SCCR: a generic approach to simultaneously achieve CCA security and collusion‐resistance in proxy re‐encryption

Abstract

AbstractBy allowing a proxy to blindly perform meaningful transformations from one ciphertext to another, proxy re‐encryption (PRE) is an important cryptographic primitive in many applications, such as encrypted email forwarding and distributed file system. Due to its usefulness, various PRE schemes have been proposed; however, only one can simultaneously achieve chosen ciphertext security (CCA security) and collusion‐resistance. When such schemes are deployed, lack of CCA security will cause secret leaking, and lack of collusion‐resistance will cause non‐repudiation damage. In this paper, we propose a novel approach (denoted SCCR) to simultaneously achieve CCA security and collusion‐resistance in PRE, which faces daunting new challenges. We address these challenges by using CCA‐secure (2, 2) threshold cryptosystem to obtain public verifiability, and the method of key management in identity‐based encryption (IBE) to achieve collusion‐resistance. These two novel techniques have not been yet used in any previous PRE schemes. A unique characteristic of SCCR is that it is a generic construction which has more advantages than a concrete PRE scheme does. Copyright © 2009 John Wiley & Sons, Ltd.