Fully Dynamic Multi Target Homomorphic Attribute-Based Encryption

We propose multi target homomorphic attribute-based encryption (MT-HABE) with fully dynamic homomorphic evaluation: it can take as input arbitrary additional ciphertexts during homomorphic computation. In the previousMT-HABE of Brakerski et al. (TCC 2016-B), the output of homomorphic computation, which is related to a policy set, cannot be computedwith a fresh ciphertext whose attribute does not satisfy any policy in the set. This is because the underlying multi-key fully homomorphic encryption (MKFHE) is single-hop: some keys are related to the output of homomorphic computation, which cannot be combined with ciphertexts encrypted under other keys. To implement fully dynamic homomorphic evaluations, we construct MT-HABE from the multi-hop MKFHE proposed by Peikert and Shiehian (TCC 2016-B). ∗Mitsubishi Electric. E-mail: [email protected] †Mitsubishi Electric. E-mail: [email protected]