1 /*
2 * Copyright (C) 2021 - This file is part of libecc project
3 *
4 * Authors:
5 * Ryad BENADJILA <ryadbenadjila@gmail.com>
6 * Arnaud EBALARD <arnaud.ebalard@ssi.gouv.fr>
7 *
8 * This software is licensed under a dual BSD and GPL v2 license.
9 * See LICENSE file at the root folder of the project.
10 */
11 #include <libecc/curves/ec_montgomery.h>
12
13 #define EC_MONTGOMERY_CRV_MAGIC ((word_t)(0x83734673a0443720ULL))
14
15 /* Check if a Montgomery curve is initialized.
16 * Returns 0 on success, -1 on error.
17 */
ec_montgomery_crv_check_initialized(ec_montgomery_crv_src_t crv)18 int ec_montgomery_crv_check_initialized(ec_montgomery_crv_src_t crv)
19 {
20 int ret;
21
22 MUST_HAVE((crv != NULL) && (crv->magic == EC_MONTGOMERY_CRV_MAGIC), ret, err);
23 ret = 0;
24
25 err:
26 return ret;
27 }
28
29 /*
30 * Initialize pointed Montgomery curve structure using given A and B
31 * Fp elements representing curve equation (B v^2 = u^3 + A u^2 + u) parameters.
32 *
33 * The function returns 0 on success, -1 on error.
34 */
ec_montgomery_crv_init(ec_montgomery_crv_t crv,fp_src_t A,fp_src_t B,nn_src_t order)35 int ec_montgomery_crv_init(ec_montgomery_crv_t crv, fp_src_t A, fp_src_t B, nn_src_t order)
36 {
37 int ret, iszero;
38 fp tmp;
39 tmp.magic = WORD(0);
40
41 MUST_HAVE((crv != NULL), ret, err);
42
43 ret = nn_check_initialized(order); EG(ret, err);
44 ret = fp_check_initialized(A); EG(ret, err);
45 ret = fp_check_initialized(B); EG(ret, err);
46 MUST_HAVE(A->ctx == B->ctx, ret, err);
47
48 ret = fp_init(&tmp, A->ctx); EG(ret, err);
49
50 /* A and B elements of Fp, A unequal to (+/-)2 and B non zero */
51 ret = fp_set_word_value(&tmp, 2); EG(ret, err);
52 ret = fp_add(&tmp, A, &tmp); EG(ret, err);
53 MUST_HAVE((!fp_iszero(&tmp, &iszero)) && (!iszero), ret, err);
54
55 ret = fp_set_word_value(&tmp, 2); EG(ret, err);
56 ret = fp_sub(&tmp, A, &tmp); EG(ret, err);
57 MUST_HAVE((!fp_iszero(&tmp, &iszero)) && (!iszero), ret, err);
58 MUST_HAVE((!fp_iszero(B, &iszero)) && (!iszero), ret, err);
59
60 ret = fp_init(&(crv->A), A->ctx); EG(ret, err);
61 ret = fp_init(&(crv->B), B->ctx); EG(ret, err);
62
63 ret = fp_copy(&(crv->A), A); EG(ret, err);
64 ret = fp_copy(&(crv->B), B); EG(ret, err);
65
66 ret = nn_copy(&(crv->order), order); EG(ret, err);
67
68 crv->magic = EC_MONTGOMERY_CRV_MAGIC;
69
70 err:
71 fp_uninit(&tmp);
72
73 return ret;
74 }
75
76 /* Uninitialize curve
77 */
ec_montgomery_crv_uninit(ec_montgomery_crv_t crv)78 void ec_montgomery_crv_uninit(ec_montgomery_crv_t crv)
79 {
80 if ((crv != NULL) && (crv->magic == EC_MONTGOMERY_CRV_MAGIC)) {
81 crv->magic = WORD(0);
82 }
83
84 return;
85 }
86