How to securely broadcast a secret

The conference key distribution problem over a broadcast channel, i.e. distribution of a key to a set of recipients by a central authority, can be solved by true broadcasting using threshold schemes. This paper gives a security analysis of this approach. After describing succesful attacks on two special implementations of true broadcasting schemes, a slightly different scheme is shown to be provably secure under some well-known cryptographic assumptions. As an application of the threshold scheme approach, a subliminal channel free scheme is given which can be used e.g, in Pay-TV systems.