Attribute-based broadcast encryption scheme for lightweight devices

Lightweight devices, such as a smartcard associated with a top-box decoder in pay-TV or a SIM card coupled with a powerful (but not totally trusted) smartphone, play an important role in modern applications. The essential requirements for a cryptographic scheme to be truly implemented in lightweight devices are that it should have compact secret key size and support fast decryption. Attribute-based broadcast encryption (ABBE) combines the functionalities of both broadcast encryption and attribute-based encryption in an efficient way, ABBE is therefore a promising cryptographic scheme to be used in practical applications such as mobile pay-TV, satellite transmission, or Internet of Things. Designing an ABBE scheme which can be truly implemented in lightweight devices is still an open question. In this study, the authors solve it by proposing an efficient constant-size private key ciphertext-policy ABBE scheme for disjunctive normal form supporting fast decryption and achieving standard security levels of an ABBE scheme. They concretely show that the authors' scheme can be truly implemented in a prototype for a smartphone-based cloud storage use case. In particular, they show how to alleviate some parts of their scheme so as to obtain a very practical system, and they give some concrete benchmarks.