H.235 covers security and encryption for H.323 and other H.245 based terminals.

The standard addresses authentication by means of several algorithms, including Diffie-Hellman methods, and privacy. Privacy allows for encryption, also of the media streams.

The standardization board agreed on H.235, Annex D to be the minimum requirement of an H.235 conform implementation. The Annex D a.k.a Baseline Security Profile defines Authentication and Integrity.

An Annex D aware Gatekeeper can thereby assure that only trusted H.323 endpoints are granted access to the Gatekeeper's services.