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In page Data Encryption Standard:

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There are three attacks known that can break the full 16 rounds of DES with less complexity than a brute-force search: differential cryptanalysis (DC),[1] linear cryptanalysis (LC),[2] and Davies' attack.[3] However, the attacks are theoretical and are generally considered infeasible to mount in practice;[citation needed] these types of attack are sometimes termed certificational weaknesses.