1 /* crypto/ec/ec2_oct.c */
2 /* ====================================================================
3 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
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.
9 * The ECC Code is licensed pursuant to the OpenSSL open source
10 * license provided below.
12 * The software is originally written by Sheueling Chang Shantz and
13 * Douglas Stebila of Sun Microsystems Laboratories.
16 /* ====================================================================
17 * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
23 * 1. Redistributions of source code must retain the above copyright
24 * notice, this list of conditions and the following disclaimer.
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
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/)"
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.
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.
45 * 6. Redistributions of any form whatsoever must retain the following
47 * "This product includes software developed by the OpenSSL Project
48 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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 * ====================================================================
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).
70 #include <openssl/err.h>
74 #ifndef OPENSSL_NO_EC2M
77 * Calculates and sets the affine coordinates of an EC_POINT from the given
78 * compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
79 * Note that the simple implementation only uses affine coordinates.
81 * The method is from the following publication:
83 * Harper, Menezes, Vanstone:
84 * "Public-Key Cryptosystems with Very Small Key Lengths",
85 * EUROCRYPT '92, Springer-Verlag LNCS 658,
86 * published February 1993
88 * US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
89 * the same method, but claim no priority date earlier than July 29, 1994
90 * (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
92 int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *point,
93 const BIGNUM *x_, int y_bit, BN_CTX *ctx)
95 BN_CTX *new_ctx = NULL;
96 BIGNUM *tmp, *x, *y, *z;
99 /* clear error queue */
104 ctx = new_ctx = BN_CTX_new();
109 y_bit = (y_bit != 0) ? 1 : 0;
112 tmp = BN_CTX_get(ctx);
116 if (z == NULL) goto err;
118 if (!BN_GF2m_mod_arr(x, x_, group->poly)) goto err;
121 if (!BN_GF2m_mod_sqrt_arr(y, group->b, group->poly, ctx)) goto err;
125 if (!group->meth->field_sqr(group, tmp, x, ctx)) goto err;
126 if (!group->meth->field_div(group, tmp, group->b, tmp, ctx)) goto err;
127 if (!BN_GF2m_add(tmp, group->a, tmp)) goto err;
128 if (!BN_GF2m_add(tmp, x, tmp)) goto err;
129 if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx))
131 unsigned long err = ERR_peek_last_error();
133 if (ERR_GET_LIB(err) == ERR_LIB_BN && ERR_GET_REASON(err) == BN_R_NO_SOLUTION)
136 ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT);
139 ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_BN_LIB);
142 z0 = (BN_is_odd(z)) ? 1 : 0;
143 if (!group->meth->field_mul(group, y, x, z, ctx)) goto err;
146 if (!BN_GF2m_add(y, y, x)) goto err;
150 if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx)) goto err;
157 BN_CTX_free(new_ctx);
162 /* Converts an EC_POINT to an octet string.
163 * If buf is NULL, the encoded length will be returned.
164 * If the length len of buf is smaller than required an error will be returned.
166 size_t ec_GF2m_simple_point2oct(const EC_GROUP *group, const EC_POINT *point, point_conversion_form_t form,
167 unsigned char *buf, size_t len, BN_CTX *ctx)
170 BN_CTX *new_ctx = NULL;
173 size_t field_len, i, skip;
175 if ((form != POINT_CONVERSION_COMPRESSED)
176 && (form != POINT_CONVERSION_UNCOMPRESSED)
177 && (form != POINT_CONVERSION_HYBRID))
179 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
183 if (EC_POINT_is_at_infinity(group, point))
185 /* encodes to a single 0 octet */
190 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
199 /* ret := required output buffer length */
200 field_len = (EC_GROUP_get_degree(group) + 7) / 8;
201 ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len;
203 /* if 'buf' is NULL, just return required length */
208 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
214 ctx = new_ctx = BN_CTX_new();
223 yxi = BN_CTX_get(ctx);
224 if (yxi == NULL) goto err;
226 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx)) goto err;
229 if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x))
231 if (!group->meth->field_div(group, yxi, y, x, ctx)) goto err;
232 if (BN_is_odd(yxi)) buf[0]++;
237 skip = field_len - BN_num_bytes(x);
238 if (skip > field_len)
240 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
248 skip = BN_bn2bin(x, buf + i);
250 if (i != 1 + field_len)
252 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
256 if (form == POINT_CONVERSION_UNCOMPRESSED || form == POINT_CONVERSION_HYBRID)
258 skip = field_len - BN_num_bytes(y);
259 if (skip > field_len)
261 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
269 skip = BN_bn2bin(y, buf + i);
275 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
283 BN_CTX_free(new_ctx);
290 BN_CTX_free(new_ctx);
295 /* Converts an octet string representation to an EC_POINT.
296 * Note that the simple implementation only uses affine coordinates.
298 int ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
299 const unsigned char *buf, size_t len, BN_CTX *ctx)
301 point_conversion_form_t form;
303 BN_CTX *new_ctx = NULL;
305 size_t field_len, enc_len;
310 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
316 if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
317 && (form != POINT_CONVERSION_UNCOMPRESSED)
318 && (form != POINT_CONVERSION_HYBRID))
320 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
323 if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit)
325 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
333 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
337 return EC_POINT_set_to_infinity(group, point);
340 field_len = (EC_GROUP_get_degree(group) + 7) / 8;
341 enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len;
345 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
351 ctx = new_ctx = BN_CTX_new();
359 yxi = BN_CTX_get(ctx);
360 if (yxi == NULL) goto err;
362 if (!BN_bin2bn(buf + 1, field_len, x)) goto err;
363 if (BN_ucmp(x, group->field) >= 0)
365 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
369 if (form == POINT_CONVERSION_COMPRESSED)
371 if (!EC_POINT_set_compressed_coordinates_GF2m(group, point, x, y_bit, ctx)) goto err;
375 if (!BN_bin2bn(buf + 1 + field_len, field_len, y)) goto err;
376 if (BN_ucmp(y, group->field) >= 0)
378 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
381 if (form == POINT_CONVERSION_HYBRID)
383 if (!group->meth->field_div(group, yxi, y, x, ctx)) goto err;
384 if (y_bit != BN_is_odd(yxi))
386 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
391 if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx)) goto err;
394 if (!EC_POINT_is_on_curve(group, point, ctx)) /* test required by X9.62 */
396 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
405 BN_CTX_free(new_ctx);