The purpose of this Recommendation is to provide recommendations of security procedures for using direct-routed call signalling in conjunction with H.235.1 and H.235.3 security profiles. This security profile is offered as an option and may complement the security profiles in ITU-T Recs H.235.1 and H.235.3. It also provides implementation details for clause 8.4/H.235.0 using symmetric key management techniques. In earlier versions of the H.235 subseries, this profile was contained in Annex I/H.235. Appendices IV, V, VI to H.235.0 show the complete clause, figure, and table mapping between H.235 versions 3 and 4.