1EC_GROUP_COPY(3ossl) OpenSSL EC_GROUP_COPY(3ossl)
2
6 EC_GROUP_get0_order, EC_GROUP_order_bits, EC_GROUP_get0_cofactor,
7 EC_GROUP_copy, EC_GROUP_dup, EC_GROUP_method_of,
8 EC_GROUP_set_generator, EC_GROUP_get0_generator, EC_GROUP_get_order,
9 EC_GROUP_get_cofactor, EC_GROUP_set_curve_name,
10 EC_GROUP_get_curve_name, EC_GROUP_set_asn1_flag,
11 EC_GROUP_get_asn1_flag, EC_GROUP_set_point_conversion_form,
12 EC_GROUP_get_point_conversion_form, EC_GROUP_get0_seed,
13 EC_GROUP_get_seed_len, EC_GROUP_set_seed, EC_GROUP_get_degree,
14 EC_GROUP_check, EC_GROUP_check_named_curve,
15 EC_GROUP_check_discriminant, EC_GROUP_cmp, EC_GROUP_get_basis_type,
16 EC_GROUP_get_trinomial_basis, EC_GROUP_get_pentanomial_basis,
17 EC_GROUP_get0_field, EC_GROUP_get_field_type - Functions for
18 manipulating EC_GROUP objects
19
21 #include <openssl/ec.h>
22 int EC_GROUP_copy(EC_GROUP *dst, const EC_GROUP *src);
24 EC_GROUP *EC_GROUP_dup(const EC_GROUP *src);
25 int EC_GROUP_set_generator(EC_GROUP *group, const EC_POINT *generator,
27 const BIGNUM *order, const BIGNUM *cofactor);
28 const EC_POINT *EC_GROUP_get0_generator(const EC_GROUP *group);
29 int EC_GROUP_get_order(const EC_GROUP *group, BIGNUM *order, BN_CTX *ctx);
31 const BIGNUM *EC_GROUP_get0_order(const EC_GROUP *group);
32 int EC_GROUP_order_bits(const EC_GROUP *group);
33 int EC_GROUP_get_cofactor(const EC_GROUP *group, BIGNUM *cofactor, BN_CTX *ctx);
34 const BIGNUM *EC_GROUP_get0_cofactor(const EC_GROUP *group);
35 const BIGNUM *EC_GROUP_get0_field(const EC_GROUP *group);
36 void EC_GROUP_set_curve_name(EC_GROUP *group, int nid);
38 int EC_GROUP_get_curve_name(const EC_GROUP *group);
39 void EC_GROUP_set_asn1_flag(EC_GROUP *group, int flag);
41 int EC_GROUP_get_asn1_flag(const EC_GROUP *group);
42 void EC_GROUP_set_point_conversion_form(EC_GROUP *group, point_conversion_form_t form);
44 point_conversion_form_t EC_GROUP_get_point_conversion_form(const EC_GROUP *group);
45 unsigned char *EC_GROUP_get0_seed(const EC_GROUP *group);
47 size_t EC_GROUP_get_seed_len(const EC_GROUP *group);
48 size_t EC_GROUP_set_seed(EC_GROUP *group, const unsigned char *, size_t len);
49 int EC_GROUP_get_degree(const EC_GROUP *group);
51 int EC_GROUP_check(const EC_GROUP *group, BN_CTX *ctx);
53 int EC_GROUP_check_named_curve(const EC_GROUP *group, int nist_only,
54 BN_CTX *ctx);
55 int EC_GROUP_check_discriminant(const EC_GROUP *group, BN_CTX *ctx);
57 int EC_GROUP_cmp(const EC_GROUP *a, const EC_GROUP *b, BN_CTX *ctx);
59 int EC_GROUP_get_basis_type(const EC_GROUP *group);
61 int EC_GROUP_get_trinomial_basis(const EC_GROUP *group, unsigned int *k);
62 int EC_GROUP_get_pentanomial_basis(const EC_GROUP *group, unsigned int *k1,
63 unsigned int *k2, unsigned int *k3);
64 int EC_GROUP_get_field_type(const EC_GROUP *group);
66 The following function has been deprecated since OpenSSL 3.0, and can
68 be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
69 version value, see openssl_user_macros(7):
70 const EC_METHOD *EC_GROUP_method_of(const EC_GROUP *group);
72
74 EC_GROUP_copy() copies the curve src into dst. Both src and dst must
75 use the same EC_METHOD.
