Technical Report CS0890

Title: Cryptanalysis of Ladder-DES
Authors: Eli Biham
Abstract: Feistel ciphers are very common and very important in the design and analysis of blockciphers, especially due to four reasons: (1)~Many (DES-like) ciphers are based on Feistel's construction. (2)~Luby and Rackoff proved the security of a four-round Feistel construction when the round functions are random. (3)~Recently several provably secure ciphers were suggested, which use other (assumed secure) ciphers as the round function. (4)~Other such ciphers use this construction as attempts to improve the security of other ciphers (e.g., to improve the security of DES).

In this paper we cryptanalyze Ladder-DES, a four-rounds Feistel cipher using DES in the round function, and show that its security is smaller than expected.

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