Ad hoc broadcast encryption

Numerous applications in ad hoc networks, peer-to-peer networks, and on-the-fly data sharing call for confidential broadcast without relying on a dealer. To cater for such applications, we propose a new primitive referred to as ad hoc broadcast encryption (AHBE), in which each user possesses a public key and, upon seeing the public keys of the users, a sender can securely broadcast to any subset of them, so that only the intended users can decrypt. We implement a concrete AHBE scheme proven secure under the decision Bilinear Diffie-Hellman Exponentiation (BDHE) assumption. The resulting scheme has sub-linear complexity, comparable to up-to-date broadcast systems which have also sub-linear complexity but require a fully trusted dealer.