Compacting Ciphertext in Multi-Channel Broadcast Encryption and Attribute-Based Encryption

Multi-channel broadcast encryption (MCBE) and Attribute-based encryption (ABE) are important primitives used in a broad range of concrete application scenarios such as Pay-TV, e-Health, Cloud Storage, Blockchain and so on. The former allows a sender to efficiently send different messages to arbitrarily chosen sets of users (target sets) at the same time, while the latter supports more sophisticated access control by allowing both the encryption and decryption phases to be based on the user's attributes. Recently, Canard el al. at Theoretical Computer Science'18 proposed a new technique for compacting header size in both MCBE and ABE. However, their technique leads to schemes in secret-key setting which has limited applications in practice. In this paper, we propose a new technique also for compacting header size in both MCBE and ABE, but our technique leads to schemes in public key setting which therefore can overcome the weakness mentioned above of the Canard el al.'s technique. We finally implement our MCBE and ABE schemes to give some concrete benchmarks.