ecp_oct.c revision 1.2
1/* crypto/ec/ecp_oct.c */ 2/* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de> 3 * for the OpenSSL project. 4 * Includes code written by Bodo Moeller 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 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED. 61 * Portions of this software developed by SUN MICROSYSTEMS, INC., 62 * and contributed to the OpenSSL project. 63 */ 64 65#include <openssl/err.h> 66 67#include "ec_lcl.h" 68 69int ec_GFp_simple_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *point, 70 const BIGNUM *x_, int y_bit, BN_CTX *ctx) 71 { 72 BN_CTX *new_ctx = NULL; 73 BIGNUM *tmp1, *tmp2, *x, *y; 74 int ret = 0; 75 76 /* clear error queue*/ 77 ERR_clear_error(); 78 79 if (ctx == NULL) 80 { 81 ctx = new_ctx = BN_CTX_new(); 82 if (ctx == NULL) 83 return 0; 84 } 85 86 y_bit = (y_bit != 0); 87 88 BN_CTX_start(ctx); 89 tmp1 = BN_CTX_get(ctx); 90 tmp2 = BN_CTX_get(ctx); 91 x = BN_CTX_get(ctx); 92 y = BN_CTX_get(ctx); 93 if (y == NULL) goto err; 94 95 /* Recover y. We have a Weierstrass equation 96 * y^2 = x^3 + a*x + b, 97 * so y is one of the square roots of x^3 + a*x + b. 98 */ 99 100 /* tmp1 := x^3 */ 101 if (!BN_nnmod(x, x_, &group->field,ctx)) goto err; 102 if (group->meth->field_decode == 0) 103 { 104 /* field_{sqr,mul} work on standard representation */ 105 if (!group->meth->field_sqr(group, tmp2, x_, ctx)) goto err; 106 if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx)) goto err; 107 } 108 else 109 { 110 if (!BN_mod_sqr(tmp2, x_, &group->field, ctx)) goto err; 111 if (!BN_mod_mul(tmp1, tmp2, x_, &group->field, ctx)) goto err; 112 } 113 114 /* tmp1 := tmp1 + a*x */ 115 if (group->a_is_minus3) 116 { 117 if (!BN_mod_lshift1_quick(tmp2, x, &group->field)) goto err; 118 if (!BN_mod_add_quick(tmp2, tmp2, x, &group->field)) goto err; 119 if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, &group->field)) goto err; 120 } 121 else 122 { 123 if (group->meth->field_decode) 124 { 125 if (!group->meth->field_decode(group, tmp2, &group->a, ctx)) goto err; 126 if (!BN_mod_mul(tmp2, tmp2, x, &group->field, ctx)) goto err; 127 } 128 else 129 { 130 /* field_mul works on standard representation */ 131 if (!group->meth->field_mul(group, tmp2, &group->a, x, ctx)) goto err; 132 } 133 134 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) goto err; 135 } 136 137 /* tmp1 := tmp1 + b */ 138 if (group->meth->field_decode) 139 { 140 if (!group->meth->field_decode(group, tmp2, &group->b, ctx)) goto err; 141 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) goto err; 142 } 143 else 144 { 145 if (!BN_mod_add_quick(tmp1, tmp1, &group->b, &group->field)) goto err; 146 } 147 148 if (!BN_mod_sqrt(y, tmp1, &group->field, ctx)) 149 { 150 unsigned long err = ERR_peek_last_error(); 151 152 if (ERR_GET_LIB(err) == ERR_LIB_BN && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) 153 { 154 ERR_clear_error(); 155 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT); 156 } 157 else 158 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_BN_LIB); 159 goto err; 160 } 161 162 if (y_bit != BN_is_odd(y)) 163 { 164 if (BN_is_zero(y)) 165 { 166 int kron; 167 168 kron = BN_kronecker(x, &group->field, ctx); 169 if (kron == -2) goto err; 170 171 if (kron == 1) 172 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSION_BIT); 173 else 174 /* BN_mod_sqrt() should have cought this error (not a square) */ 175 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT); 176 goto err; 177 } 178 if (!BN_usub(y, &group->field, y)) goto err; 179 } 180 if (y_bit != BN_is_odd(y)) 181 { 182 ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_INTERNAL_ERROR); 183 goto err; 184 } 185 186 if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) goto err; 187 188 ret = 1; 189 190 err: 191 BN_CTX_end(ctx); 192 if (new_ctx != NULL) 193 BN_CTX_free(new_ctx); 194 return ret; 195 } 196 197 198size_t ec_GFp_simple_point2oct(const EC_GROUP *group, const EC_POINT *point, point_conversion_form_t form, 199 unsigned char *buf, size_t len, BN_CTX *ctx) 200 { 201 size_t ret; 202 BN_CTX *new_ctx = NULL; 203 int used_ctx = 0; 204 BIGNUM *x, *y; 205 size_t field_len, i, skip; 206 207 if ((form != POINT_CONVERSION_COMPRESSED) 208 && (form != POINT_CONVERSION_UNCOMPRESSED) 209 && (form != POINT_CONVERSION_HYBRID)) 210 { 211 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_INVALID_FORM); 212 goto err; 213 } 214 215 if (EC_POINT_is_at_infinity(group, point)) 216 { 217 /* encodes to a single 0 octet */ 218 if (buf != NULL) 219 { 220 if (len < 1) 221 { 222 