SRTP Store-and-Forward Use Cases and Requirements

The Secure Real-time Transport Protocol (SRTP) was designed to allow simple and efficient protection of RTP. To provide this, encryption and authentication of media and control signaling are tightly coupled to the RTP session, and to the information in the RTP header. Hence, in general it is not possible to perform store and forward of protected media. This document gives, based on a use case analysis, requirements that SRTP and new SRTP transforms need to satisfy in order to allow secure store-and-forward operation. A first proposal on how to introduce the needed new functionality and transforms in SRTP is also presented.