Secure Real-Time Streaming Protocol (RTSP) for Hierarchical Proxy Caching

Abstract

Proxies are commonly used to cache objects, especially multimedia objects, so that clients can enjoy better quality-of-service (QoS) guarantees such as smaller startup latency and lower loss rate. But the use of multimedia proxies increases the risk that data are exposed to unauthorized access by intruders. In this paper, we propose an enhancement of the Internet IETF's Real-time Streaming Protocol (RTSP) which employs a notion of ”asymmetric reversible parametric sequence” (ARPS) to provide the following security properties: (i) data confidentiality during transmission, (ii) end-to-end data confidentiality, (iii) data confidentiality against proxy intruders, and (iv) data confidentiality against member collusion. We present the Secure Multimedia Library (SML) which is based on ARPS and then realize these security features on a production video streaming server: Apple's Darwin Streaming Server. Our framework guarantees the system resilience against attacks is provably strong given the standard computability assumptions. To reduce the computation demand on the receiving client, our scheme only requires the client to perform a ”single decryption operation” to recover the original data even though the data packets have been encrypted by multiple proxies along the delivery path. To tradeoff between degree of confidentiality and computational overhead, we also propose the use of a set of ”encryption configuration parameters” (ECP) to trade off proxy encryption throughput against the presentation quality of audio/video obtained by unauthorized parties. Our implementation prototype shows that one can simultaneously achieve high encryption throughput and extremely low audio/video quality (in terms of audio fidelity, and peak signal-to-noise ratio and visual quality of decoded video frames) for unauthorized access.