A cipher based on data-dependent permutations

Abstract

Data-dependent permutations (DDP) are introduced as basic cryptographic primitives to construct fast hardware-oriented ciphers. Some variants of the DDP operations and their application in the cipher CIKS-1 are considered. A feature of CIKS-1 is the use of both the data-dependent transformation of round subkeys and the keydependent DDP operations.

ARMADILLO: A Multi-purpose Cryptographic Primitive Dedicated to Hardware

“…3 Such functions rely on data-dependent bit transpositions [16]. Given a bitstring x = x 2k · · · x 1 , fixed permutations σ 0 and σ 1 over the set {1, 2, .…”

A differential attack on the CIKS-1 block cipher

“…Further information on the structure of the datadependent permutations found in CIKS-1 can be found in [3].…”

“…In the paper [3] the CIKS-1 authors make the claim that the number of plaintext pairs required for a differential attack on the cipher is in the order of 2 64 . This analysis is done by ignoring the internal key schedule and permutation P 1 and focusing on P 2 and P 6 (the P 32/80 permutations on the right hand side of the cipher).…”

“…If an analysis of the cipher is done not on strict differentials, but the hamming weight of differentials as they pass through the cipher, it is possible to construct an attack which has much lower complexity than the one in [3]. Three input differences weights were examined for relations to four output difference weights of interest.…”

“…In [3] a new cipher making heavy use of DDPs was introduced. CIKS-1, an 8-round block cipher, was designed for speed in hardware and uses the DDPs to provide nonlinearity while mixing key and data bits.…”