[#DH_compute_key_padded]
= DH_compute_key_padded
:mrdocs:

Derive the DH shared secret with NIST SP 800‐56A leading‐zero padding (deprecated).

== Synopsis

Declared in `<openssl/dh.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[deprecated]]
int
DH_compute_key_padded(
    unsigned char* key,
    xref:BIGNUM.adoc[BIGNUM] const* pub_key,
    xref:DH.adoc[DH]* dh);
----

[WARNING]
====
https://en.cppreference.com/cpp/language/attributes/deprecated[Deprecated^]. Use of this entity is allowed but discouraged.
====
== Description

Like DH_compute_key() but always writes DH_size(`dh)` bytes, retaining leading zeros (constant‐time w.r.t. the secret length). Prefer EVP_PKEY_derive for new code.

== Return Value

DH_size(`dh)` on success, or ‐1 on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *key*
| Output buffer of at least DH_size(`dh)` bytes.
| *pub_key*
| Peer public value.
| *dh*
| DH object holding the private key and domain parameters.
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#