.\" $OpenBSD: EVP_PKEY_keygen.3,v 1.10 2022/11/16 15:34:41 schwarze Exp $ .\" full merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100 .\" selective merge up to: OpenSSL 48e5119a Jan 19 10:49:22 2018 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2006, 2009, 2013, 2015, 2016, 2018 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: November 16 2022 $ .Dt EVP_PKEY_KEYGEN 3 .Os .Sh NAME .Nm EVP_PKEY_keygen_init , .Nm EVP_PKEY_keygen , .Nm EVP_PKEY_paramgen_init , .Nm EVP_PKEY_paramgen , .Nm EVP_PKEY_gen_cb , .Nm EVP_PKEY_CTX_set_cb , .Nm EVP_PKEY_CTX_get_cb , .Nm EVP_PKEY_CTX_get_keygen_info , .Nm EVP_PKEY_CTX_set_app_data , .Nm EVP_PKEY_CTX_get_app_data .\" The following functions are intentionally undocumented: .\" .Nm BN_X931_derive_prime_ex , .\" .Nm BN_X931_generate_prime_ex , .\" .Nm BN_X931_generate_Xpq .\" They are unused outside OpenSSL/LibreSSL and deprecated in OpenSSL 3.0, .\" see https://github.com/openssl/openssl/issues/10111 .Nd key and parameter generation functions .Sh SYNOPSIS .In openssl/evp.h .Ft int .Fo EVP_PKEY_keygen_init .Fa "EVP_PKEY_CTX *ctx" .Fc .Ft int .Fo EVP_PKEY_keygen .Fa "EVP_PKEY_CTX *ctx" .Fa "EVP_PKEY **ppkey" .Fc .Ft int .Fo EVP_PKEY_paramgen_init .Fa "EVP_PKEY_CTX *ctx" .Fc .Ft int .Fo EVP_PKEY_paramgen .Fa "EVP_PKEY_CTX *ctx" .Fa "EVP_PKEY **ppkey" .Fc .Ft typedef int .Fo EVP_PKEY_gen_cb .Fa "EVP_PKEY_CTX *ctx" .Fc .Ft void .Fo EVP_PKEY_CTX_set_cb .Fa "EVP_PKEY_CTX *ctx" .Fa "EVP_PKEY_gen_cb *cb" .Fc .Ft EVP_PKEY_gen_cb * .Fo EVP_PKEY_CTX_get_cb .Fa "EVP_PKEY_CTX *ctx" .Fc .Ft int .Fo EVP_PKEY_CTX_get_keygen_info .Fa "EVP_PKEY_CTX *ctx" .Fa "int idx" .Fc .Ft void .Fo EVP_PKEY_CTX_set_app_data .Fa "EVP_PKEY_CTX *ctx" .Fa "void *data" .Fc .Ft void * .Fo EVP_PKEY_CTX_get_app_data .Fa "EVP_PKEY_CTX *ctx" .Fc .Sh DESCRIPTION The .Fn EVP_PKEY_keygen_init function initializes a public key algorithm context using key .Fa ctx->pkey for a key generation operation. .Pp The .Fn EVP_PKEY_keygen function performs a key generation operation. The generated key is written to .Fa ppkey . .Pp The functions .Fn EVP_PKEY_paramgen_init and .Fn EVP_PKEY_paramgen are similar except parameters are generated. .Pp The function .Fn EVP_PKEY_CTX_set_cb sets the key or parameter generation callback to .Fa cb . The function .Fn EVP_PKEY_CTX_get_cb returns the key or parameter generation callback. .Pp The function .Fn EVP_PKEY_CTX_get_keygen_info returns parameters associated with the generation operation. If .Fa idx is -1, the total number of parameters available is returned. Any non-negative value returns the value of that parameter. .Fn EVP_PKEY_CTX_get_keygen_info with a non-negative value for .Fa idx should only be called within the generation callback. .Pp If the callback returns 0, then the key generation operation is aborted and an error occurs. This might occur during a time consuming operation where a user clicks on a "cancel" button. .Pp The functions .Fn EVP_PKEY_CTX_set_app_data and .Fn EVP_PKEY_CTX_get_app_data set and retrieve an opaque pointer. This can be used to set some application defined value which can be retrieved in the callback: for example