Date Added: Apr 2011
This paper proposes a new cryptographic primitive, named Identity-Based Conditional Proxy Re-Encryption (IBCPRE). In this primitive, a proxy with some information (a.k.a. reencryption key) is allowed to transform a subset of ciphertexts under an identity to other ciphertexts under another identity. Due to the specific transformation, IBCPRE is very useful in encrypted email forwarding. Furthermore, the authors propose a concrete IBCPRE scheme based on Boneh-Franklin identity-based encryption. The proposed IBCPRE scheme is secure against the chosen ciphertext and identity attack in the random oracle model.