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1/* crypto/ec/ec2_oct.c */
2/* ====================================================================
3 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
4 *
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.
8 *
9 * The ECC Code is licensed pursuant to the OpenSSL open source
10 * license provided below.
11 *
12 * The software is originally written by Sheueling Chang Shantz and
13 * Douglas Stebila of Sun Microsystems Laboratories.
14 *
15 */
16/* ====================================================================
17 * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
18 *
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
21 * are met:
22 *
23 * 1. Redistributions of source code must retain the above copyright
24 * notice, this list of conditions and the following disclaimer.
25 *
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
29 * distribution.
30 *
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/)"
35 *
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.
40 *
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.
44 *
45 * 6. Redistributions of any form whatsoever must retain the following
46 * acknowledgment:
47 * "This product includes software developed by the OpenSSL Project
48 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
49 *
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 * ====================================================================
63 *
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).
67 *
68 */
69
70#include <openssl/err.h>
71
72#include "ec_lcl.h"
73
74#ifndef OPENSSL_NO_EC2M
75
76/* Calculates and sets the affine coordinates of an EC_POINT from the given
77 * compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
78 * Note that the simple implementation only uses affine coordinates.
79 *
80 * The method is from the following publication:
81 *
82 * Harper, Menezes, Vanstone:
83 * "Public-Key Cryptosystems with Very Small Key Lengths",
84 * EUROCRYPT '92, Springer-Verlag LNCS 658,
85 * published February 1993
86 *
87 * US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
88 * the same method, but claim no priority date earlier than July 29, 1994
89 * (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
90 */
91int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *point,
92 const BIGNUM *x_, int y_bit, BN_CTX *ctx)
93 {
94 BN_CTX *new_ctx = NULL;
95 BIGNUM *tmp, *x, *y, *z;
96 int ret = 0, z0;
97
98 /* clear error queue */
99 ERR_clear_error();
100
101 if (ctx == NULL)
102 {
103 ctx = new_ctx = BN_CTX_new();
104 if (ctx == NULL)
105 return 0;
106 }
107
108 y_bit = (y_bit != 0) ? 1 : 0;
109
110 BN_CTX_start(ctx);
111 tmp = BN_CTX_get(ctx);
112 x = BN_CTX_get(ctx);
113 y = BN_CTX_get(ctx);
114 z = BN_CTX_get(ctx);
115 if (z == NULL) goto err;
116
117 if (!BN_GF2m_mod_arr(x, x_, group->poly)) goto err;
118 if (BN_is_zero(x))
119 {
120 if (!BN_GF2m_mod_sqrt_arr(y, &group->b, group->poly, ctx)) goto err;
121 }
122 else
123 {
124 if (!group->meth->field_sqr(group, tmp, x, ctx)) goto err;
125 if (!group->meth->field_div(group, tmp, &group->b, tmp, ctx)) goto err;
126 if (!BN_GF2m_add(tmp, &group->a, tmp)) goto err;
127 if (!BN_GF2m_add(tmp, x, tmp)) goto err;
128 if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx))
129 {
130 unsigned long err = ERR_peek_last_error();
131
132 if (ERR_GET_LIB(err) == ERR_LIB_BN && ERR_GET_REASON(err) == BN_R_NO_SOLUTION)
133 {
134 ERR_clear_error();
135 ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT);
136 }
137 else
138 ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_BN_LIB);
139 goto err;
140 }
141 z0 = (BN_is_odd(z)) ? 1 : 0;
142 if (!group->meth->field_mul(group, y, x, z, ctx)) goto err;
143 if (z0 != y_bit)
144 {
145 if (!BN_GF2m_add(y, y, x)) goto err;
146 }
147 }
148
149 if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx)) goto err;
150
151 ret = 1;
152
153 err:
154 BN_CTX_end(ctx);
155 if (new_ctx != NULL)
156 BN_CTX_free(new_ctx);
157 return ret;
158 }
159
160
161/* Converts an EC_POINT to an octet string.
162 * If buf is NULL, the encoded length will be returned.
163 * If the length len of buf is smaller than required an error will be returned.
