Identity Based Proxy Re-encryption From BB1 IBE

Abstract

In 1998, Blaze, Bleumer, and Strauss proposed a kind of cryptographic primitive called proxy re-encryption. 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). In this paper, we find that if we allow the PKG to use its masterkey in the process of generating re-encryption key for proxy re-encryption in identity based setting, many open problems can be solved. We give the new security models for proxy reencryption in identity based setting, especially considering PKG’s involving in the re-encryption key generation process and PKG’s master-key’s security. We construct the new IND-ID-CPA and the first IND-ID-CCA2 secure proxy reencryption schemes based on BB1 IBE. We also prove their security by introducing some new techniques which maybe have independent interest. At last, we compare our new schemes with existing ones, the results show that our scheme can achieve high security levels and are very efficient for re-encryption and, which are very important for practical applications.