Paper 2008/103

Identity-Based Proxy Re-encryption Schemes with Multiuse, Unidirection, and CCA Security

Jun Shao, Dongsheng Xing, and Zhenfu Cao

Abstract

A proxy re-encryption (PRE) scheme allows a proxy to transform a ciphertext under Alice's public key into a ciphertext under Bob's public key on the same message. In 2006, Green and Ateniese extended the above notion to identity-based proxy re-encryption (IB-PRE), and proposed two open problems \cite{GA06}: building 1. IB-PRE schemes which are CCA-secure in the standard model; 2. multi-use CCA-secure IB-PRE schemes. Chu and Tzeng proposed two identity-based proxy re-encryption schemes afterwards in \cite{CT07}, aiming at solving the two open problems. However, in this paper, we show that they don't solve these two open problems by revealing a security flaw in their solution. Furthermore, we propose an improvement which is a solution to the open problems.