Differential Cryptanalysis of the ICE Encryption Algorithm

Abstract

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.

Controlled elements for designing ciphers suitable to efficient VLSI implementation

“…In such applications of PNs the permutation on data bit strings is a linear operation. Such use of PNs has been shown [5] to be not very effective against differential cryptanalysis. It seems [10] that cryptology can significantly benefit from the use of PNs to perform DataDependent (DD) Permutations (DDPs), since such permutations are variable.…”

Impossible Differential Cryptanalysis of Zodiac

“…For these reasons, block ciphers have been designed to consider the differential cryptanalysis since the middle of 1990's. Differential cryptanalysis has also been advanced variously -Conditional Differential Cryptanalysis [1,9], Truncated Differential Cryptanalysis [5], Impossible Differential Cryptanalysis [2], Higher Order Differential Cryptanalysis [5,6,8], Boomerang attack [11], and so on.…”