2 * Copyright 2011-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
10 /* ====================================================================
11 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
13 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
14 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
15 * to the OpenSSL project.
17 * The ECC Code is licensed pursuant to the OpenSSL open source
18 * license provided below.
20 * The software is originally written by Sheueling Chang Shantz and
21 * Douglas Stebila of Sun Microsystems Laboratories.
25 #include <openssl/err.h>
29 #ifndef OPENSSL_NO_EC2M
32 * Calculates and sets the affine coordinates of an EC_POINT from the given
33 * compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
34 * Note that the simple implementation only uses affine coordinates.
36 * The method is from the following publication:
38 * Harper, Menezes, Vanstone:
39 * "Public-Key Cryptosystems with Very Small Key Lengths",
40 * EUROCRYPT '92, Springer-Verlag LNCS 658,
41 * published February 1993
43 * US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
44 * the same method, but claim no priority date earlier than July 29, 1994
45 * (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
47 int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP
*group
,
49 const BIGNUM
*x_
, int y_bit
,
52 BN_CTX
*new_ctx
= NULL
;
53 BIGNUM
*tmp
, *x
, *y
, *z
;
56 /* clear error queue */
60 ctx
= new_ctx
= BN_CTX_new();
65 y_bit
= (y_bit
!= 0) ? 1 : 0;
68 tmp
= BN_CTX_get(ctx
);
75 if (!BN_GF2m_mod_arr(x
, x_
, group
->poly
))
78 if (!BN_GF2m_mod_sqrt_arr(y
, group
->b
, group
->poly
, ctx
))
81 if (!group
->meth
->field_sqr(group
, tmp
, x
, ctx
))
83 if (!group
->meth
->field_div(group
, tmp
, group
->b
, tmp
, ctx
))
85 if (!BN_GF2m_add(tmp
, group
->a
, tmp
))
87 if (!BN_GF2m_add(tmp
, x
, tmp
))
89 if (!BN_GF2m_mod_solve_quad_arr(z
, tmp
, group
->poly
, ctx
)) {
90 unsigned long err
= ERR_peek_last_error();
92 if (ERR_GET_LIB(err
) == ERR_LIB_BN
93 && ERR_GET_REASON(err
) == BN_R_NO_SOLUTION
) {
95 ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES
,
96 EC_R_INVALID_COMPRESSED_POINT
);
98 ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES
,
102 z0
= (BN_is_odd(z
)) ? 1 : 0;
103 if (!group
->meth
->field_mul(group
, y
, x
, z
, ctx
))
106 if (!BN_GF2m_add(y
, y
, x
))
111 if (!EC_POINT_set_affine_coordinates_GF2m(group
, point
, x
, y
, ctx
))
118 BN_CTX_free(new_ctx
);
123 * Converts an EC_POINT to an octet string. If buf is NULL, the encoded
124 * length will be returned. If the length len of buf is smaller than required
125 * an error will be returned.
