A CCA2-Secure Multi-Decrypter Encryption Scheme Without Random Oracles

In a multi-decrypter encryption (MDE) scheme, a message encrypted under the public keys of multiple receivers can be recovered only when all the receivers designated by the sender are available (e.g. in a national security setting where a Top Secret document can only be decrypted and recovered when all the designated keyholders present the respective keys). Despite its effectiveness (i.e. without heavy computational overheads) in ensuring a message can only be read when all the designated parties are available, this is an under-researched topic (there are only two published MDE schemes in the literature, to the best of our knowledge). In this paper, we propose an efficient MDE scheme and prove its CCA2 security in the standard model under the decisional bilinear Diffie-Hellman assumption.