xref: /openssl/doc/man3/EC_KEY_new.pod (revision da1c088f) 
1=pod
2
3=head1 NAME
4
5EVP_EC_gen,
6EC_KEY_get_method, EC_KEY_set_method, EC_KEY_new_ex,
7EC_KEY_new, EC_KEY_get_flags, EC_KEY_set_flags, EC_KEY_clear_flags,
8EC_KEY_new_by_curve_name_ex, EC_KEY_new_by_curve_name, EC_KEY_free,
9EC_KEY_copy, EC_KEY_dup, EC_KEY_up_ref, EC_KEY_get0_engine,
10EC_KEY_get0_group, EC_KEY_set_group, EC_KEY_get0_private_key,
11EC_KEY_set_private_key, EC_KEY_get0_public_key, EC_KEY_set_public_key,
12EC_KEY_get_conv_form,
13EC_KEY_set_conv_form, EC_KEY_set_asn1_flag,
14EC_KEY_decoded_from_explicit_params, EC_KEY_precompute_mult,
15EC_KEY_generate_key, EC_KEY_check_key, EC_KEY_set_public_key_affine_coordinates,
16EC_KEY_oct2key, EC_KEY_key2buf, EC_KEY_oct2priv, EC_KEY_priv2oct,
17EC_KEY_priv2buf - Functions for creating, destroying and manipulating
18EC_KEY objects
19
20=head1 SYNOPSIS
21
22 #include <openssl/ec.h>
23
24 EVP_PKEY *EVP_EC_gen(const char *curve);
25
26The following functions have been deprecated since OpenSSL 3.0, and can be
27hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
28see L<openssl_user_macros(7)>:
29
30 EC_KEY *EC_KEY_new_ex(OSSL_LIB_CTX *ctx, const char *propq);
31 EC_KEY *EC_KEY_new(void);
32 int EC_KEY_get_flags(const EC_KEY *key);
33 void EC_KEY_set_flags(EC_KEY *key, int flags);
34 void EC_KEY_clear_flags(EC_KEY *key, int flags);
35 EC_KEY *EC_KEY_new_by_curve_name_ex(OSSL_LIB_CTX *ctx, const char *propq,
36                                     int nid);
37 EC_KEY *EC_KEY_new_by_curve_name(int nid);
38 void EC_KEY_free(EC_KEY *key);
39 EC_KEY *EC_KEY_copy(EC_KEY *dst, const EC_KEY *src);
40 EC_KEY *EC_KEY_dup(const EC_KEY *src);
41 int EC_KEY_up_ref(EC_KEY *key);
42 ENGINE *EC_KEY_get0_engine(const EC_KEY *eckey);
43 const EC_GROUP *EC_KEY_get0_group(const EC_KEY *key);
44 int EC_KEY_set_group(EC_KEY *key, const EC_GROUP *group);
45 const BIGNUM *EC_KEY_get0_private_key(const EC_KEY *key);
46 int EC_KEY_set_private_key(EC_KEY *key, const BIGNUM *priv_key);
47 const EC_POINT *EC_KEY_get0_public_key(const EC_KEY *key);
48 int EC_KEY_set_public_key(EC_KEY *key, const EC_POINT *pub);
49 point_conversion_form_t EC_KEY_get_conv_form(const EC_KEY *key);
50 void EC_KEY_set_conv_form(EC_KEY *eckey, point_conversion_form_t cform);
51 void EC_KEY_set_asn1_flag(EC_KEY *eckey, int asn1_flag);
52 int EC_KEY_decoded_from_explicit_params(const EC_KEY *key);
53 int EC_KEY_generate_key(EC_KEY *key);
54 int EC_KEY_check_key(const EC_KEY *key);
55 int EC_KEY_set_public_key_affine_coordinates(EC_KEY *key, BIGNUM *x, BIGNUM *y);
56 const EC_KEY_METHOD *EC_KEY_get_method(const EC_KEY *key);
57 int EC_KEY_set_method(EC_KEY *key, const EC_KEY_METHOD *meth);
58
59 int EC_KEY_oct2key(EC_KEY *eckey, const unsigned char *buf, size_t len, BN_CTX *ctx);
60 size_t EC_KEY_key2buf(const EC_KEY *eckey, point_conversion_form_t form,
61                       unsigned char **pbuf, BN_CTX *ctx);
62
63 int EC_KEY_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len);
64 size_t EC_KEY_priv2oct(const EC_KEY *eckey, unsigned char *buf, size_t len);
65
66 size_t EC_KEY_priv2buf(const EC_KEY *eckey, unsigned char **pbuf);
67 int EC_KEY_precompute_mult(EC_KEY *key, BN_CTX *ctx);
68
69=head1 DESCRIPTION
70
71EVP_EC_gen() generates a new EC key pair on the given I<curve>.
