.Dd $Mdocdate: November 2 2016 $
.Dt DH_SIZE 3
.Os
.Sh NAME
.Nm DH_size
.Nd get Diffie-Hellman prime size
.Sh SYNOPSIS
.In openssl/dh.h
.Ft int
.Fo DH_size
.Fa "DH *dh"
.Fc
.Sh DESCRIPTION
This function returns the Diffie-Hellman size in bytes.
It can be used to determine how much memory must be allocated for the
shared secret computed by
.Xr DH_compute_key 3 .
.Pp
.Fa dh->p
must not be
.Dv NULL .
.Sh RETURN VALUE
The size in bytes.
.Sh SEE ALSO
.Xr dh 3 ,
.Xr DH_generate_key 3
.Sh HISTORY
.Fn DH_size
is available in all versions of SSLeay and OpenSSL.