“空管私有云”是基于民航空管的专用网络，它能够充分整合空管系统的各种信息资源。为了保障空管信息的安全，数据需要被加密，以密文的形式存储在空管私有云中。然而，对加密后的空管信息的检索和处理，也因此变得异常困难。为了在不解密的情况下，仅仅通过处理密文，就能够同态的处理任意明文。本项目将开展全同态加密算法的研究，解决目前的全同态加密效率不高（目前最高的效率仅仅为安全参数的3.5次方），安全强度不够（达不到理论上的IND-CCA1安全）的关键性问题。主要研究内容包括：（1）高效的somewhat同态方案；（2）高效的重加密算法；（3）能够自评估的解密电路；（4）IND-CPA安全联合“明文感知安全”的可证明安全技术。通过在这些内容上的探索和创新，设计出高效而安全的全同态加密算法（安全参数的2次方、IND-CCA1安全），并设计在空管私有云中，具有示范价值的全同态加密的应用方案。

Based on CAAC Air Traffic Management (ATM) private network, Private Clouds can effectively integrate a variety of information resources in ATM system. In order to protect the ATM information security, data need be encrypted and stored in “ATM Private Clouds” in the form of ciphertexts. However, the indexing and processing of the encrypted ATM information will become extremely difficult. We want to operate the arbitrary plaintext information homomorphically, just by operating ciphertexts, without decryption. So, the project will focus on the research of Fully Homomorphic Encryption (FHE) algorithms to solve their efficiency and security problems. To the best of our knowledge, today the best efficiency is only λ^3.5 where λ is security parameter and the best security cannot still reach IND-CCA1 which is the theoretically strongest for FHE. The research includes 4 parts: (1) the efficient somewhat homomorphic encryption scheme, (2) the efficient recryption algorithm, (3) the squashed decryption circuit, and (4) the provable security technology by combination of IND-CPA and Plaintext-Awareness security. By creative jobs, we will propose efficient and secure FHE algorithms where the efficiency will be λ^2 and the security will be IND-CCA1. Furthermore, we will also design some application schemes to demonstrate the practical value of our algorithms in “ATM Private Clouds”.