Paper 2018/1136 Original: eprint.iacr.org/2018/1136 ↗

A Provably-Secure Unidirectional Proxy Re-Encryption Scheme Without Pairing in the Random Oracle Model

Abstract

Proxy re-encryption (PRE) enables delegation of decryption rights by entrusting a proxy server with special information, that allows it to transform a ciphertext under one public key into a ciphertext of the same message under a different public key. It is important to note that, the proxy which performs the re-encryption learns nothing about the message encrypted under either public keys. Due to its transformation property, proxy re-encryption schemes have practical applications in distributed storage, encrypted email forwarding, Digital Rights Management (DRM) and cloud storage. From its introduction, several proxy re-encryption schemes have been proposed in the literature, and a majority of them have been realized using bilinear pairing. In Africacrypt 2010, the first PKI-based collusion resistant CCA secure PRE scheme without pairing was proposed in the random oracle model. In this paper, we point out an important weakness in the scheme. We also present the first collusion-resistant pairing-free unidirectional proxy re-encryption scheme which meets CCA security under a variant of the computational Diffie-Hellman hardness assumption in the random oracle model.