6 EVP_PKEY_keygen_init, EVP_PKEY_paramgen_init, EVP_PKEY_generate,
7 EVP_PKEY_CTX_set_cb, EVP_PKEY_CTX_get_cb,
8 EVP_PKEY_CTX_get_keygen_info, EVP_PKEY_CTX_set_app_data,
9 EVP_PKEY_CTX_get_app_data,
11 EVP_PKEY_paramgen, EVP_PKEY_keygen
12 - key and parameter generation and check functions
16 #include <openssl/evp.h>
18 EVP_PKEY *EVP_PKEY_Q_keygen(OSSL_LIB_CTX *libctx, const char *propq,
19 const char *type, ...);
21 int EVP_PKEY_keygen_init(EVP_PKEY_CTX *ctx);
22 int EVP_PKEY_paramgen_init(EVP_PKEY_CTX *ctx);
23 int EVP_PKEY_generate(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey);
24 int EVP_PKEY_paramgen(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey);
25 int EVP_PKEY_keygen(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey);
27 typedef int EVP_PKEY_gen_cb(EVP_PKEY_CTX *ctx);
29 void EVP_PKEY_CTX_set_cb(EVP_PKEY_CTX *ctx, EVP_PKEY_gen_cb *cb);
30 EVP_PKEY_gen_cb *EVP_PKEY_CTX_get_cb(EVP_PKEY_CTX *ctx);
32 int EVP_PKEY_CTX_get_keygen_info(EVP_PKEY_CTX *ctx, int idx);
34 void EVP_PKEY_CTX_set_app_data(EVP_PKEY_CTX *ctx, void *data);
35 void *EVP_PKEY_CTX_get_app_data(EVP_PKEY_CTX *ctx);
39 Generating keys is sometimes straight forward, just generate the key's
40 numbers and be done with it. However, there are certain key types that need
41 key parameters, often called domain parameters but not necessarily limited
42 to that, that also need to be generated. In addition to this, the caller
43 may want to set user provided generation parameters that further affect key
44 parameter or key generation, such as the desired key size.
46 To flexibly allow all that's just been described, key parameter and key
47 generation is divided into an initialization of a key algorithm context,
48 functions to set user provided parameters, and finally the key parameter or
49 key generation function itself.
51 The key algorithm context must be created using L<EVP_PKEY_CTX_new(3)> or
52 variants thereof, see that manual for details.
54 EVP_PKEY_keygen_init() initializes a public key algorithm context I<ctx>
55 for a key generation operation.
57 EVP_PKEY_paramgen_init() is similar to EVP_PKEY_keygen_init() except key
58 parameters are generated.
60 After initialization, generation parameters may be provided with
61 L<EVP_PKEY_CTX_ctrl(3)> or L<EVP_PKEY_CTX_set_params(3)>, or any other
62 function described in those manuals.
64 EVP_PKEY_generate() performs the generation operation, the resulting key
65 parameters or key are written to I<*ppkey>. If I<*ppkey> is NULL when this
66 function is called, it will be allocated, and should be freed by the caller
67 when no longer useful, using L<EVP_PKEY_free(3)>.
69 EVP_PKEY_paramgen() and EVP_PKEY_keygen() do exactly the same thing as
70 EVP_PKEY_generate(), after checking that the corresponding EVP_PKEY_paramgen_init()
71 or EVP_PKEY_keygen_init() was used to initialize I<ctx>.
72 These are older functions that are kept for backward compatibility.
73 It is safe to use EVP_PKEY_generate() instead.
75 The function EVP_PKEY_set_cb() sets the key or parameter generation callback
76 to I<cb>. The function EVP_PKEY_CTX_get_cb() returns the key or parameter
79 The function EVP_PKEY_CTX_get_keygen_info() returns parameters associated
80 with the generation operation. If I<idx> is -1 the total number of
81 parameters available is returned. Any non negative value returns the value of
82 that parameter. EVP_PKEY_CTX_gen_keygen_info() with a nonnegative value for
83 I<idx> should only be called within the generation callback.
85 If the callback returns 0 then the key generation operation is aborted and an
86 error occurs. This might occur during a time consuming operation where
87 a user clicks on a "cancel" button.
89 The functions EVP_PKEY_CTX_set_app_data() and EVP_PKEY_CTX_get_app_data() set
90 and retrieve an opaque pointer. This can be used to set some application
91 defined value which can be retrieved in the callback: for example a handle
92 which is used to update a "progress dialog".