72
73All of the functions described below are deprecated.
74Applications should instead use EVP_EC_gen(), L<EVP_PKEY_Q_keygen(3)>, or
75L<EVP_PKEY_keygen_init(3)> and L<EVP_PKEY_keygen(3)>.
76
77An EC_KEY represents a public key and, optionally, the associated private
78key.
79A new EC_KEY with no associated curve can be constructed by calling
80EC_KEY_new_ex() and specifying the associated library context in I<ctx>
81(see L<OSSL_LIB_CTX(3)>) and property query string I<propq>.
82The I<ctx> parameter may be NULL in which case the default library context is
83used.
84The reference count for the newly created EC_KEY is initially
85set to 1.
86A curve can be associated with the EC_KEY by calling
87EC_KEY_set_group().
88
89EC_KEY_new() is the same as EC_KEY_new_ex() except that the default library
90context is always used.
91
92Alternatively a new EC_KEY can be constructed by calling
93EC_KEY_new_by_curve_name_ex() and supplying the nid of the associated
94curve, the library context to be used I<ctx> (see L<OSSL_LIB_CTX(3)>) and any
95property query string I<propq>.
96The I<ctx> parameter may be NULL in which case the default library context is
97used. The I<propq> value may also be NULL.
98See L<EC_GROUP_new(3)> for a description of curve names.
99This function simply wraps calls to EC_KEY_new_ex() and
100EC_GROUP_new_by_curve_name_ex().
101
102EC_KEY_new_by_curve_name() is the same as EC_KEY_new_by_curve_name_ex()
103except that the default library context is always used and a NULL property query
104string.
105
106Calling EC_KEY_free() decrements the reference count for the EC_KEY object,
107and if it has dropped to zero then frees the memory associated with it.  If
108I<key> is NULL nothing is done.
109
110EC_KEY_copy() copies the contents of the EC_KEY in I<src> into I<dest>.
111
112EC_KEY_dup() creates a new EC_KEY object and copies I<ec_key> into it.
113
114EC_KEY_up_ref() increments the reference count associated with the EC_KEY
115object.
116
117EC_KEY_get0_engine() returns a handle to the ENGINE that has been set for
118this EC_KEY object.
119
120EC_KEY_generate_key() generates a new public and private key for the supplied
121I<eckey> object. I<eckey> must have an EC_GROUP object associated with it
122before calling this function. The private key is a random integer (0 < priv_key
123< order, where I<order> is the order of the EC_GROUP object). The public key is
124an EC_POINT on the curve calculated by multiplying the generator for the
125curve by the private key.
126
127EC_KEY_check_key() performs various sanity checks on the EC_KEY object to
128confirm that it is valid.
129
130EC_KEY_set_public_key_affine_coordinates() sets the public key for I<key> based
131on its affine coordinates; i.e., it constructs an EC_POINT object based on
132the supplied I<x> and I<y> values and sets the public key to be this
133EC_POINT. It also performs certain sanity checks on the key to confirm
134that it is valid.
135
136The functions EC_KEY_get0_group(), EC_KEY_set_group(),
137EC_KEY_get0_private_key(), EC_KEY_set_private_key(), EC_KEY_get0_public_key(),
138and EC_KEY_set_public_key() get and set the EC_GROUP object, the private key,
139and the EC_POINT public key for the B<key> respectively. The function
140EC_KEY_set_private_key() accepts NULL as the priv_key argument to securely clear
141the private key component from the EC_KEY.
142
143The functions EC_KEY_get_conv_form() and EC_KEY_set_conv_form() get and set the
144point_conversion_form for the I<key>. For a description of
145point_conversion_forms please see L<EC_POINT_new(3)>.
146
147EC_KEY_set_flags() sets the flags in the I<flags> parameter on the EC_KEY
148object. Any flags that are already set are left set. The flags currently
149defined are EC_FLAG_NON_FIPS_ALLOW and EC_FLAG_FIPS_CHECKED. In
150addition there is the flag EC_FLAG_COFACTOR_ECDH which is specific to ECDH.
151EC_KEY_get_flags() returns the current flags that are set for this EC_KEY.
152EC_KEY_clear_flags() clears the flags indicated by the I<flags> parameter; all
153other flags are left in their existing state.
