《State Space Cryptanalysis of The MICKEY Cipher》.pdf

State Space Cryptanalysis of The MICKEY Cipher Tor Helleseth , Cees J.A. Jansen , Oleksandr Kazymyrov and Alexander Kholosha The Selmer Center, Department of Informatics University of Bergen, P.O. Box 7800, N-5020 Bergen, Norway Email: Tor.Helleseth, Oleksandr.Kazymyrov, Alexander.Kholosha@ii.uib.no DeltaCrypto BV Riebeeckstraat 10, 5684ej Best, The Netherlands E-mail: cees.jansen@deltacrypto.nl Abstract—In this paper, we consider the key-stream generator The Mutual Irregular Clocking KEYstream generator MICKEY, whose internal state splits into two parts that are up- (MICKEY) is an example of the generators described above. dated both linearly and nonlinearly while clocking the generator. In article [2] Hong and Kim noted that the first version of These state update functions also depend on the internal state of the registers, which perform the so-called self-mutual control. MICKEY (MICKEY v1) is potentially vulnerable to time- We suggest several attack scenarios based on the reverse clocking memory-data (TMD) tradeoff attack [4], [9]. Based on this re- of the generator and analysis of the acquired backward states search, developers of the current (second) version of MICKEY tree. Furthermore, we show meet-in-the-middle attack can be (MICKEY v2) have modified the algorithm and shown that applied while simultaneously allowing the generation of shift