Recipient Anonymous Ciphertext-Policy Attribute-based Broadcast Encryption

The ciphertext-policy (CP) attribute-based broadcast encryption (CP-ABBE) is a more flexible broadcast encryption (BE), in which the broadcaster encrypts the data with an access policy and a receiver set. Only receivers in the valid set who satisfy the access policy will be able to decrypt the ciphertext. However, most existing CPABBE schemes only pay attention to plaintext privacy rather than access policy privacy and broadcast list privacy. It results in the fact that the adversary can determine the access policy or the broadcast set from ciphertexts and public parameters. However, in the real life, the access policy or the receiver set may be sensitive. To overcome this shortcoming, we propose a recipient anonymous CP-ABBE scheme, where it can protect the description of the access structures and broadcast sets associated with ciphertexts. The proposed scheme achieves full security based on the dual system encryption and constant size ciphertexts.