76 EC_GROUP_dup() creates a new EC_GROUP object and copies the content
78 from src to the newly created EC_GROUP object.
79 EC_GROUP_method_of() obtains the EC_METHOD of group. This function was
81 deprecated in OpenSSL 3.0, since EC_METHOD is no longer a public
82 concept.
83 EC_GROUP_set_generator() sets curve parameters that must be agreed by
85 all participants using the curve. These parameters include the
86 generator, the order and the cofactor. The generator is a well defined
87 point on the curve chosen for cryptographic operations. Integers used
88 for point multiplications will be between 0 and n-1 where n is the
89 order. The order multiplied by the cofactor gives the number of points
90 on the curve.
91 EC_GROUP_get0_generator() returns the generator for the identified
93 group.
94 EC_GROUP_get_order() retrieves the order of group and copies its value
96 into order. It fails in case group is not fully initialized (i.e., its
97 order is not set or set to zero).
98 EC_GROUP_get_cofactor() retrieves the cofactor of group and copies its
100 value into cofactor. It fails in case group is not fully initialized
101 or if the cofactor is not set (or set to zero).
102 The functions EC_GROUP_set_curve_name() and EC_GROUP_get_curve_name(),
104 set and get the NID for the curve respectively (see EC_GROUP_new(3)).
105 If a curve does not have a NID associated with it, then
106 EC_GROUP_get_curve_name will return NID_undef.
107 The asn1_flag value is used to determine whether the curve encoding
109 uses explicit parameters or a named curve using an ASN1 OID: many
110 applications only support the latter form. If asn1_flag is
111 OPENSSL_EC_NAMED_CURVE then the named curve form is used and the
112 parameters must have a corresponding named curve NID set. If asn1_flags
113 is OPENSSL_EC_EXPLICIT_CURVE the parameters are explicitly encoded. The
114 functions EC_GROUP_get_asn1_flag() and EC_GROUP_set_asn1_flag() get and
115 set the status of the asn1_flag for the curve. Note:
116 OPENSSL_EC_EXPLICIT_CURVE was added in OpenSSL 1.1.0, for previous
117 versions of OpenSSL the value 0 must be used instead. Before OpenSSL
118 1.1.0 the default form was to use explicit parameters (meaning that
119 applications would have to explicitly set the named curve form) in
120 OpenSSL 1.1.0 and later the named curve form is the default.
121 The point_conversion_form for a curve controls how EC_POINT data is
123 encoded as ASN1 as defined in X9.62 (ECDSA). point_conversion_form_t
124 is an enum defined as follows:
125 typedef enum {
127 /** the point is encoded as z||x, where the octet z specifies
128 * which solution of the quadratic equation y is */
129 POINT_CONVERSION_COMPRESSED = 2,
130 /** the point is encoded as z||x||y, where z is the octet 0x04 */
131 POINT_CONVERSION_UNCOMPRESSED = 4,
132 /** the point is encoded as z||x||y, where the octet z specifies
133 * which solution of the quadratic equation y is */
134 POINT_CONVERSION_HYBRID = 6
135 } point_conversion_form_t;
136 For POINT_CONVERSION_UNCOMPRESSED the point is encoded as an octet
138 signifying the UNCOMPRESSED form has been used followed by the octets
139 for x, followed by the octets for y.
140 For any given x co-ordinate for a point on a curve it is possible to
142 derive two possible y values. For POINT_CONVERSION_COMPRESSED the point
143 is encoded as an octet signifying that the COMPRESSED form has been
144 used AND which of the two possible solutions for y has been used,
145 followed by the octets for x.
