Differential Cryptanalysis of the ICE Encryption Algorithm

ICE is a 64-bit block cipher presented at the Fast Software Encryption Workshop in January 1997. It introduced the concept of a keyed permutation to improve the resistance against differential and linear cryptanalysis. In this paper we will show however that we can use low Hamming weighted differences to perform a practical, key dependent, differential attack on ICE. The main conclusion is that the keyed permutation is not as effective as it was conjectured to be. 1 The ICE Algorithm ICE [7], which stands for Information Concealment Engine, is a 64-bit Feistel block cipher with a structure similar to DES, the Data Encryption Standard [5]. The standard ICE algorithm takes a 64-bit key and uses 16 subkeys in 16 rounds. There is a fast variant, Thin-ICE, which uses 8 rounds with a 64-bit key, and there are open-ended variants ICE-n which use 16n rounds and 64n-bit keys. Description of the round function The ICE round function F maps 32-bit inputs to 32-bit outputs, using a 60-bit subkey. ...

• Type: Conference
• Year: 1998
• Where: FSE
• Authors: Bart Van Rompay, Lars R. Knudsen, Vincent Rijmen
• Keywords: 64-bit, 64-bit Key, Cryptology, FSE 1998, Keyed Permutation