A secure unidirectional proxy re-encryption using identity and secret key exchange

Abstract

Proxy re-encryption, abbreviated as PRE, is a cryptosystem which allows the proxy to re-encrypt a cirphertext without accessing the underlying message. The re-encryption protocol should be key independent to avoid compromising the private keys of the sender and the recipient. PRE should also be secure from signature re-usability, where unreliable proxies store and re-use the signatures without the authorization of the signature bearer. This is achieved by ensuring that PRE algorithm is unidirectional, key independent and the signature is dynamic. The proposed approach uses identity and secret key to prevent plain text and collusion attacks while ensuring that the delegator approves every signature used on his behalf. The algorithm used to generate the private/public keys is different from that generating the secret key. The proposed approach is secure even in unreliable proxies.