.\"	$OpenBSD: DH_new.3,v 1.11 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>.
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.Dd $Mdocdate: June 10 2019 $
.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 crypto 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 EVP_PKEY_CTX_set_dh_paramgen_prime_len 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 .