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.\" $OpenBSD: DH_new.3,v 1.8 2018/04/18 01:11:45 schwarze Exp $
.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000 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: April 18 2018 $
.Dt DH_NEW 3
.Os
.Sh NAME
.Nm DH_new ,
.Nm DH_up_ref ,
.Nm DH_free
.Nd allocate and free DH objects
.Sh SYNOPSIS
.In openssl/dh.h
.Ft DH*
.Fn DH_new void
.Ft int
.Fo DH_up_ref
.Fa "DH *dh"
.Fc
.Ft void
.Fo DH_free
.Fa "DH *dh"
.Fc
.Sh DESCRIPTION
The DH functions implement the Diffie-Hellman key agreement protocol.
.Pp
.Fn DH_new
allocates and initializes a
.Vt DH
structure, setting the reference count to 1.
It is equivalent to
.Xr DH_new_method 3
with a
.Dv NULL
argument.
.Pp
.Fn DH_up_ref
increments the reference count by 1.
.Pp
.Fn DH_free
decrements the reference count by 1.
If it reaches 0, it frees the
.Vt DH
structure and its components.
The values are erased before the memory is returned to the system.
If
.Fa dh
is a
.Dv NULL
pointer, no action occurs.
.Sh RETURN VALUES
If the allocation fails,
.Fn DH_new
returns
.Dv NULL
and sets an error code that can be obtained by
.Xr ERR_get_error 3 .
Otherwise it returns a pointer to the newly allocated structure.
.Pp
.Fn DH_up_ref
returns 1 for success or 0 for failure.
.Sh SEE ALSO
.Xr BN_new 3 ,
.Xr d2i_DHparams 3 ,
.Xr DH_generate_key 3 ,
.Xr DH_generate_parameters 3 ,
.Xr DH_get0_pqg 3 ,
.Xr DH_get_ex_new_index 3 ,
.Xr DH_set_method 3 ,
.Xr DH_size 3 ,
.Xr DHparams_print 3 ,
.Xr DSA_dup_DH 3 ,
.Xr ERR_get_error 3 ,
.Xr EVP_PKEY_set1_DH 3
.Sh HISTORY
.Fn DH_new
and
.Fn DH_free
first appeared in SSLeay 0.5.1 and have been available since
.Ox 2.4 .
.Pp
.Fn DH_up_ref
first appeared in OpenSSL 0.9.7 and has been available since
.Ox 3.2 .
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