On the Role of PKG for Proxy Re-encryption in Identity Based Setting

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. In 2007, Matsuo proposed the concept of four types of proxy re-encryption schemes: CBE(Certificate Based Public Key Encryption) to IBE(Identity Based Encryption)(type 1), IBE to IBE(type 2), IBE to CBE (type 3), CBE to CBE (type 4)[29]. Now CBE to IBE and IBE to IBE proxy re-encryption schemes are being standardized by IEEEP1363.3 working group[31]. In this paper, based on [29] we pay attention to the role of PKG for proxy re-encryption in identity based setting. We find that if we allow the PKG to use its master-key in the process of generating re-encryption key for proxy re-encryption in identity based setting, many open problems can be solved. Our main results are as following: We construct the first proxy re-encryption scheme from CBE to IBE which can resist malicious PKG attack, the first proxy re-encryption scheme from IBE to CBE, the second proxy re-encryption scheme based on a variant of BB1 IBE , the first proxy re-encryption scheme based on BB2 IBE, the first proxy re-encryption scheme based on SK IBE, we also prove their security in their corresponding security models.