xref: /openssl/doc/man3/EVP_PKEY_new.pod (revision fecb3aae) 
1=pod
2
3=head1 NAME
4
5EVP_PKEY,
6EVP_PKEY_new,
7EVP_PKEY_up_ref,
8EVP_PKEY_dup,
9EVP_PKEY_free,
10EVP_PKEY_new_raw_private_key_ex,
11EVP_PKEY_new_raw_private_key,
12EVP_PKEY_new_raw_public_key_ex,
13EVP_PKEY_new_raw_public_key,
14EVP_PKEY_new_CMAC_key,
15EVP_PKEY_new_mac_key,
16EVP_PKEY_get_raw_private_key,
17EVP_PKEY_get_raw_public_key
18- public/private key allocation and raw key handling functions
19
20=head1 SYNOPSIS
21
22 #include <openssl/evp.h>
23
24 typedef evp_pkey_st EVP_PKEY;
25
26 EVP_PKEY *EVP_PKEY_new(void);
27 int EVP_PKEY_up_ref(EVP_PKEY *key);
28 EVP_PKEY *EVP_PKEY_dup(EVP_PKEY *key);
29 void EVP_PKEY_free(EVP_PKEY *key);
30
31 EVP_PKEY *EVP_PKEY_new_raw_private_key_ex(OSSL_LIB_CTX *libctx,
32                                           const char *keytype,
33                                           const char *propq,
34                                           const unsigned char *key,
35                                           size_t keylen);
36 EVP_PKEY *EVP_PKEY_new_raw_private_key(int type, ENGINE *e,
37                                        const unsigned char *key, size_t keylen);
38 EVP_PKEY *EVP_PKEY_new_raw_public_key_ex(OSSL_LIB_CTX *libctx,
39                                          const char *keytype,
40                                          const char *propq,
41                                          const unsigned char *key,
42                                          size_t keylen);
43 EVP_PKEY *EVP_PKEY_new_raw_public_key(int type, ENGINE *e,
44                                       const unsigned char *key, size_t keylen);
45 EVP_PKEY *EVP_PKEY_new_mac_key(int type, ENGINE *e, const unsigned char *key,
46                                int keylen);
47
48 int EVP_PKEY_get_raw_private_key(const EVP_PKEY *pkey, unsigned char *priv,
49                                  size_t *len);
50 int EVP_PKEY_get_raw_public_key(const EVP_PKEY *pkey, unsigned char *pub,
51                                 size_t *len);
52
53The following function has been deprecated since OpenSSL 3.0, and can be
54hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
55see L<openssl_user_macros(7)>:
56
57 EVP_PKEY *EVP_PKEY_new_CMAC_key(ENGINE *e, const unsigned char *priv,
58                                 size_t len, const EVP_CIPHER *cipher);
59
60=head1 DESCRIPTION
61
62B<EVP_PKEY> is a generic structure to hold diverse types of asymmetric keys
63(also known as "key pairs"), and can be used for diverse operations, like
64signing, verifying signatures, key derivation, etc.  The asymmetric keys
65themselves are often referred to as the "internal key", and are handled by
66backends, such as providers (through L<EVP_KEYMGMT(3)>) or B<ENGINE>s.
67
68Conceptually, an B<EVP_PKEY> internal key may hold a private key, a public
69key, or both (a keypair), and along with those, key parameters if the key type
70requires them.  The presence of these components determine what operations can
71be made; for example, signing normally requires the presence of a private key,
72and verifying normally requires the presence of a public key.
73
74=for comment ED signature require both the private and public key...
75
76B<EVP_PKEY> has also been used for MAC algorithm that were conceived as
77producing signatures, although not being public key algorithms; "POLY1305",
78"SIPHASH", "HMAC", "CMAC".  This usage is considered legacy and is discouraged
79in favor of the L<EVP_MAC(3)> API.
