Abstract. Multimedia community is moving from monolithic applications to more flexible and scalable integrated solutions. Stream authentication is more complex since a stream may consist of multiple sources and be transcoded by intermediate proxies. In this paper, we propose a multi-source stream authentication (mSSA) framework based on MPEG4 stream format. We describe the overall authentication architecture and elaborate the encoding, hashing, signing, amortizing and verifying methods used in the basic scheme. Further on, we utilize advanced cryptographic primitives-aggregate signature schemes, to reduce the signatures’ size and improve the performance. We illustrate the scheme and discuss the extensions. Our analysis shows that the scheme is secure and efficient.