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Optimizing Information Set Decoding Algorithms to Attack Cyclosymetric MDPC Codes



Ray A. Perlner


The most important drawback to code-based cryptography has historically been its large key sizes. Recently, several promising approaches have been proposed to reduce keysizes. In particular, significant keysize reduction has been achieved by using structured, but non-algebraic codes, such as quasi-cyclic or quasi-dyadic Moderate Density Parity Check (MDPC) codes. Biasi et al. propose further reducing the keysizes of code-based schemes using cyclosymmetric (CS) codes. Biasi et al analyze the complexity of attacking their scheme against standard information-set-decoding attacks. However, the research presented here shows that information set decoding algorithms can be modified, by choosing the columns of the information set in a way that takes advantage of the added symmetry. The result is an attack that significantly reduces the security of the proposed CS-MDPC schemes to the point that they no longer offer an advantage in keysize over QC-MDPC schemes of the same security level.
Proceedings Title
Post-Quantum Cryptography (Lecture Notes in Computer Science)
Conference Dates
October 1-3, 2014
Conference Location
Conference Title
6th International Conference on Post-Quantum Cryptography (PQCrypto 2014)


information set decoding, code-based cryptography, moderate density parity check (MDPC) codes, cyclosymmetric


Perlner, R. (2014), Optimizing Information Set Decoding Algorithms to Attack Cyclosymetric MDPC Codes, Post-Quantum Cryptography (Lecture Notes in Computer Science), Waterloo, -1, [online], (Accessed June 16, 2024)


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Created October 3, 2014, Updated November 10, 2018