Collusion-Resistant Identity-Based Proxy Re-Encryption Without Random Oracles

Abstract

In an identity-based proxy re-encryption scheme, a semi-trusted proxy can convert a ciphertext under Alice’s public identity into a ciphertext for Bob. The proxy does not know the secret key of Alice or Bob, and also does not know the plaintext during the conversion. In identity-based proxy re-encryption, the collusion of the proxy and a delegatee may result in the decryption of ciphertext for delegator. In this paper, we present a new scheme which can avoid the collusion of proxy and delegatee. Our scheme improves the scheme of Chu and Tzeng while inheriting all useful properties such as unidirectionality and non-interactivity. In our scheme, we get the security by using added secret parameter and change the secret key and re-encryption key. Our sheme is secure against ChosenCiphertext Attack (CCA) and collusion attack in the standard model.