Addressing leakage of re-encryption key in proxy re-encryption using trusted computing

Abstract

Proxy re-encryption is a cryptographic primitive enabling a proxy holding a re-encryption key to convert a ciphertext originally intended for Alice (delegator) into an encryption of the same message for Bob (delegatee). Proxy re-encryption is a useful tool, having many applications. However, we observe that the issue of re-encryption key leakage, where the delegatee acquires the re-encryption key from the proxy, has been neglected by virtually all of the existing work. Possession of the re-encryption key allows the delegatee to decrypt the delegator's ciphertexts by himself, without necessarily turning to the proxy for conversion, which may contradict the delegator's interest. In this work, we present a method to address this issue using trusted computing technology. Our proposal represents yet another application of trusted computing. © 2011 Springer-Verlag.