Related-key impossible differential cryptanalysis on Crypton and Crypton v1.0

Crypton is a 12-round block cipher proposed as an AES candidate and Crtpton v1.0 is the revised version. In this paper, we present two related-key impossible differential attacks to reduced-round Crypton and Crypton v1.0. By carefully choosing the relations of keys, constructing some 6-round related-key differential trials and using some observations on the cipher, we first break 9-round Crypton v1.0 and Crypton with 256 bit keys. This fact reflects some weaknesses of the key schedule algorithms of the two versions of Crypton when using 256 bits user keys.