Constant-size CCA-secure multi-hop unidirectional proxy re-encryption from indistinguishability obfuscation

In ACM CCS 2007, Canetti and Hohenberger left an open problem of how to construct a multi-hop unidirectional proxy re-encryption scheme secure against chosen-ciphertext attacks (CCA). To resolve this problem, we utilize the recent advances in indistinguishability obfuscation, overcome several obstacles and propose a multi-hop unidirectional proxy re-encryption scheme. The proposed scheme is proved to be CCA-secure in the standard model (i.e., without using the random oracle heuristic), and its ciphertext remains constant-size regardless of how many times it has been transformed. It is worth noting that, our techniques proposed in this paper can also be used to construct an identity-based multi-hop unidirectional PRE scheme with constant-size ciphertexts and CCA-security in the standard model. (C) 2020 Elsevier B.V. All rights reserved.