GF2m_add(x2, x2, t))
482 if (BN_GF2m_cmp(y0, y1) || BN_is_zero(x1)) {
483 if (!EC_POINT_set_to_infinity(group, r))
488 if (!group->meth->field_div(group, s, y1, x1, ctx))
490 if (!BN_GF2m_add(s, s, x1))
493 if (!group->meth->field_sqr(group, x2, s, ctx))
495 if (!BN_GF2m_add(x2, x2, s))
497 if (!BN_GF2m_add(x2, x2, group->a))
501 if (!BN_GF2m_add(y2, x1, x2))
503 if (!group->meth->field_mul(group, y2, y2, s, ctx))
505 if (!BN_GF2m_add(y2, y2, x2))
507 if (!BN_GF2m_add(y2, y2, y1))
510 if (!EC_POINT_set_affine_coordinates_GF2m(group, r, x2, y2, ctx))
517 BN_CTX_free(new_ctx);
522 * Computes 2 * a and stores the result in r. r could be a. Uses algorithm
523 * A.10.2 of IEEE P1363.
525 int ec_GF2m_simple_dbl(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a,
528 return ec_GF2m_simple_add(group, r, a, a, ctx);
531 int ec_GF2m_simple_invert(const EC_GROUP *group, EC_POINT *point, BN_CTX *ctx)
533 if (EC_POINT_is_at_infinity(group, point) || BN_is_zero(point->Y))
534 /* point is its own inverse */
537 if (!EC_POINT_make_affine(group, point, ctx))
539 return BN_GF2m_add(point->Y, point->X, point->Y);
542 /* Indicates whether the given point is the point at infinity. */
543 int ec_GF2m_simple_is_at_infinity(const EC_GROUP *group,
544 const EC_POINT *point)
546 return BN_is_zero(point->Z);
550 * Determines whether the given EC_POINT is an actual point on the curve defined
551 * in the EC_GROUP. A point is valid if it satisfies the Weierstrass equation:
552 * y^2 + x*y = x^3 + a*x^2 + b.
554 int ec_GF2m_simple_is_on_curve(const EC_GROUP *group, const EC_POINT *point,
558 BN_CTX *new_ctx = NULL;
560 int (*field_mul) (const EC_GROUP *, BIGNUM *, const BIGNUM *,
561 const BIGNUM *, BN_CTX *);
562 int (*field_sqr) (const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
564 if (EC_POINT_is_at_infinity(group, point))
567 field_mul = group->meth->field_mul;
568 field_sqr = group->meth->field_sqr;
570 /* only support affine coordinates */
571 if (!point->Z_is_one)
575 ctx = new_ctx = BN_CTX_new();
581 y2 = BN_CTX_get(ctx);
582 lh = BN_CTX_get(ctx);
587 * We have a curve defined by a Weierstrass equation
588 * y^2 + x*y = x^3 + a*x^2 + b.
589 * <=> x^3 + a*x^2 + x*y + b + y^2 = 0
590 * <=> ((x + a) * x + y ) * x + b + y^2 = 0
592 if (!BN_GF2m_add(lh, point->X, group->a))
594 if (!field_mul(group, lh, lh, point->X, ctx))
596 if (!BN_GF2m_add(lh, lh, point->Y))
598 if (!field_mul(group, lh, lh, point->X, ctx))
600 if (!BN_GF2m_add(lh, lh, group->b))
602 if (!field_sqr(group, y2, point->Y, ctx))
604 if (!BN_GF2m_add(lh, lh, y2))
606 ret = BN_is_zero(lh);
610 BN_CTX_free(new_ctx);
615 * Indicates whether two points are equal.
618 * 0 equal (in affine coordinates)
621 int ec_GF2m_simple_cmp(const EC_GROUP *group, const EC_POINT *a,
622 const EC_POINT *b, BN_CTX *ctx)
624 BIGNUM *aX, *aY, *bX, *bY;
625 BN_CTX *new_ctx = NULL;
628 if (EC_POINT_is_at_infinity(group, a)) {
629 return EC_POINT_is_at_infinity(group, b) ? 0 : 1;
632 if (EC_POINT_is_at_infinity(group, b))
635 if (a->Z_is_one && b->Z_is_one) {
636 return ((BN_cmp(a->X, b->X) == 0) && BN_cmp(a->Y, b->Y) == 0) ? 0 : 1;
640 ctx = new_ctx = BN_CTX_new();
646 aX = BN_CTX_get(ctx);
647 aY = BN_CTX_get(ctx);
648 bX = BN_CTX_get(ctx);
649 bY = BN_CTX_get(ctx);
653 if (!EC_POINT_get_affine_coordinates_GF2m(group, a, aX, aY, ctx))
655 if (!EC_POINT_get_affine_coordinates_GF2m(group, b, bX, bY, ctx))
657 ret = ((BN_cmp(aX, bX) == 0) && BN_cmp(aY, bY) == 0) ? 0 : 1;
661 BN_CTX_free(new_ctx);
665 /* Forces the given EC_POINT to internally use affine coordinates. */
666 int ec_GF2m_simple_make_affine(const EC_GROUP *group, EC_POINT *point,
669 BN_CTX *new_ctx = NULL;
673 if (point->Z_is_one || EC_POINT_is_at_infinity(group, point))
677 ctx = new_ctx = BN_CTX_new();
688 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx))
690 if (!BN_copy(point->X, x))
692 if (!BN_copy(point->Y, y))
694 if (!BN_one(point->Z))
702 BN_CTX_free(new_ctx);
707 * Forces each of the EC_POINTs in the given array to use affine coordinates.
709 int ec_GF2m_simple_points_make_affine(const EC_GROUP *group, size_t num,
710 EC_POINT *points[], BN_CTX *ctx)
714 for (i = 0; i < num; i++) {
715 if (!group->meth->make_affine(group, points[i], ctx))
722 /* Wrapper to simple binary polynomial field multiplication implementation. */
723 int ec_GF2m_simple_field_mul(const EC_GROUP *group, BIGNUM *r,
724 const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
726 return BN_GF2m_mod_mul_arr(r, a, b, group->poly, ctx);
729 /* Wrapper to simple binary polynomial field squaring implementation. */
730 int ec_GF2m_simple_field_sqr(const EC_GROUP *group, BIGNUM *r,
731 const BIGNUM *a, BN_CTX *ctx)
733 return BN_GF2m_mod_sqr_arr(r, a, group->poly, ctx);
736 /* Wrapper to simple binary polynomial field division implementation. */
737 int ec_GF2m_simple_field_div(const EC_GROUP *group, BIGNUM *r,
738 const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
740 return BN_GF2m_mod_div(r, a, b, group->field, ctx);