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**1 - 2**of**2**### Secure Real-Time Streaming Protocol (RTSP) for Hierarchical Proxy Caching

, 2006

"... 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 in ..."

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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.

### Scheduling Split Intervals

, 2005

"... We consider the problem of scheduling jobs that are given as groups of non-intersecting segments on the real line. Each job Jj is associated with an interval, Ij, which consists of up to t segments, for some t> = 1, and a weight (profit), wj; two jobs are in conflict if their intervals intersec ..."

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We consider the problem of scheduling jobs that are given as groups of non-intersecting segments on the real line. Each job Jj is associated with an interval, Ij, which consists of up to t segments, for some t> = 1, and a weight (profit), wj; two jobs are in conflict if their intervals intersect. Such jobs show up in a wide range of applications, including the transmission of continuous-media data, allocation of linear resources (e.g. bandwidth in linear processor arrays), and in computational biology/geometry. The objective is to schedule a subset of non-conflicting jobs of maximum total weight. Our problem can be formulated as the problem of finding a maximum weight independent set in a t-interval graph (the special case of t = 1 is an ordinary interval graph). We show that, for t> = 2, this problem is APX-hard, even for highly restricted instances. Our main result is a 2t-approximation algorithm for general instances. This is based on a novel fractional version of the Local Ratio technique. One implication of this result is the first constant factor approximation for non-overlapping alignment of genomic sequences. We also derive a bi-criteria polynomial time approximation scheme for a restricted subclass of t-interval graphs.