Doubly Encrypted Identity-Based Encryption for File Transfer Service

摘要

File transfer service demands that what users have to do is as little as possible and that no one can see the contents of a file except for a sender and a receiver of the file. In identity-based cryptography (IBC), one can use receiver's identity (ID) as a public key. There is no need to maintain public key certificates and to communicate preliminarily to get public keys. However, in common identity-based encryption (IBE), the decryption right is concentrated on the Private Key Generator (PKG) which generates every user's private key. Therefore, the PKG is asked for complete trust which is difficult to find in many realistic scenarios. In this paper, we propose an encryption scheme which encrypts a message doubly. By using our scheme, the decryption right is distributed to three servers, and the only receiver can decrypt ciphertext.