A Hybrid Encryption Scheme with Key-cloning Protection: User / Terminal Double Authentication via Attributes and Fingerprints

Internet service has enabled digital contents to be shared faster and easier, but on the other side it raised an issue of illegal copy of the digital contents. Public key encryption schemes solve this issue partially. However, there is still a weak point that the secret key is not completely protected; that is, public key encryption schemes suffer from illegal copy of secret keys (the key-cloning problem). In this paper, first, we discuss the usability of terminal fingerprints for key-cloning protection. Next, we propose a hybrid encryption scheme using terminal fingerprints to protect the secret keys from the key-cloning. Based on an assumption that the terminal fingerprint is unchangeable and unextractable even by the user of the terminal, our hybrid encryption scheme can be effectively used as a method of the key-cloning protection. Then, we instantiate our hybrid encryption scheme as a combination of the attribute-based encryption scheme and the RSA encryption scheme; the attribute-based encryption scheme functions as a mechanism for authentication of user’s attributes, and the RSA encryption scheme functions as a mechanism for authentication of a terminal device. Terminal fingerprint that is a feature of the device is used to generate a secret key of the RSA encryption.