Multicast communication enables the distribution of digital content from a single source to a large audience via a public channel such as the Internet. Broadcasting has applications in sensor networks, pay-TV, software updates and military defence systems to name a few. As these applications will distribute private or sensitive information, multicast protocols must provide data origin authentication.

Broadcast channels have limited bandwidth and may be under the influence of opponents deleting, inserting and reordering data packets. In such a context, the security of authentication protocols relies on two aspects: the opponents' computational powers and the network properties.

In this presentation, we will introduce provable secure protocols providing non-repudiation of the origin of a data stream over an unsecured communication channel. We will emphasize that our constructions provide practical solutions to the stream authentication problem, i.e. the requirements of provable security are compatible with the settings of broadcasting.