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.\" $OpenBSD: RSA_generate_key.3,v 1.13 2019/06/10 14:58:48 schwarze Exp $
.\" OpenSSL RSA_generate_key.pod bb6c5e7f Feb 5 10:29:22 2017 -0500
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000, 2002, 2013 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,
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\"
.Dd $Mdocdate: June 10 2019 $
.Dt RSA_GENERATE_KEY 3
.Os
.Sh NAME
.Nm RSA_generate_key_ex ,
.Nm RSA_generate_key
.Nd generate RSA key pair
.Sh SYNOPSIS
.In openssl/rsa.h
.Ft int
.Fo RSA_generate_key_ex
.Fa "RSA *rsa"
.Fa "int bits"
.Fa "BIGNUM *e"
.Fa "BN_GENCB *cb"
.Fc
.Pp
Deprecated:
.Pp
.Ft RSA *
.Fo RSA_generate_key
.Fa "int num"
.Fa "unsigned long e"
.Fa "void (*callback)(int, int, void *)"
.Fa "void *cb_arg"
.Fc
.Sh DESCRIPTION
.Fn RSA_generate_key_ex
generates a key pair and stores it in
.Fa rsa .
.Pp
The modulus size will be of length
.Fa bits ,
and the public exponent will be
.Fa e .
Key sizes with
.Fa num
< 1024 should be considered insecure.
The exponent is an odd number, typically 3, 17 or 65537.
.Pp
A callback function may be used to provide feedback about the progress
of the key generation.
If
.Fa cb
is not
.Dv NULL ,
it will be called as follows using the
.Xr BN_GENCB_call 3
function:
.Bl -bullet
.It
While a random prime number is generated, it is called as described in
.Xr BN_generate_prime 3 .
.It
When the
.Fa n Ns -th
randomly generated prime is rejected as not suitable for
the key,
.Fn BN_GENCB_call cb 2 n
is called.
.It
When a random p has been found with p-1 relatively prime to
.Fa e ,
it is called as
.Fn BN_GENCB_call cb 3 0 .
.El
.Pp
The process is then repeated for prime q with
.Fn BN_GENCB_call cb 3 1 .
.Pp
.Fn RSA_generate_key
is deprecated.
New applications should use
.Fn RSA_generate_key_ex
instead.
.Fn RSA_generate_key
works in the same way as
.Fn RSA_generate_key_ex
except it uses "old style" call backs.
See
.Xr BN_generate_prime 3
for further details.
.Sh RETURN VALUES
.Fn RSA_generate_key_ex
returns 1 on success or 0 on error.
.Fn RSA_generate_key
returns the key on success or
.Dv NULL
on error.
.Pp
The error codes can be obtained by
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr BN_generate_prime 3 ,
.Xr RSA_get0_key 3 ,
.Xr RSA_meth_set_keygen 3 ,
.Xr RSA_new 3
.Sh HISTORY
.Fn RSA_generate_key
appeared in SSLeay 0.4 or earlier and had its
.Fa cb_arg
argument added in SSLeay 0.9.0.
It has been available since
.Ox 2.4 .
.Pp
.Fn RSA_generate_key_ex
first appeared in OpenSSL 0.9.8 and has been available since
.Ox 4.5 .
.Sh BUGS
.Fn BN_GENCB_call cb 2 x
is used with two different meanings.
.Pp
.Fn RSA_generate_key
goes into an infinite loop for illegal input values.
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