In this paper, we attack the recent NIST submission Giophantus, a public key encryption scheme. We find that the complicated structure of Giophantus's ciphertexts leaks information via a correspondence from a low dimensional lattice. This allows us to distinguish encrypted data from random data by the LLL algorithm. This is a more efficient attack than previous proposed attacks.
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K. Akiyama, Y. Goto, S. Okumura, T. Takagi, K. Nuida, G. Hanaoka, H. Shimizu and Y. Ikematsu, A public-key encryption scheme based on non-linear indeterminate equations (giophantus), Cryptology ePrint Archive, Report 2017/1241, (2017). Available from: https://eprint.iacr.org/2017/1241.
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