The family of stream ciphers MICKEY (which stands for Mutual Irregular Clocking KEYstream generator) is aimed at resource-constrained hardware platforms. It is intended to have low complexity in hardware, while providing a high level of security. It uses irregular clocking of shift registers, with some novel techniques to balance the need for guarantees on period and pseudorandomness against the need to avoid certain cryptanalytic attacks.

The information in this document is provided as is, and no guarantee or warranty is given or implied that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and liability.

Hermes8 [6,7] is one of the stream ciphers submitted to the ECRYPT Stream Cipher Project (eSTREAM [3]). In this paper we present an analysis of the Hermes8 stream ciphers. In particular, we show an attack on the latest version of the cipher (Hermes8F), which requires very few known keystream bytes and recovers the cipher secret key in less than a second on a normal PC. Furthermore, we make some remarks on the cipher's key schedule and discuss some properties of ciphers with similar algebraic structure to Hermes8.

Hermes8 [4,5] is one of the stream ciphers submitted to the ECRYPT Stream Cipher Project (eSTREAM [2]). In this paper we present an attack on the latest version of the cipher (Hermes8F), which requires very few known keystream bytes and recovers the cipher secret key in less than a second on a normal PC.

Jansen introduced a technique for building LFSRs that can be clocked a large number of times with a single simple operation. These may be useful in the construction of stream ciphers based on clock-controlled LFSRs. However, for LFSR sizes of typical interest, it appears generally hard to find such jumping LFSRs with particular desired parameters. In this note we explain a trick which we used to find the jumping LFSRs in MICKEY and MICKEY-128, and which may be useful for future applications.

A new approach to attack A5/1 is proposed. The proposed attack is a refinement of a previous attack by Ekdahl and Johansson. We make two important observations that lead to a new attack with improved performance.

Sober-t16 and Sober-t32 are two synchronous stream ci- phersdevelopedbyG.RoseandP.HawkesandsubmittedtotheNESSIE competition.Inthispaperweshowhowaprobabilisticfactorinthede- signcanbeexploited.AGuessandDetermineattackismountedagainst Sober-tw.Forunstuttered Sober-t32,thisattackismoree-cientthan exhaustive key search. Keywords:NESSIE,Cryptanalysis,SecurityEvaluation, Sober-tw,Guess andDetermine attack.

MISTY1 is a block cipher whose design relies on an assertion of provable security against linear and difierential cryptanalysis. Yet, a simplified and round reduced version of MISTY1 that does not alter the security provability can be attacked with higher order difierential cryptanalysis. We managed to explain this attack by deriving the attacking property from the choice of an atomic component of the algorithm, namely one of the two MISTY1 S-boxes. This allowed us to classify the good and the bad S-boxes built with the same principles and to show that none of the S-boxes with optimal linear and difierential properties has an optimal behaviour with respect to higher order difierential cryptanalysis.

A new family of very fast stream ciphers called COS (for “crossing over system”) has been proposed by Filiol and Fontaine, and seems to have been adopted for at least one commercial standard. In this note we show that the COS ciphers are very weak indeed — it requires negligible effort to reconstruct the state of the keystream generator from a very small amount of known keystream.

A new family of very fast stream ciphers called COS (for “crossing over system”) has been proposed by Filiol and Fontaine, and seems to have been adopted for at least one commercial standard. COS(2,128) Mode I and COS(2,128) Mode II are particular members of this family for which the authors proposed a cryptanalysis challenge. The ciphers accept secret keys of 256, 192 or 128 bits. In this note we cryptanalyse both of these ciphers, using a small amount of known keystream — with negligible effort in the case of Mode II, and with effort well below that required for a single DES key search in the case of Mode I.

LILI-128 is a stream cipher that was submitted to NESSIE. Strangely, the designers do not really seem to have tried to ensure that cryptanalysis is no easier than by exhaustive key search. We show that there are indeed attacks faster than exhaustive key search. We also demonstrate a related key attack which has very low complexity, and which could be of practical significance if the cipher were used in a certain rather natural way.

Abstract: The ,stream cipher MICKEY (which stands for Mutual Irregular Clocking KEYstream generator) is aimed at resource-constrained hardware platforms. It is intended to have low complexity in hardware, while providing a high level of security. It uses irregular clocking of shift registers, with some,novel techniques to balance ,the need for guarantees on period ,and pseudorandomness, against the need to avoid certain cryptanalytic attacks. Keywords:MICKEY, stream cipher, ECRYPT, irregular clocking.

We present a strengthened version 2.0 of the stream cipher MICKEY. MICKEY (which stands for Mutual Irregular Clocking KEYstream generator) is aimed at resource-constrained hardware platforms. It is intended to have low complexity in hardware, while providing a high level of security. It uses irregular clocking of shift registers, with some novel techniques to balance the need for guarantees on period and pseudorandomness against the need to avoid certain cryptanalytic attacks.

The stream cipher MICKEY (which stands for Mutual Irregular Clocking KEYstream generator) is aimed at resource-constrained hardware platforms. It is intended to have low complexity in hardware, while providing a high level of security. It uses irregular clocking of shift registers, with some novel techniques to balance the need for guarantees on period and pseudorandomness against the need to avoid certain cryptanalytic attacks.