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.\" $OpenBSD: DSA_dup_DH.3,v 1.8 2019/06/10 14:58:48 schwarze Exp $
.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000, 2002 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_DUP_DH 3
.Os
.Sh NAME
.Nm DSA_dup_DH
.Nd create a DH structure out of DSA structure
.Sh SYNOPSIS
.In openssl/dsa.h
.Ft DH *
.Fo DSA_dup_DH
.Fa "const DSA *r"
.Fc
.Sh DESCRIPTION
.Fn DSA_dup_DH
duplicates
.Vt DSA
parameters/keys as
.Vt DH
parameters/keys.
.Fa r->q
is lost during that conversion, but the resulting
.Vt DH
parameters contain its length.
.Sh RETURN VALUES
.Fn DSA_dup_DH
returns the new
.Vt DH
structure or
.Dv NULL
on error.
The error codes can be obtained by
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr DH_new 3 ,
.Xr DSA_get0_pqg 3 ,
.Xr DSA_new 3
.Sh HISTORY
.Fn DSA_dup_DH
first appeared in OpenSSL 0.9.4 and has been available since
.Ox 2.6 .
.Sh CAVEATS
Be careful to avoid small subgroup attacks when using this.
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