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学术报告:Cryptanalysis of Compact-LWE Submitted to NIST PQC Project

2018-04-24        撰稿人: 张道德


时间:2018年4月26日 周四 下午2:00


内容提要:Recently, Liu, Li, Kim and Nepal submitted a new public-key encryption scheme Compact-LWE to NIST as a candidate of the standard of post-quantum cryptography. Compact-LWE features its structure similar to LWE, but requiring somewhat big errors. In terms of the security of Compact-LWE, the authors claimed that ``even if the hard problems in lattice, such as CVP and SIS, can be efficiently solved, the secret values or private key in Compact-LWE still cannot be efficiently recovered. This allows Compact-LWE to choose very small dimension parameters, such as n = 8 in our experiment". In this paper, we show the claim is not true by proposing a ciphertext-only attack against Compact-LWE. More precisely, we can decrypt any ciphertext without knowing the private keys with the help of CVP algorithm. Since the dimension of the underlying lattice of Compact-LWE is quite small (128) for the authors' parameter choice, approximate CVP can be efficiently solved using lattice basis reduction algorithm, which concludes that Compact-LWE with recommended parameters is not secure.



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