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不经意传输协议(oblivious transfer,OT)因其简易的密码功能广泛应用于安全多方计算。以往OT协议都是基于传统数论问题(例如,离散对数,大数分解问题)所构造的,随着量子计算技术的发展,基于传统困难问题的OT协议安全性受到极大的威胁。因此,人们转而考虑使用后量子密码技术替代以往OT协议所依赖的传统困难问题。目前,已有一些基于后量子密码体制的OT协议被提出。然而,大多数后量子密码构造只在假设传统敌手存在的环境下证明其方案安全性。在本文中,我们在量子敌手存在的环境下,证明一个基于格公钥密码的OT协议([PVW08])的安全性。首先我们使用量子平移定理([Unr10])证明该协议的安全性可以完全平移到量子环境中,此外,我们还使用其他两个专用于分析后量子密码原语的分析模型([HSS11],[Son14])从不同的角度对该协议进行安全性分析,从而保证我们给出的量子安全证明的正确性。我们的成果可以看作对后量子密码协议分析模型的一个实际应用实例。
The oblivious transfer (OT) is widely used in secure multi-party computing for its simple cryptographic functions. In the past, OT protocol was constructed based on the traditional number-theoretic problems (such as discrete logarithm, large number decomposition). With the development of quantum computing technology, OT protocol security based on traditional hard-won problems is greatly threatened. Therefore, people turn to consider the use of post-quantum cryptography instead of the traditional OT protocol rely on the traditional problems. At present, some OT protocols based on post-quantum cryptography have been proposed. However, most post-quantum cryptographic constructs prove their scheme security only assuming the presence of traditional adversaries. In this paper, we prove the security of an OT protocol based on a lattice public key cryptosystem ([PVW08]) in the presence of quantum adversaries. First, we prove that the security of the protocol can be completely transposed to the quantum environment by using the quantum shift theorem ([Unr10]). In addition, we use two other analysis models ([HSS11], [ Son14]) from a different perspective of the protocol for security analysis, so as to ensure the correctness of the quantum security certificate we give. Our results can be seen as a practical application of the post-quantum cryptographic protocol analysis model.