uSMIL: Towards secure unbreakable semantics in multimedia web services

摘要

Web-based services are becoming omnipresent due to the multifold increase in user adaptability and are now also enabling state of the art services such as audiovisual surveillance, monitoring and recording of unfolding real world scenes. In such applications the chronological order of events and integrity of the audio/video components is very crucial. Further, most of the web services are driven by a policy that governs the preparation and presentation of the sensitive data. Leaving room to alter the chronology of such real-world recordings would facilitate the ability to fabricate audiovisual evidence, thereby seriously eroding emerging public trust on these up and coming services. One way of avoiding this problem is to be able to specify which chronology building composition operators - otherwise known as multimedia synchronization constructs - such as before, after, simultaneously etc., have more rigid failure semantics. The existing W3C standard for multimedia services, synchronized multimedia integration language (SMIL) does not provide them. In order to address this deficiency, we propose uSMIL - an extension of SMIL that allows the creation of non-decomposable stream bundles with an all or nothing playout semantics. These semantics enable the web-service to be secure while being compliant with any governing policy. In this paper we present formal operational semantics for uSMIL and show some of its algebraic properties with pertinent examples.