Multi-Use Conditional Proxy Re-encryption

In this paper a scheme named multi-use conditional proxy re-encryption based on ECC is proposed first, which can be used in the following email service scenarios: Alice can delegate her decryption rights to Bob for an encrypted mails sent to her, which contains a specific word and satisfies the condition set on the proxy by Alice, and Bob also can delegate the right to others just like Alice through the proxy, as the condition set by him is satisfied, and so on if required. Furthermore, as an important part for fulfilling our main goal, a new method to generate the partial re-encryption keys is proposed, and the security of our scheme is proven secure against chosen cipher text attacks based on the random oracle model.