154
155EC_KEY_set_asn1_flag() sets the asn1_flag on the underlying EC_GROUP object
156(if set). Refer to L<EC_GROUP_copy(3)> for further information on the
157asn1_flag.
158
159EC_KEY_decoded_from_explicit_params() returns 1 if the group of the I<key> was
160decoded from data with explicitly encoded group parameters, -1 if the I<key>
161is NULL or the group parameters are missing, and 0 otherwise.
162
163EC_KEY_precompute_mult() stores multiples of the underlying EC_GROUP generator
164for faster point multiplication. See also L<EC_POINT_add(3)>.
165Modern versions should instead switch to named curves which OpenSSL has
166hardcoded lookup tables for.
167
168EC_KEY_oct2key() and EC_KEY_key2buf() are identical to the functions
169EC_POINT_oct2point() and EC_POINT_point2buf() except they use the public key
170EC_POINT in I<eckey>.
171
172EC_KEY_oct2priv() and EC_KEY_priv2oct() convert between the private key
173component of I<eckey> and octet form. The octet form consists of the content
174octets of the I<privateKey> OCTET STRING in an I<ECPrivateKey> ASN.1 structure.
175
176The function EC_KEY_priv2oct() must be supplied with a buffer long enough to
177store the octet form. The return value provides the number of octets stored.
178Calling the function with a NULL buffer will not perform the conversion but
179will just return the required buffer length.
180
181The function EC_KEY_priv2buf() allocates a buffer of suitable length and writes
182an EC_KEY to it in octet format. The allocated buffer is written to I<*pbuf>
183and its length is returned. The caller must free up the allocated buffer with a
184call to OPENSSL_free(). Since the allocated buffer value is written to I<*pbuf>
185the I<pbuf> parameter B<MUST NOT> be B<NULL>.
186
187EC_KEY_priv2buf() converts an EC_KEY private key into an allocated buffer.
188
189=head1 RETURN VALUES
190
191EC_KEY_new_ex(), EC_KEY_new(), EC_KEY_new_by_curve_name_ex(),
192EC_KEY_new_by_curve_name() and EC_KEY_dup() return a pointer to the newly
193created EC_KEY object, or NULL on error.
194
195EC_KEY_get_flags() returns the flags associated with the EC_KEY object as an
196integer.
197
198EC_KEY_copy() returns a pointer to the destination key, or NULL on error.
199
200EC_KEY_get0_engine() returns a pointer to an ENGINE, or NULL if it wasn't set.
201
202EC_KEY_up_ref(), EC_KEY_set_group(), EC_KEY_set_public_key(),
203EC_KEY_precompute_mult(), EC_KEY_generate_key(), EC_KEY_check_key(),
204EC_KEY_set_public_key_affine_coordinates(), EC_KEY_oct2key() and
205EC_KEY_oct2priv() return 1 on success or 0 on error.
206
207EC_KEY_set_private_key() returns 1 on success or 0 on error except when the
208priv_key argument is NULL, in that case it returns 0, for legacy compatibility,
209and should not be treated as an error.
210
211EC_KEY_get0_group() returns the EC_GROUP associated with the EC_KEY.
212
213EC_KEY_get0_private_key() returns the private key associated with the EC_KEY.
214
215EC_KEY_get_conv_form() return the point_conversion_form for the EC_KEY.
216
217EC_KEY_key2buf(), EC_KEY_priv2oct() and EC_KEY_priv2buf() return the length
218of the buffer or 0 on error.
219
220=head1 SEE ALSO
221
222L<EVP_PKEY_Q_keygen(3)>
223L<crypto(7)>, L<EC_GROUP_new(3)>,
224L<EC_GROUP_copy(3)>, L<EC_POINT_new(3)>,
225L<EC_POINT_add(3)>,
226L<EC_GFp_simple_method(3)>,
227L<d2i_ECPKParameters(3)>,
228L<OSSL_LIB_CTX(3)>
229
230=head1 HISTORY
231
232EVP_EC_gen() was added in OpenSSL 3.0.
233All other functions described here were deprecated in OpenSSL 3.0.
234For replacement see L<EVP_PKEY-EC(7)>.
235
236=head1 COPYRIGHT
237
238Copyright 2013-2023 The OpenSSL Project Authors. All Rights Reserved.
239
240Licensed under the Apache License 2.0 (the "License").  You may not use
241this file except in compliance with the License.  You can obtain a copy
242in the file LICENSE in the source distribution or at
243L<https://www.openssl.org/source/license.html>.
244
245=cut
246