http://www.rfc-editor.org/rfc/rfc3853.txt
RFC 3853: S/MIME Advanced Encryption Standard (AES) Requirement for the Session Initiation Protocol (SIP), J. Peterson2004-07-01T23:00:00-00:00RFC 3261 currently specifies 3DES as the mandatory-to-implement ciphersuite for implementations of S/MIME in the Session Initiation Protocol (SIP). This document updates the normative guidance of RFC 3261 to require the Advanced Encryption Standard (AES) for S/MIME. [STANDARDS-TRACK]