Two Constructions of Multireceiver Encryption Supporting Constant Keys, Short Ciphertexts, and Identity Privacy

Multireceiver encryption enables a sender to encrypt a message and transmit the ciphertext to a set of authorized users while no one outside this set can decrypt the message, which is known as an efficient protocol to achieve a secure multicast data communication among multiple authorized users. In this work, we construct two identitybased multireceiver encryption schemes (one is based on composite order groups whose order is a product of three primes and the other is based on prime order of asymmetric bilinear groups where the isomorphisms between two groups are not efficiently computable) that support: (1)unbounded recipient in multireceiver set that does not pre-establish the maximum number of multireceiver users in advance in the setup algorithm; (2)identity privacy that no one outside the multireceiver set can derive the identities of multireceiver users, and (3)higher computing and communicating performance, i.e., short ciphertexts, fixlength public parameters and constant keys. The security analysis, including semantic security and identity privacy, are presented in selective security model under the mathematical assumptions of (bilinear) subgroup decisional problems in composite order model and decisional BDH problems in prime order of asymmetric bilinear groups in the standard model.