Fully homomorphic encryption (FHE) is an emerging public key encryption paradigm, which enables a third party to execute operations on ciphertexts without knowing the decryption key. It can serve as a powerful cryptographic tool for data privacy protection in cloud computing environment, and has significant applications. However, in a complex network environment, a message may be received by multiple receivers. It has not been well solved by the traditional FHE schemes as how to share a computable ciphertext with an arbitrarily chosen set of receivers. Inspired by identity-based broadcast encryption, we introduce a novel cryptography primitive called identity-based broadcast fully homomorphic encryption (IBBFHE), and present a concrete scheme based on LWE assumption to solve the problem mentioned above. The data encrypted under IBBFHE schemes can still be homomorphic computed by third parties who do not have decryption abilities, and it can only be decrypted by the authorized receivers in a specific group. Thus, data secure sharing can be made possible in cloud computing environment. The IND-smCIS-CPA security of the proposed scheme under LWE assumption is proved. Furthermore, LWE problem is believed to be unsolvable by quantum computers, thus the proposed scheme also possesses this property.
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2018, Vol. 5 
