Efficient authentication and signing of multicast streams over lossy channels

Multicast stream authentication and signing is an important and challenging problem. Applications include the continuous authentication of radio and TV Internet broadcasts, and authenticated data distribution by satellite. The main challenges are fourfold. First, authenticity must be guaranteed even when only the sender of the data is trusted. Second, the scheme needs to scale to potentially millions of receivers. Third, streamed media distribution can have high packet loss. Finally the system needs to be efficient to support fast packet rates. We propose two efficient schemes, TESLA and EMSS, for secure lossy multicast streams. TESLA (Timed Efficient Stream Loss-tolerant Authentication), offers sender authentication, strong loss robustness, high scalability and minimal overhead at the cost of loose initial time synchronization and slightly delayed authentication. EMSS (Efficient Multi-chained Stream Signature), provides nonrepudiation of origin, high loss resistance, and low overhead, at the cost of slightly delayed verification.