Proxy Re-encryption Scheme from IBE to CBE

In 1998, Blaze, Bleumer, and Strauss proposed a kind of cryptographic primitive called proxy re-encryption [3]. In proxy re-encryption, a proxy can transform a ciphertext computed under Alice's public key into one that can be opened under Bob's decryption key. They predicated that proxy reencryption and re-signature will play an important role in our life. In 2007, Matsuo proposed the concept of four types of reencryption schemes: CBE to IBE(type 1), IBE to IBE(type 2), IBE to CBE (type 3), CBE to CBE (type 4) [17]. Now CBE to IBE and IBE to IBE proxy re-encryption schemes are being standardized by IEEEP1363.3 working group [18]. In this paper, based on [17] we propose a proxy re-encryption scheme from IBE to CBE. To the best of our knowledge, this is the first type 3 scheme. We give the security model for proxy re-encryption scheme from IBE to CBE and prove our scheme's security in this model without random oracle.