146 For POINT_CONVERSION_HYBRID the point is encoded as an octet signifying
148 the HYBRID form has been used AND which of the two possible solutions
149 for y has been used, followed by the octets for x, followed by the
150 octets for y.
151 The functions EC_GROUP_set_point_conversion_form() and
153 EC_GROUP_get_point_conversion_form(), set and get the
154 point_conversion_form for the curve respectively.
155 ANSI X9.62 (ECDSA standard) defines a method of generating the curve
157 parameter b from a random number. This provides advantages in that a
158 parameter obtained in this way is highly unlikely to be susceptible to
159 special purpose attacks, or have any trapdoors in it. If the seed is
160 present for a curve then the b parameter was generated in a verifiable
161 fashion using that seed. The OpenSSL EC library does not use this seed
162 value but does enable you to inspect it using EC_GROUP_get0_seed().
163 This returns a pointer to a memory block containing the seed that was
164 used. The length of the memory block can be obtained using
165 EC_GROUP_get_seed_len(). A number of the built-in curves within the
166 library provide seed values that can be obtained. It is also possible
167 to set a custom seed using EC_GROUP_set_seed() and passing a pointer to
168 a memory block, along with the length of the seed. Again, the EC
169 library will not use this seed value, although it will be preserved in
170 any ASN1 based communications.
171 EC_GROUP_get_degree() gets the degree of the field. For Fp fields this
173 will be the number of bits in p. For F2^m fields this will be the
174 value m.
175 EC_GROUP_get_field_type() identifies what type of field the EC_GROUP
177 structure supports, which will be either F2^m or Fp.
178 The function EC_GROUP_check_discriminant() calculates the discriminant
180 for the curve and verifies that it is valid. For a curve defined over
181 Fp the discriminant is given by the formula 4*a^3 + 27*b^2 whilst for
182 F2^m curves the discriminant is simply b. In either case for the curve
183 to be valid the discriminant must be non zero.
184 The function EC_GROUP_check() behaves in the following way: For the
186 OpenSSL default provider it performs a number of checks on a curve to
187 verify that it is valid. Checks performed include verifying that the
188 discriminant is non zero; that a generator has been defined; that the
189 generator is on the curve and has the correct order. For the OpenSSL
190 FIPS provider it uses EC_GROUP_check_named_curve() to conform to
191 SP800-56Ar3.
192 The function EC_GROUP_check_named_curve() determines if the group's
194 domain parameters match one of the built-in curves supported by the
195 library. The curve name is returned as a NID if it matches. If the
196 group's domain parameters have been modified then no match will be
197 found. If the curve name of the given group is NID_undef (e.g. it has
198 been created by using explicit parameters with no curve name), then
199 this method can be used to lookup the name of the curve that matches
200 the group domain parameters. The built-in curves contain aliases, so
201 that multiple NID's can map to the same domain parameters. For such
202 curves it is unspecified which of the aliases will be returned if the
203 curve name of the given group is NID_undef. If nist_only is 1 it will
204 only look for NIST approved curves, otherwise it searches all built-in
205 curves. This function may be passed a BN_CTX object in the ctx
206 parameter. The ctx parameter may be NULL.
207 EC_GROUP_cmp() compares a and b to determine whether they represent the
209 same curve or not.
210 The functions EC_GROUP_get_basis_type(), EC_GROUP_get_trinomial_basis()
212 and EC_GROUP_get_pentanomial_basis() should only be called for curves
213 defined over an F2^m field. Addition and multiplication operations
214 within an F2^m field are performed using an irreducible polynomial
215 function f(x). This function is either a trinomial of the form:
216 f(x) = x^m + x^k + 1 with m > k >= 1
218 or a pentanomial of the form:
220 f(x) = x^m + x^k3 + x^k2 + x^k1 + 1 with m > k3 > k2 > k1 >= 1
222 The function EC_GROUP_get_basis_type() returns a NID identifying
224 whether a trinomial or pentanomial is in use for the field. The
225 function EC_GROUP_get_trinomial_basis() must only be called where f(x)
226 is of the trinomial form, and returns the value of k. Similarly the
227 function EC_GROUP_get_pentanomial_basis() must only be called where
228 f(x) is of the pentanomial form, and returns the values of k1, k2 and
229 k3 respectively.