a handle which is used to update a "progress dialog". .Pp After the call to .Fn EVP_PKEY_keygen_init or .Fn EVP_PKEY_paramgen_init , algorithm specific control operations can be performed to set any appropriate parameters for the operation. .Pp The functions .Fn EVP_PKEY_keygen and .Fn EVP_PKEY_paramgen can be called more than once on the same context if several operations are performed using the same parameters. .Pp The meaning of the parameters passed to the callback will depend on the algorithm and the specific implementation of the algorithm. Some might not give any useful information at all during key or parameter generation. Others might not even call the callback. .Pp The operation performed by key or parameter generation depends on the algorithm used. In some cases (e.g. EC with a supplied named curve) the "generation" option merely sets the appropriate fields in an .Vt EVP_PKEY structure. .Pp In OpenSSL, an .Vt EVP_PKEY structure containing a private key also contains the public key components and parameters (if any). An OpenSSL private key is equivalent to what some libraries call a "key pair". A private key can be used in functions which require the use of a public key or parameters. .Sh RETURN VALUES .Fn EVP_PKEY_keygen_init , .Fn EVP_PKEY_paramgen_init , .Fn EVP_PKEY_keygen , and .Fn EVP_PKEY_paramgen return 1 for success and 0 or a negative value for failure. In particular, a return value of -2 indicates the operation is not supported by the public key algorithm. .Sh EXAMPLES Generate a 2048-bit RSA key: .Bd -literal -offset indent #include #include EVP_PKEY_CTX *ctx; EVP_PKEY *pkey = NULL; ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL); if (!ctx) /* Error occurred */ if (EVP_PKEY_keygen_init(ctx) <= 0) /* Error */ if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 2048) <= 0) /* Error */ /* Generate key */ if (EVP_PKEY_keygen(ctx, &pkey) <= 0) /* Error */ .Ed .Pp Generate a key from a set of parameters: .Bd -literal -offset indent #include #include EVP_PKEY_CTX *ctx; ENGINE *eng; EVP_PKEY *pkey = NULL, *param; /* Assumes that param and eng are already set up. */ ctx = EVP_PKEY_CTX_new(param, eng); if (!ctx) /* Error occurred */ if (EVP_PKEY_keygen_init(ctx) <= 0) /* Error */ /* Generate key */ if (EVP_PKEY_keygen(ctx, &pkey) <= 0) /* Error */ .Ed .Pp Example of generation callback for OpenSSL public key implementations: .Bd -literal -offset indent /* Application data is a BIO to output status to */ EVP_PKEY_CTX_set_app_data(ctx, status_bio); static int genpkey_cb(EVP_PKEY_CTX *ctx) { char c = '*'; BIO *b = EVP_PKEY_CTX_get_app_data(ctx); int p; p = EVP_PKEY_CTX_get_keygen_info(ctx, 0); if (p == 0) c = '.'; if (p == 1) c = '+'; if (p == 2) c = '*'; if (p == 3) c = '\en'; BIO_write(b, &c, 1); (void)BIO_flush(b); return 1; } .Ed .Sh SEE ALSO .Xr EVP_PKEY_CTX_new 3 , .Xr EVP_PKEY_decrypt 3 , .Xr EVP_PKEY_derive 3 , .Xr EVP_PKEY_encrypt 3 , .Xr EVP_PKEY_meth_set_keygen 3 , .Xr EVP_PKEY_sign 3 , .Xr EVP_PKEY_verify 3 , .Xr EVP_PKEY_verify_recover 3 , .Xr X25519 3 .Sh HISTORY These functions first appeared in OpenSSL 1.0.0 and have been available since .Ox 4.9 .