94 EVP_PKEY_Q_keygen() abstracts from the explicit use of B<EVP_PKEY_CTX> while
95 providing a 'quick' but limited way of generating a new asymmetric key pair.
96 It provides shorthands for simple and common cases of key generation.
97 As usual, the library context I<libctx> and property query I<propq>
98 can be given for fetching algorithms from providers.
100 a B<size_t> parameter must be given to specify the size of the RSA key.
102 a string parameter must be given to specify the name of the EC curve.
103 If I<type> is C<X25519>, C<X448>, C<ED25519>, or C<ED448>
104 no further parameter is needed.
108 EVP_PKEY_keygen_init(), EVP_PKEY_paramgen_init(), EVP_PKEY_keygen() and
109 EVP_PKEY_paramgen() return 1 for success and 0 or a negative value for failure.
110 In particular a return value of -2 indicates the operation is not supported by
111 the public key algorithm.
113 EVP_PKEY_Q_keygen() returns an B<EVP_PKEY>, or NULL on failure.
117 After the call to EVP_PKEY_keygen_init() or EVP_PKEY_paramgen_init() algorithm
118 specific control operations can be performed to set any appropriate parameters
121 The functions EVP_PKEY_keygen() and EVP_PKEY_paramgen() can be called more than
122 once on the same context if several operations are performed using the same
125 The meaning of the parameters passed to the callback will depend on the
126 algorithm and the specific implementation of the algorithm. Some might not
127 give any useful information at all during key or parameter generation. Others
128 might not even call the callback.
130 The operation performed by key or parameter generation depends on the algorithm
131 used. In some cases (e.g. EC with a supplied named curve) the "generation"
132 option merely sets the appropriate fields in an EVP_PKEY structure.
134 In OpenSSL an EVP_PKEY structure containing a private key also contains the
135 public key components and parameters (if any). An OpenSSL private key is
136 equivalent to what some libraries call a "key pair". A private key can be used
137 in functions which require the use of a public key or parameters.
141 Generate a 2048 bit RSA key:
143 #include <openssl/evp.h>
144 #include <openssl/rsa.h>
147 EVP_PKEY *pkey = NULL;
149 ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL);
152 if (EVP_PKEY_keygen_init(ctx) <= 0)
154 if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 2048) <= 0)
158 if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
161 Generate a key from a set of parameters:
163 #include <openssl/evp.h>
164 #include <openssl/rsa.h>
168 EVP_PKEY *pkey = NULL, *param;
170 /* Assumed param, eng are set up already */
171 ctx = EVP_PKEY_CTX_new(param, eng);
174 if (EVP_PKEY_keygen_init(ctx) <= 0)
178 if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
181 Example of generation callback for OpenSSL public key implementations:
183 /* Application data is a BIO to output status to */
185 EVP_PKEY_CTX_set_app_data(ctx, status_bio);
187 static int genpkey_cb(EVP_PKEY_CTX *ctx)
190 BIO *b = EVP_PKEY_CTX_get_app_data(ctx);
191 int p = EVP_PKEY_CTX_get_keygen_info(ctx, 0);
208 L<EVP_RSA_gen(3)>, L<EVP_EC_gen(3)>,
209 L<EVP_PKEY_CTX_new(3)>,
210 L<EVP_PKEY_encrypt(3)>,
211 L<EVP_PKEY_decrypt(3)>,
213 L<EVP_PKEY_verify(3)>,
214 L<EVP_PKEY_verify_recover(3)>,
215 L<EVP_PKEY_derive(3)>
219 EVP_PKEY_keygen_init(), int EVP_PKEY_paramgen_init(), EVP_PKEY_keygen(),
220 EVP_PKEY_paramgen(), EVP_PKEY_gen_cb(), EVP_PKEY_CTX_set_cb(),
221 EVP_PKEY_CTX_get_cb(), EVP_PKEY_CTX_get_keygen_info(),
222 EVP_PKEY_CTX_set_app_data() and EVP_PKEY_CTX_get_app_data() were added in
225 EVP_PKEY_Q_keygen() and EVP_PKEY_generate() were added in OpenSSL 3.0.
229 Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved.
231 Licensed under the Apache License 2.0 (the "License"). You may not use
232 this file except in compliance with the License. You can obtain a copy
233 in the file LICENSE in the source distribution or at
234 L<https://www.openssl.org/source/license.html>.