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.\" $OpenBSD: DSA_generate_parameters.3,v 1.12 2019/06/10 14:58:48 schwarze Exp $
.\" OpenSSL 9b86974e Aug 7 22:14:47 2015 -0400
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>,
.\" Bodo Moeller <bodo@openssl.org>, and Matt Caswell <matt@openssl.org>.
.\" Copyright (c) 2000, 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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.\"
.Dd $Mdocdate: June 10 2019 $
.Dt DSA_GENERATE_PARAMETERS 3
.Os
.Sh NAME
.Nm DSA_generate_parameters_ex ,
.Nm DSA_generate_parameters
.Nd generate DSA parameters
.Sh SYNOPSIS
.In openssl/dsa.h
.Ft int
.Fo DSA_generate_parameters_ex
.Fa "DSA *dsa"
.Fa "int bits"
.Fa "const unsigned char *seed"
.Fa "int seed_len"
.Fa "int *counter_ret"
.Fa "unsigned long *h_ret"
.Fa "BN_GENCB *cb"
.Fc
.Pp
Deprecated:
.Pp
.Ft DSA *
.Fo DSA_generate_parameters
.Fa "int bits"
.Fa "unsigned char *seed"
.Fa "int seed_len"
.Fa "int *counter_ret"
.Fa "unsigned long *h_ret"
.Fa "void (*callback)(int, int, void *)"
.Fa "void *cb_arg"
.Fc
.Sh DESCRIPTION
.Fn DSA_generate_parameters_ex
generates primes p and q and a generator g for use in the DSA and stores
the result in
.Fa dsa .
.Pp
.Fa bits
is the length of the prime to be generated; the DSS allows a maximum of
1024 bits.
.Pp
If
.Fa seed
is
.Dv NULL
or
.Fa seed_len
< 20, the primes will be generated at random.
Otherwise, the seed is used to generate them.
If the given seed does not yield a prime q, a new random seed is chosen
and placed at
.Fa seed .
.Pp
.Fn DSA_generate_parameters_ex
places the iteration count in
.Pf * Fa counter_ret
and a counter used for finding a generator in
.Pf * Fa h_ret ,
unless these are
.Dv NULL .
.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 shown below.
For information on the
.Vt BN_GENCB
structure, refer to
.Xr BN_GENCB_call 3 .
.Bl -bullet
.It
When a candidate for q is generated,
.Fn BN_GENCB_call cb 0 m++
is called
.Pf ( Fa m
is 0 for the first candidate).
.It
When a candidate for q has passed a test by trial division,
.Fn BN_GENCB_call cb 1 -1
is called.
While a candidate for q is tested by Miller-Rabin primality tests,
.Fn BN_GENCB_call cb 1 i
is called in the outer loop (once for each witness that confirms that
the candidate may be prime);
.Fa i
is the loop counter (starting at 0).
.It
When a prime q has been found,
.Fn BN_GENCB_call cb 2 0
and
.Fn BN_GENCB_call cb 3 0
are called.
.It
Before a candidate for p (other than the first) is generated and tested,
.Fn BN_GENCB_call cb 0 counter
is called.
.It
When a candidate for p has passed the test by trial division,
.Fn BN_GENCB_call cb 1 -1
is called.
While it is tested by the Miller-Rabin primality test,
.Fn BN_GENCB_call cb 1 i
is called in the outer loop (once for each witness that confirms that
the candidate may be prime).
.Fa i
is the loop counter (starting at 0).
.It
When p has been found,
.Fn BN_GENCB_call cb 2 1
is called.
.It
When the generator has been found,
.Fn BN_GENCB_call cb 3 1
is called.
.El
.Pp
.Fn DSA_generate_parameters
(deprecated) works in much the same way as for
.Fn DSA_generate_parameters_ex ,
except that no
.Fa dsa
parameter is passed and instead a newly allocated
.Vt DSA
structure is returned.
Additionally "old style" callbacks are used instead of the newer
.Vt BN_GENCB
based approach.
Refer to
.Xr BN_generate_prime 3
for further information.
.Sh RETURN VALUES
.Fn DSA_generate_parameters_ex
returns a 1 on success, or 0 otherwise.
.Pp
.Fn DSA_generate_parameters
returns a pointer to the
.Vt DSA
structure, or
.Dv NULL
if the parameter generation fails.
.Pp
The error codes can be obtained by
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr BN_generate_prime 3 ,
.Xr DSA_get0_pqg 3 ,
.Xr DSA_new 3
.Sh HISTORY
.Fn DSA_generate_parameters
first appeared in SSLeay 0.8.0 and had its
.Fa cb_arg
argument added in SSLeay 0.9.0.
It has been available since
.Ox 2.4 .
.Pp
In versions up to OpenSSL 0.9.4,
.Fn callback 1 ...\&
was called in the inner loop of the Miller-Rabin test whenever it
reached the squaring step (the parameters to
.Fn callback
did not reveal how many witnesses had been tested); since OpenSSL 0.9.5,
.Fn callback 1 ...\&
is called as in
.Xr BN_is_prime 3 ,
i.e. once for each witness.
.Pp
.Fn DSA_generate_parameters_ex
first appeared in OpenSSL 0.9.8 and has been available since
.Ox 4.5 .
.Sh BUGS
Seed lengths > 20 are not supported.
|
