1  /*
 2   *  Copyright (C) 2017 - 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   *      Jean-Pierre FLORI <jean-pierre.flori@ssi.gouv.fr>
 8   *
 9   *  Contributors:
10   *      Nicolas VIVET <nicolas.vivet@ssi.gouv.fr>
11   *      Karim KHALFALLAH <karim.khalfallah@ssi.gouv.fr>
12   *
13   *  This software is licensed under a dual BSD and GPL v2 license.
14   *  See LICENSE file at the root folder of the project.
15   */
16  #include <libecc/curves/ec_edwards.h>
17  
18  #define EC_EDWARDS_CRV_MAGIC ((word_t)(0x9c7349a1837c6794ULL))
19  
20  /*
21   * Check pointed Edwards curve structure has already been
22   * initialized.
23   *
24   * Returns 0 on success, -1 on error.
25   */
26  int ec_edwards_crv_check_initialized(ec_edwards_crv_src_t crv)
27  {
28  	int ret;
29  
30  	MUST_HAVE((crv != NULL) && (crv->magic == EC_EDWARDS_CRV_MAGIC), ret, err);
31  	ret = 0;
32  
33  err:
34  	return ret;
35  }
36  
37  /*
38   * Initialize pointed Edwards curve structure using given a and d
39   * Fp elements representing curve equation (a x^2 + y^2 = 1 + d x^2 y^2) parameters.
40   *
41   * Returns 0 on success, -1 on error.
42   */
43  int ec_edwards_crv_init(ec_edwards_crv_t crv, fp_src_t a, fp_src_t d, nn_src_t order)
44  {
45  	int ret, iszero, cmp;
46  
47  	ret = nn_check_initialized(order); EG(ret, err);
48  	ret = fp_check_initialized(a); EG(ret, err);
49  	ret = fp_check_initialized(d); EG(ret, err);
50  	MUST_HAVE((a->ctx == d->ctx), ret, err);
51  	MUST_HAVE((crv != NULL), ret, err);
52  
53  	/* a and d in Fp, must be distinct and non zero */
54  	MUST_HAVE((!fp_iszero(a, &iszero)) && (!iszero), ret, err);
55  	MUST_HAVE((!fp_iszero(d, &iszero)) && (!iszero), ret, err);
56  	MUST_HAVE((!fp_cmp(a, d, &cmp)) && cmp, ret, err);
57  
58  	ret = fp_init(&(crv->a), a->ctx); EG(ret, err);
59  	ret = fp_init(&(crv->d), d->ctx); EG(ret, err);
60  	ret = fp_copy(&(crv->a), a); EG(ret, err);
61  	ret = fp_copy(&(crv->d), d); EG(ret, err);
62  	ret = nn_copy(&(crv->order), order); EG(ret, err);
63  
64  	crv->magic = EC_EDWARDS_CRV_MAGIC;
65  
66  err:
67  	return ret;
68  }
69  
70  
71  /* Uninitialize curve */
72  void ec_edwards_crv_uninit(ec_edwards_crv_t crv)
73  {
74  	if ((crv != NULL) && (crv->magic == EC_EDWARDS_CRV_MAGIC)) {
75  		crv->magic = WORD(0);
76  	}
77  
78  	return;
79  }