A New Insight—Proxy Re-encryption Under LWE with Strong Anti-collusion

Abstract

Proxy re-encryption is a special type of public key encryption that allows an intermediate proxy to transform a ciphertext from one public key to another without learning any information about the original message. Therefore, it can be regarded as a consignation of decryption right. In this paper, we put forward two novel definitions of anti-collusion called strong anti-collusion and weak anti-collusion, and propose an improved strong anti-collusion lattice based proxy re-encryption scheme. Moreover, our scheme based on the hardness of standard Learning With Error (LWE) problem is the CPA secure in the standard model, which can be reduced to the worst-case lattice hard problems. In addition, we give a detailed analysis of key privacy and proof of security.