164 */
165size_t ec_GF2m_simple_point2oct(const EC_GROUP *group, const EC_POINT *point, point_conversion_form_t form,
166 unsigned char *buf, size_t len, BN_CTX *ctx)
167 {
168 size_t ret;
169 BN_CTX *new_ctx = NULL;
170 int used_ctx = 0;
171 BIGNUM *x, *y, *yxi;
172 size_t field_len, i, skip;
173
174 if ((form != POINT_CONVERSION_COMPRESSED)
175 && (form != POINT_CONVERSION_UNCOMPRESSED)
176 && (form != POINT_CONVERSION_HYBRID))
177 {
178 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
179 goto err;
180 }
181
182 if (EC_POINT_is_at_infinity(group, point))
183 {
184 /* encodes to a single 0 octet */
185 if (buf != NULL)
186 {
187 if (len < 1)
188 {
189 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
190 return 0;
191 }
192 buf[0] = 0;
193 }
194 return 1;
195 }
196
197
198 /* ret := required output buffer length */
199 field_len = (EC_GROUP_get_degree(group) + 7) / 8;
200 ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len;
201
202 /* if 'buf' is NULL, just return required length */
203 if (buf != NULL)
204 {
205 if (len < ret)
206 {
207 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
208 goto err;
209 }
210
211 if (ctx == NULL)
212 {
213 ctx = new_ctx = BN_CTX_new();
214 if (ctx == NULL)
215 return 0;
216 }
217
218 BN_CTX_start(ctx);
219 used_ctx = 1;
220 x = BN_CTX_get(ctx);
221 y = BN_CTX_get(ctx);
222 yxi = BN_CTX_get(ctx);
223 if (yxi == NULL) goto err;
224
225 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx)) goto err;
226
227 buf[0] = form;
228 if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x))
229 {
230 if (!group->meth->field_div(group, yxi, y, x, ctx)) goto err;
231 if (BN_is_odd(yxi)) buf[0]++;
232 }
233
234 i = 1;
235
236 skip = field_len - BN_num_bytes(x);
237 if (skip > field_len)
238 {
239 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
240 goto err;
241 }
242 while (skip > 0)
243 {
244 buf[i++] = 0;
245 skip--;
246 }
247 skip = BN_bn2bin(x, buf + i);
248 i += skip;
249 if (i != 1 + field_len)
250 {
251 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
252 goto err;
253 }
254
255 if (form == POINT_CONVERSION_UNCOMPRESSED || form == POINT_CONVERSION_HYBRID)
256 {
257 skip = field_len - BN_num_bytes(y);
258 if (skip > field_len)
259 {
260 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
261 goto err;
262 }
263 while (skip > 0)
264 {
265 buf[i++] = 0;
266 skip--;
267 }
268 skip = BN_bn2bin(y, buf + i);
269 i += skip;
270 }
271
272 if (i != ret)
273 {
274 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
275 goto err;
276 }
277 }
278
279 if (used_ctx)
280 BN_CTX_end(ctx);
281 if (new_ctx != NULL)
282 BN_CTX_free(new_ctx);
283 return ret;
284
285 err:
286 if (used_ctx)
287 BN_CTX_end(ctx);
288 if (new_ctx != NULL)
289 BN_CTX_free(new_ctx);
290 return 0;
291 }
292
293
294/* Converts an octet string representation to an EC_POINT.
295 * Note that the simple implementation only uses affine coordinates.
296 */
297int ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
298 const unsigned char *buf, size_t len, BN_CTX *ctx)
299 {
300 point_conversion_form_t form;
301 int y_bit;
302 BN_CTX *new_ctx = NULL;
303 BIGNUM *x, *y, *yxi;
304 size_t field_len, enc_len;
305 int ret = 0;
306
307 if (len == 0)
308 {
309 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
310 return 0;
311 }
312 form = buf[0];
313 y_bit = form & 1;
314 form = form & ~1U;
315 if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
316 && (form != POINT_CONVERSION_UNCOMPRESSED)
317 && (form != POINT_CONVERSION_HYBRID))
318 {
319 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
320 return 0;
321 }
322 if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit)
323 {
324 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
325 return 0;
326 }
327
328 if (form == 0)
329 {
330 if (len != 1)
331 {
332 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
333 return 0;
334 }
335
336 return EC_POINT_set_to_infinity(group, point);
337 }
338
339 field_len = (EC_GROUP_get_degree(group) + 7) / 8;
340 enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len;
341
342 if (len != enc_len)
343 {
344 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
345 return 0;
346 }
347
348 if (ctx == NULL)
349 {
350 ctx = new_ctx = BN_CTX_new();
351 if (ctx == NULL)
352 return 0;
353 }
354
355 BN_CTX_start(ctx);
356 x = BN_CTX_get(ctx);
357 y = BN_CTX_get(ctx);
358 yxi = BN_CTX_get(ctx);
359 if (yxi == NULL) goto err;
360
361 if (!BN_bin2bn(buf + 1, field_len, x)) goto err;
362 if (BN_ucmp(x, &group->field) >= 0)
363 {
364 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
365 goto err;
366 }
367
368 if (form == POINT_CONVERSION_COMPRESSED)
369 {
370 if (!EC_POINT_set_compressed_coordinates_GF2m(group, point, x, y_bit, ctx)) goto err;
371 }
372 else
373 {
374 if (!BN_bin2bn(buf + 1 + field_len, field_len, y)) goto err;
375 if (BN_ucmp(y, &group->field) >= 0)
376 {
377 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
378 goto err;
379 }
380 if (form == POINT_CONVERSION_HYBRID)
381 {
382 if (!group->meth->field_div(group, yxi, y, x, ctx)) goto err;
383 if (y_bit != BN_is_odd(yxi))
384 {
385 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
386 goto err;
387 }
388 }
389
390 if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx)) goto err;
391 }
392
393 if (!EC_POINT_is_on_curve(group, point, ctx)) /* test required by X9.62 */
394 {
395 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
396 goto err;
397 }
398
399 ret = 1;
400
401 err:
402 BN_CTX_end(ctx);
403 if (new_ctx != NULL)
404 BN_CTX_free(new_ctx);
405 return ret;
406 }
407#endif
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