R&D of New Cryptographic Technologies with Long-Term Usability

量子计算的发展对现有公钥密码体制的安全性构成了严重威胁。能够抵御量子攻击并可以在传统计算机上运行的密码系统是可取的，被称为后量子密码系统。另一方面，公共云存储服务提供了几个好处，包括可用性（能够从任何地方访问数据）和可靠性，成本相对较低。一个可采用的云存储服务应该旨在通过提供私有云的安全性和公共云的功能性来实现两个世界的最佳效果。我们调查了具有长期可用性的加密技术，涉及以下两个问题：后量子密码学（基于格的密码学和非交换密码学）和用于云安全的实用密码学（代理再加密、阈值加密、秘密共享方案和使用同态加密的位置认证等）。

The development of quantum computation casts serious threats to the security of most existing public-key cryptosystems. Cryptosystems that are secure against quantum attacks and can be run on traditional computers are desirable and known as post-quantum cryptosystems. On the other hand, public cloud storage service provides several benefits, including availability (being able to access data from anywhere) and reliability, at a relatively low cost. An adoptable cloud storage service should aim to achieve the best of both worlds by providing the security of a private cloud and the functionality of a public cloud.We investigated cryptographic technologies with long-term usability on the following two issues: Post-Quantum Cryptography (Lattice-based cryptography and non-commutative cryptography) and Practical Cryptography for Cloud Security (proxy re-encryption, threshold encryption, secret sharing scheme, and position authentication using homomorphic encryption, etc.).