80
81The EVP_PKEY_new() function allocates an empty B<EVP_PKEY> structure which is
82used by OpenSSL to store public and private keys. The reference count is set to
83B<1>.
84
85EVP_PKEY_up_ref() increments the reference count of I<key>.
86
87EVP_PKEY_dup() duplicates the I<key>. The I<key> must not be ENGINE based or
88a raw key, otherwise the duplication will fail.
89
90EVP_PKEY_free() decrements the reference count of I<key> and, if the reference
91count is zero, frees it up. If I<key> is NULL, nothing is done.
92
93EVP_PKEY_new_raw_private_key_ex() allocates a new B<EVP_PKEY>. Unless an
94engine should be used for the key type, a provider for the key is found using
95the library context I<libctx> and the property query string I<propq>. The
96I<keytype> argument indicates what kind of key this is. The value should be a
97string for a public key algorithm that supports raw private keys, i.e one of
98"X25519", "ED25519", "X448" or "ED448". I<key> points to the raw private key
99data for this B<EVP_PKEY> which should be of length I<keylen>. The length
100should be appropriate for the type of the key. The public key data will be
101automatically derived from the given private key data (if appropriate for the
102algorithm type).
103
104EVP_PKEY_new_raw_private_key() does the same as
105EVP_PKEY_new_raw_private_key_ex() except that the default library context and
106default property query are used instead. If I<e> is non-NULL then the new
107B<EVP_PKEY> structure is associated with the engine I<e>. The I<type> argument
108indicates what kind of key this is. The value should be a NID for a public key
109algorithm that supports raw private keys, i.e. one of B<EVP_PKEY_X25519>,
110B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or B<EVP_PKEY_ED448>.
111
112EVP_PKEY_new_raw_private_key_ex() and EVP_PKEY_new_raw_private_key() may also
113be used with most MACs implemented as public key algorithms, so key types such
114as "HMAC", "POLY1305", "SIPHASH", or their NID form B<EVP_PKEY_POLY1305>,
115B<EVP_PKEY_SIPHASH>, B<EVP_PKEY_HMAC> are also accepted.  This usage is,
116as mentioned above, discouraged in favor of the L<EVP_MAC(3)> API.
117
118EVP_PKEY_new_raw_public_key_ex() works in the same way as
119EVP_PKEY_new_raw_private_key_ex() except that I<key> points to the raw
120public key data. The B<EVP_PKEY> structure will be initialised without any
121private key information. Algorithm types that support raw public keys are
122"X25519", "ED25519", "X448" or "ED448".
123
124EVP_PKEY_new_raw_public_key() works in the same way as
125EVP_PKEY_new_raw_private_key() except that I<key> points to the raw public key
126data. The B<EVP_PKEY> structure will be initialised without any private key
127information. Algorithm types that support raw public keys are
128B<EVP_PKEY_X25519>, B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or B<EVP_PKEY_ED448>.
129
130EVP_PKEY_new_mac_key() works in the same way as EVP_PKEY_new_raw_private_key().
131New applications should use EVP_PKEY_new_raw_private_key() instead.
132
133EVP_PKEY_get_raw_private_key() fills the buffer provided by I<priv> with raw
134private key data. The size of the I<priv> buffer should be in I<*len> on entry
135to the function, and on exit I<*len> is updated with the number of bytes
136actually written. If the buffer I<priv> is NULL then I<*len> is populated with
137the number of bytes required to hold the key. The calling application is
138responsible for ensuring that the buffer is large enough to receive the private
139key data. This function only works for algorithms that support raw private keys.
140Currently this is: B<EVP_PKEY_HMAC>, B<EVP_PKEY_POLY1305>, B<EVP_PKEY_SIPHASH>,
141B<EVP_PKEY_X25519>, B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or B<EVP_PKEY_ED448>.