127 size_t ec_GF2m_simple_point2oct(const EC_GROUP
*group
, const EC_POINT
*point
,
128 point_conversion_form_t form
,
129 unsigned char *buf
, size_t len
, BN_CTX
*ctx
)
132 BN_CTX
*new_ctx
= NULL
;
135 size_t field_len
, i
, skip
;
137 if ((form
!= POINT_CONVERSION_COMPRESSED
)
138 && (form
!= POINT_CONVERSION_UNCOMPRESSED
)
139 && (form
!= POINT_CONVERSION_HYBRID
)) {
140 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT
, EC_R_INVALID_FORM
);
144 if (EC_POINT_is_at_infinity(group
, point
)) {
145 /* encodes to a single 0 octet */
148 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT
, EC_R_BUFFER_TOO_SMALL
);
156 /* ret := required output buffer length */
157 field_len
= (EC_GROUP_get_degree(group
) + 7) / 8;
160 POINT_CONVERSION_COMPRESSED
) ? 1 + field_len
: 1 + 2 * field_len
;
162 /* if 'buf' is NULL, just return required length */
165 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT
, EC_R_BUFFER_TOO_SMALL
);
170 ctx
= new_ctx
= BN_CTX_new();
179 yxi
= BN_CTX_get(ctx
);
183 if (!EC_POINT_get_affine_coordinates_GF2m(group
, point
, x
, y
, ctx
))
187 if ((form
!= POINT_CONVERSION_UNCOMPRESSED
) && !BN_is_zero(x
)) {
188 if (!group
->meth
->field_div(group
, yxi
, y
, x
, ctx
))
196 skip
= field_len
- BN_num_bytes(x
);
197 if (skip
> field_len
) {
198 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT
, ERR_R_INTERNAL_ERROR
);
205 skip
= BN_bn2bin(x
, buf
+ i
);
207 if (i
!= 1 + field_len
) {
208 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT
, ERR_R_INTERNAL_ERROR
);
212 if (form
== POINT_CONVERSION_UNCOMPRESSED
213 || form
== POINT_CONVERSION_HYBRID
) {
214 skip
= field_len
- BN_num_bytes(y
);
215 if (skip
> field_len
) {
216 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT
, ERR_R_INTERNAL_ERROR
);
223 skip
= BN_bn2bin(y
, buf
+ i
);
228 ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT
, ERR_R_INTERNAL_ERROR
);
235 BN_CTX_free(new_ctx
);
241 BN_CTX_free(new_ctx
);
246 * Converts an octet string representation to an EC_POINT. Note that the
247 * simple implementation only uses affine coordinates.
249 int ec_GF2m_simple_oct2point(const EC_GROUP
*group
, EC_POINT
*point
,
250 const unsigned char *buf
, size_t len
,
253 point_conversion_form_t form
;
255 BN_CTX
*new_ctx
= NULL
;
257 size_t field_len
, enc_len
;
261 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_BUFFER_TOO_SMALL
);
267 if ((form
!= 0) && (form
!= POINT_CONVERSION_COMPRESSED
)
268 && (form
!= POINT_CONVERSION_UNCOMPRESSED
)
269 && (form
!= POINT_CONVERSION_HYBRID
)) {
270 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_INVALID_ENCODING
);
273 if ((form
== 0 || form
== POINT_CONVERSION_UNCOMPRESSED
) && y_bit
) {
274 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_INVALID_ENCODING
);
280 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_INVALID_ENCODING
);
284 return EC_POINT_set_to_infinity(group
, point
);
287 field_len
= (EC_GROUP_get_degree(group
) + 7) / 8;
290 POINT_CONVERSION_COMPRESSED
) ? 1 + field_len
: 1 + 2 * field_len
;
292 if (len
!= enc_len
) {
293 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_INVALID_ENCODING
);
298 ctx
= new_ctx
= BN_CTX_new();
306 yxi
= BN_CTX_get(ctx
);
310 if (!BN_bin2bn(buf
+ 1, field_len
, x
))
312 if (BN_ucmp(x
, group
->field
) >= 0) {
313 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_INVALID_ENCODING
);
317 if (form
== POINT_CONVERSION_COMPRESSED
) {
318 if (!EC_POINT_set_compressed_coordinates_GF2m
319 (group
, point
, x
, y_bit
, ctx
))
322 if (!BN_bin2bn(buf
+ 1 + field_len
, field_len
, y
))
324 if (BN_ucmp(y
, group
->field
) >= 0) {
325 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_INVALID_ENCODING
);
328 if (form
== POINT_CONVERSION_HYBRID
) {
329 if (!group
->meth
->field_div(group
, yxi
, y
, x
, ctx
))
331 if (y_bit
!= BN_is_odd(yxi
)) {
332 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_INVALID_ENCODING
);
337 if (!EC_POINT_set_affine_coordinates_GF2m(group
, point
, x
, y
, ctx
))
341 /* test required by X9.62 */
342 if (EC_POINT_is_on_curve(group
, point
, ctx
) <= 0) {
343 ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT
, EC_R_POINT_IS_NOT_ON_CURVE
);
351 BN_CTX_free(new_ctx
);