Known plaintext cryptanalysis of tree-structured block ciphers

The cryptanalysis of a class of block ciphers referred to as substitution-permutation networks (SPNs) is examined. Specifically, a novel attack applicable to tree-structured SPNs is presented. Since it uses a known plaintext approach, the attack is preferable to previously outlined chosen plaintext attacks. It is also shown that the attack is applicable to networks which are simple extensions of tree-structured SPNs