230
232 The following functions return 1 on success or 0 on error:
233 EC_GROUP_copy(), EC_GROUP_set_generator(), EC_GROUP_check(),
234 EC_GROUP_check_discriminant(), EC_GROUP_get_trinomial_basis() and
235 EC_GROUP_get_pentanomial_basis().
236 EC_GROUP_dup() returns a pointer to the duplicated curve, or NULL on
238 error.
239 EC_GROUP_method_of() returns the EC_METHOD implementation in use for
241 the given curve or NULL on error.
242 EC_GROUP_get0_generator() returns the generator for the given curve or
244 NULL on error.
245 EC_GROUP_get_order() returns 0 if the order is not set (or set to zero)
247 for group or if copying into order fails, 1 otherwise.
248 EC_GROUP_get_cofactor() returns 0 if the cofactor is not set (or is set
250 to zero) for group or if copying into cofactor fails, 1 otherwise.
251 EC_GROUP_get_curve_name() returns the curve name (NID) for group or
253 will return NID_undef if no curve name is associated.
254 EC_GROUP_get_asn1_flag() returns the ASN1 flag for the specified group
256 .
257 EC_GROUP_get_point_conversion_form() returns the point_conversion_form
259 for group.
260 EC_GROUP_get_degree() returns the degree for group or 0 if the
262 operation is not supported by the underlying group implementation.
263 EC_GROUP_get_field_type() returns either NID_X9_62_prime_field for
265 prime curves or NID_X9_62_characteristic_two_field for binary curves;
266 these values are defined in the <openssl/obj_mac.h> header file.
267 EC_GROUP_check_named_curve() returns the nid of the matching named
269 curve, otherwise it returns 0 for no match, or -1 on error.
270 EC_GROUP_get0_order() returns an internal pointer to the group order.
272 EC_GROUP_order_bits() returns the number of bits in the group order.
273 EC_GROUP_get0_cofactor() returns an internal pointer to the group
274 cofactor. EC_GROUP_get0_field() returns an internal pointer to the
275 group field. For curves over GF(p), this is the modulus; for curves
276 over GF(2^m), this is the irreducible polynomial defining the field.
277 EC_GROUP_get0_seed() returns a pointer to the seed that was used to
279 generate the parameter b, or NULL if the seed is not specified.
280 EC_GROUP_get_seed_len() returns the length of the seed or 0 if the seed
281 is not specified.
282 EC_GROUP_set_seed() returns the length of the seed that has been set.
284 If the supplied seed is NULL, or the supplied seed length is 0, the
285 return value will be 1. On error 0 is returned.
286 EC_GROUP_cmp() returns 0 if the curves are equal, 1 if they are not
288 equal, or -1 on error.
289 EC_GROUP_get_basis_type() returns the values NID_X9_62_tpBasis or
291 NID_X9_62_ppBasis (as defined in <openssl/obj_mac.h>) for a trinomial
292 or pentanomial respectively. Alternatively in the event of an error a 0
293 is returned.
294
296 crypto(7), EC_GROUP_new(3), EC_POINT_new(3), EC_POINT_add(3),
297 EC_KEY_new(3), EC_GFp_simple_method(3), d2i_ECPKParameters(3)
298
300 EC_GROUP_method_of() was deprecated in OpenSSL 3.0.
301 EC_GROUP_check_named_curve() and EC_GROUP_get_field_type() were added
303 in OpenSSL 3.0.
304
306 Copyright 2013-2022 The OpenSSL Project Authors. All Rights Reserved.
307 Licensed under the Apache License 2.0 (the "License"). You may not use
309 this file except in compliance with the License. You can obtain a copy
310 in the file LICENSE in the source distribution or at
311 <https://www.openssl.org/source/license.html>.
3123.0.5 2022-11-01 EC_GROUP_COPY(3ossl)