142
143EVP_PKEY_get_raw_public_key() fills the buffer provided by I<pub> with raw
144public key data. The size of the I<pub> buffer should be in I<*len> on entry
145to the function, and on exit I<*len> is updated with the number of bytes
146actually written. If the buffer I<pub> is NULL then I<*len> is populated with
147the number of bytes required to hold the key. The calling application is
148responsible for ensuring that the buffer is large enough to receive the public
149key data. This function only works for algorithms that support raw public  keys.
150Currently this is: B<EVP_PKEY_X25519>, B<EVP_PKEY_ED25519>, B<EVP_PKEY_X448> or
151B<EVP_PKEY_ED448>.
152
153EVP_PKEY_new_CMAC_key() works in the same way as EVP_PKEY_new_raw_private_key()
154except it is only for the B<EVP_PKEY_CMAC> algorithm type. In addition to the
155raw private key data, it also takes a cipher algorithm to be used during
156creation of a CMAC in the B<cipher> argument. The cipher should be a standard
157encryption-only cipher. For example AEAD and XTS ciphers should not be used.
158
159Applications should use the L<EVP_MAC(3)> API instead
160and set the B<OSSL_MAC_PARAM_CIPHER> parameter on the B<EVP_MAC_CTX> object
161with the name of the cipher being used.
162
163=head1 NOTES
164
165The B<EVP_PKEY> structure is used by various OpenSSL functions which require a
166general private key without reference to any particular algorithm.
167
168The structure returned by EVP_PKEY_new() is empty. To add a private or public
169key to this empty structure use the appropriate functions described in
170L<EVP_PKEY_set1_RSA(3)>, L<EVP_PKEY_set1_DSA(3)>, L<EVP_PKEY_set1_DH(3)> or
171L<EVP_PKEY_set1_EC_KEY(3)>.
172
173=head1 RETURN VALUES
174
175EVP_PKEY_new(), EVP_PKEY_new_raw_private_key(), EVP_PKEY_new_raw_public_key(),
176EVP_PKEY_new_CMAC_key() and EVP_PKEY_new_mac_key() return either the newly
177allocated B<EVP_PKEY> structure or NULL if an error occurred.
178
179EVP_PKEY_dup() returns the key duplicate or NULL if an error occurred.
180
181EVP_PKEY_up_ref(), EVP_PKEY_get_raw_private_key() and
182EVP_PKEY_get_raw_public_key() return 1 for success and 0 for failure.
183
184=head1 SEE ALSO
185
186L<EVP_PKEY_set1_RSA(3)>, L<EVP_PKEY_set1_DSA(3)>, L<EVP_PKEY_set1_DH(3)> or
187L<EVP_PKEY_set1_EC_KEY(3)>
188
189=head1 HISTORY
190
191The
192EVP_PKEY_new() and EVP_PKEY_free() functions exist in all versions of OpenSSL.
193
194The EVP_PKEY_up_ref() function was added in OpenSSL 1.1.0.
195
196The
197EVP_PKEY_new_raw_private_key(), EVP_PKEY_new_raw_public_key(),
198EVP_PKEY_new_CMAC_key(), EVP_PKEY_new_raw_private_key() and
199EVP_PKEY_get_raw_public_key() functions were added in OpenSSL 1.1.1.
200
201The EVP_PKEY_dup(), EVP_PKEY_new_raw_private_key_ex(), and
202EVP_PKEY_new_raw_public_key_ex()
203functions were added in OpenSSL 3.0.
204
205The EVP_PKEY_new_CMAC_key() was deprecated in OpenSSL 3.0.
206
207The documentation of B<EVP_PKEY> was amended in OpenSSL 3.0 to allow there to
208be the private part of the keypair without the public part, where this was
209previously implied to be disallowed.
210
211=head1 COPYRIGHT
212
213Copyright 2002-2022 The OpenSSL Project Authors. All Rights Reserved.
214
215Licensed under the Apache License 2.0 (the "License").  You may not use
216this file except in compliance with the License.  You can obtain a copy
217in the file LICENSE in the source distribution or at
218L<https://www.openssl.org/source/license.html>.
219
220=cut
221