Security of Scalable Multimedia Streams

The demand for multimedia services has been rapidly increasing over the past few years. More and more users rely on multimedia services for many aspects of their daily lives, including work, education, and entertainment. This makes the security of delivering multimedia content of great importance. Therefore, we focus on providing source authentication and data integrity services for media stream, i.e., ensuring that streams being played by receivers are original and have not been tampered with by malicious attackers. Our especial focus is on scalable video streams, which are becoming very popular with respect to recent advances in scalable coding and the increasing heterogeneity among receiver devices.

A number of major challenges rise when considering authentication of scalable video streams. First, digital signature operations, which are the foundation of authentication processes, are too computationally expensive to be performed frequently in real-time, especially by limited-capability devices such as cell phones and PDAs. Second, flexibility of scalable videos needs to be supported by the authentication scheme. A scalable video is encoded and signed once, and there can be many valid substreams extractable from one bitstream, each of which needs to be authenticated. Third, packet losses frequently take place in transmission networks, especially in wireless channels. Counteracting the impact of loss in video transmission scenarios is approached by several techniques such as Forward Error Correction (FEC), interleaved packetization, etc. This impact in case of "authenticated" video gets more highlighted. Due to the dependency that the authentication mechanism may impose on video packets, it may amplify the loss ratio of the network; a video packet and its authentication information must both be successfully received, or the video packet is unusable even though it is not lost. The authentication scheme should have zero or negligible such effect. Fourth, some additional information needs to be attached to the stream by the authentication mechanism in order for receivers to be able to verify the stream. The amount of this information needs to be carefully controlled, since bandwidth is a limited resource and should not be non-negligibly occupied by the authentication information.

We are investigating the above four challenges and several other subtle issues for authentication of scalable video streams in a computationally efficient manner, with low delay and communication overhead and high resilience to packet losses. We also performed systematic tamperings with scalable videos with very limited manipulation possibilities in order to highlight the importance of our approaches. Our main focus is on recent scalable video structures, such as the state-of-the-art H.264/SVC standard, which follow a more complex structure compared to traditional simple scalable videos, and can flexibly support different types of scalability by using various coding tools.

People

• Mohamed Hefeeda (Assistant Professor)

• Kianoosh Mokhtarian (MSc Student)

Publications

• M. Hefeeda and K. Mokhtarian, “Authentication Schemes for Multimedia Streams: Quantitative Analysis and Comparison,” To appear in ACM Transactions on Multimedia Computing, Communications and Applications.

• M. Hefeeda and K. Mokhtarian, “Security of Scalable Multimedia Streams,” Handbook on Security and Networks, World Scientific Publishing Co., To appear in summer 2009.

Software

• svcAuth: An Authentication Scheme for Securing the Delivery of H.264/SVC Video Streams