ec2_smpt.c revision 296465 
1/* crypto/ec/ec2_smpt.c */
2/*
3 * This code was originally written by Douglas Stebila
4 * <dstebila@student.math.uwaterloo.ca> for the OpenSSL project.
5 */
6/* ====================================================================
7 * Copyright (c) 1998-2002 The OpenSSL Project.  All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 *
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in
18 *    the documentation and/or other materials provided with the
19 *    distribution.
20 *
21 * 3. All advertising materials mentioning features or use of this
22 *    software must display the following acknowledgment:
23 *    "This product includes software developed by the OpenSSL Project
24 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
25 *
26 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
27 *    endorse or promote products derived from this software without
28 *    prior written permission. For written permission, please contact
29 *    openssl-core@openssl.org.
30 *
31 * 5. Products derived from this software may not be called "OpenSSL"
32 *    nor may "OpenSSL" appear in their names without prior written
33 *    permission of the OpenSSL Project.
34 *
35 * 6. Redistributions of any form whatsoever must retain the following
36 *    acknowledgment:
37 *    "This product includes software developed by the OpenSSL Project
38 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
41 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
43 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
44 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
45 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
46 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
47 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
49 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
50 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
51 * OF THE POSSIBILITY OF SUCH DAMAGE.
52 * ====================================================================
53 *
54 * This product includes cryptographic software written by Eric Young
55 * (eay@cryptsoft.com).  This product includes software written by Tim
56 * Hudson (tjh@cryptsoft.com).
57 *
58 */
59
60/*
61 * Calaculates and sets the affine coordinates of an EC_POINT from the given
62 * compressed coordinates.  Uses algorithm 2.3.4 of SEC 1. Note that the
63 * simple implementation only uses affine coordinates. This algorithm is
64 * patented by Certicom Corp. under US Patent 6,141,420 (for licensing
65 * information, contact licensing@certicom.com). This function is disabled by
66 * default and can be enabled by defining the preprocessor macro
67 * OPENSSL_EC_BIN_PT_COMP at Configure-time.
68 */
69int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group,
70                                              EC_POINT *point,
71                                              const BIGNUM *x_, int y_bit,
72                                              BN_CTX *ctx)
73{
74#ifndef OPENSSL_EC_BIN_PT_COMP
75    ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_DISABLED);
76    return 0;
77#else
78    BN_CTX *new_ctx = NULL;
79    BIGNUM *tmp, *x, *y, *z;
80    int ret = 0, z0;
81
82    /* clear error queue */
83    ERR_clear_error();
84
85    if (ctx == NULL) {
86        ctx = new_ctx = BN_CTX_new();
87        if (ctx == NULL)
88            return 0;
89    }
90
91    y_bit = (y_bit != 0) ? 1 : 0;
92
93    BN_CTX_start(ctx);
94    tmp = BN_CTX_get(ctx);
95    x = BN_CTX_get(ctx);
96    y = BN_CTX_get(ctx);
97    z = BN_CTX_get(ctx);
98    if (z == NULL)
99        goto err;
100
101    if (!BN_GF2m_mod_arr(x, x_, group->poly))
102        goto err;
103    if (BN_is_zero(x)) {
104        if (!BN_GF2m_mod_sqrt_arr(y, &group->b, group->poly, ctx))
105            goto err;
106    } else {
107        if (!group->meth->field_sqr(group, tmp, x, ctx))
108            goto err;
109        if (!group->meth->field_div(group, tmp, &group->b, tmp, ctx))
110            goto err;
111        if (!BN_GF2m_add(tmp, &group->a, tmp))
112            goto err;
113        if (!BN_GF2m_add(tmp, x, tmp))
114            goto err;
115        if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
116            unsigned long err = ERR_peek_last_error();
117
118            if (ERR_GET_LIB(err) == ERR_LIB_BN
119                && ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
120                ERR_clear_error();
121                ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
122                      EC_R_INVALID_COMPRESSED_POINT);
123            } else
124                ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
125                      ERR_R_BN_LIB);
126            goto err;
127        }
128        z0 = (BN_is_odd(z)) ? 1 : 0;
129        if (!group->meth->field_mul(group, y, x, z, ctx))
130            goto err;
131        if (z0 != y_bit) {
132            if (!BN_GF2m_add(y, y, x))
133                goto err;
134        }
135    }
136
137    if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
138        goto err;
139
140    ret = 1;
141
142 err:
143    BN_CTX_end(ctx);
144    if (new_ctx != NULL)
145        BN_CTX_free(new_ctx);
146    return ret;
147#endif
148}
149