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL); 223 return 0; 224 } 225 buf[0] = 0; 226 } 227 return 1; 228 } 229 230 231 /* ret := required output buffer length */ 232 field_len = BN_num_bytes(&group->field); 233 ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len; 234 235 /* if 'buf' is NULL, just return required length */ 236 if (buf != NULL) 237 { 238 if (len < ret) 239 { 240 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL); 241 goto err; 242 } 243 244 if (ctx == NULL) 245 { 246 ctx = new_ctx = BN_CTX_new(); 247 if (ctx == NULL) 248 return 0; 249 } 250 251 BN_CTX_start(ctx); 252 used_ctx = 1; 253 x = BN_CTX_get(ctx); 254 y = BN_CTX_get(ctx); 255 if (y == NULL) goto err; 256 257 if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx)) goto err; 258 259 if ((form == POINT_CONVERSION_COMPRESSED || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y)) 260 buf[0] = form + 1; 261 else 262 buf[0] = form; 263 264 i = 1; 265 266 skip = field_len - BN_num_bytes(x); 267 if (skip > field_len) 268 { 269 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 270 goto err; 271 } 272 while (skip > 0) 273 { 274 buf[i++] = 0; 275 skip--; 276 } 277 skip = BN_bn2bin(x, buf + i); 278 i += skip; 279 if (i != 1 + field_len) 280 { 281 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 282 goto err; 283 } 284 285 if (form == POINT_CONVERSION_UNCOMPRESSED || form == POINT_CONVERSION_HYBRID) 286 { 287 skip = field_len - BN_num_bytes(y); 288 if (skip > field_len) 289 { 290 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 291 goto err; 292 } 293 while (skip > 0) 294 { 295 buf[i++] = 0; 296 skip--; 297 } 298 skip = BN_bn2bin(y, buf + i); 299 i += skip; 300 } 301 302 if (i != ret) 303 { 304 ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR); 305 goto err; 306 } 307 } 308 309 if (used_ctx) 310 BN_CTX_end(ctx); 311 if (new_ctx != NULL) 312 BN_CTX_free(new_ctx); 313 return ret; 314 315 err: 316 if (used_ctx) 317 BN_CTX_end(ctx); 318 if (new_ctx != NULL) 319 BN_CTX_free(new_ctx); 320 return 0; 321 } 322 323 324int ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point, 325 const unsigned char *buf, size_t len, BN_CTX *ctx) 326 { 327 point_conversion_form_t form; 328 int y_bit; 329 BN_CTX *new_ctx = NULL; 330 BIGNUM *x, *y; 331 size_t field_len, enc_len; 332 int ret = 0; 333 334 if (len == 0) 335 { 336 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL); 337 return 0; 338 } 339 form = buf[0]; 340 y_bit = form & 1; 341 form = form & ~1U; 342 if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED) 343 && (form != POINT_CONVERSION_UNCOMPRESSED) 344 && (form != POINT_CONVERSION_HYBRID)) 345 { 346 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 347 return 0; 348 } 349 if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) 350 { 351 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 352 return 0; 353 } 354 355 if (form == 0) 356 { 357 if (len != 1) 358 { 359 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 360 return 0; 361 } 362 363 return EC_POINT_set_to_infinity(group, point); 364 } 365 366 field_len = BN_num_bytes(&group->field); 367 enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len; 368 369 if (len != enc_len) 370 { 371 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 372 return 0; 373 } 374 375 if (ctx == NULL) 376 { 377 ctx = new_ctx = BN_CTX_new(); 378 if (ctx == NULL) 379 return 0; 380 } 381 382 BN_CTX_start(ctx); 383 x = BN_CTX_get(ctx); 384 y = BN_CTX_get(ctx); 385 if (y == NULL) goto err; 386 387 if (!BN_bin2bn(buf + 1, field_len, x)) goto err; 388 if (BN_ucmp(x, &group->field) >= 0) 389 { 390 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 391 goto err; 392 } 393 394 if (form == POINT_CONVERSION_COMPRESSED) 395 { 396 if (!EC_POINT_set_compressed_coordinates_GFp(group, point, x, y_bit, ctx)) goto err; 397 } 398 else 399 { 400 if (!BN_bin2bn(buf + 1 + field_len, field_len, y)) goto err; 401 if (BN_ucmp(y, &group->field) >= 0) 402 { 403 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 404 goto err; 405 } 406 if (form == POINT_CONVERSION_HYBRID) 407 { 408 if (y_bit != BN_is_odd(y)) 409 { 410 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING); 411 goto err; 412 } 413 } 414 415 if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) goto err; 416 } 417 418 if (!EC_POINT_is_on_curve(group, point, ctx)) /* test required by X9.62 */ 419 { 420 ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE); 421 goto err; 422 } 423 424 ret = 1; 425 426 err: 427 BN_CTX_end(ctx); 428 if (new_ctx != NULL) 429 BN_CTX_free(new_ctx); 430 return ret; 431 } 432 433