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Improved Linear Consistency Attack on Irregular Clocked Keystream Generators [chapter]

Håvard Molland
2004 Lecture Notes in Computer Science  
In this paper we propose a new attack on a general model for irregular clocked keystream generators.  ...  The model consists of two feedback shift registers of lengths l1 and l2, where the first shift register produces a clock control sequence for the second.  ...  Matthew Parker for helpful discussions and for reading and helping me in improving this paper.  ... 
doi:10.1007/978-3-540-25937-4_8 fatcat:gmakzqhcqvbefpstbsanqnri2u

LILI Keystream Generator [chapter]

Leonie Ruth Simpson, E. Dawson, Jovan Dj. Golić, William L. Millan
2001 Lecture Notes in Computer Science  
The design is simple and scalable, based on two binary linear feedback shift registers combined in a simple way, using both irregular clocking and nonlinear functions.  ...  A family of keystream generators, called the LILI keystream generators, is proposed for use in stream cipher applications and the security of these generators is investigated with respect to currently  ...  As correlation attacks have been successful against keystream generators based on either a nonlinear function of regularly clocked LFSR sequences [16, 14] or on irregular clocking of LFSRs [6, 17] ,  ... 
doi:10.1007/3-540-44983-3_18 fatcat:ukgvydtsargblovyzpvwobboy4

Security and performance analysis of SCDSP

Fardous Mohamed Eljadi, Imad Fakhri Al-Shaikhli
2016 International Journal on Perceptive and Cognitive Computing  
There are few approaches that attempt to add dynamicity to the structure of stream ciphers in order to improve their security level. SCDSP is a dynamic stream cipher that based on these approaches.  ...  It uses dynamic structure and parameters to increase the complexity of the cipher to improve its security level. The dynamic parameters are specified using bits from the secret key.  ...  Moreover, two types of irregular clocking are used. Distinguishing Attacks.  ... 
doi:10.31436/ijpcc.v2i1.33 fatcat:5jvdbijgzfcvnl4vmv4277gvlm

On the security of shift register based keystream generators [chapter]

Jovan Dj. Golić
1994 Lecture Notes in Computer Science  
Security against divide and conquer correlation attacks of binary keystream generators based on regularly or irregularly clocked shift registers combined by a function with or without memory is discussed  ...  Finally, it is interesting to note that besides the irregular clocking, one may also introduce the irregular interleaving of two or more individual keystream generators in order to obtain the output sequence  ...  , on the linear consistency test Zeng, Yang, Rao [42] , Anderson [2] .  ... 
doi:10.1007/3-540-58108-1_12 fatcat:yru4l7w53bgxfir3k4p3d63ave

Cryptanalysis of the DECT Standard Cipher [chapter]

Karsten Nohl, Erik Tews, Ralf-Philipp Weinmann
2010 Lecture Notes in Computer Science  
The DECT Standard Cipher (DSC) is a proprietary 64-bit stream cipher based on irregularly clocked LFSRs and a non-linear output combiner.  ...  Beyond disclosing the DSC, the paper proposes a practical attack against DSC that recovers the secret key from 2 15 keystreams on a standard PC with a success rate of 50% within hours; somewhat faster  ...  In these pre-cipher rounds, the irregular clock control is used but the output is discarded.  ... 
doi:10.1007/978-3-642-13858-4_1 fatcat:czybpkk2vfdj7euccfrudbk6he

Initialisation flaws in the A5-GMR-1 satphone encryption algorithm

V. Bhartia, L. Simpson
2016 Proceedings of the Australasian Computer Science Week Multiconference on - ACSW '16  
The design is based on four linear feedback shift registers, three of which are irregularly clocked.  ...  These features increase the effectiveness of generic time-memory tradeoff attacks on the cipher, making such attacks feasible.  ...  ATTACKING A5-GMR1 In this section we discuss several simple attacks on the A5-GMR1 keystream generator.  ... 
doi:10.1145/2843043.2843357 dblp:conf/acsc/BhartiaS16 fatcat:m4xyk6hhrja7fc4d3gutypvgiy

FPGA Implementation of an Improved Attack against the DECT Standard Cipher [chapter]

Michael Weiner, Erik Tews, Benedikt Heinz, Johann Heyszl
2011 Lecture Notes in Computer Science  
The attack consists of two phases: At first, the keystreams are analyzed to build up an underdetermined linear equation system.  ...  Our improvement to the first phase of the attack is able to more than double the success probability of the attack, depending of the number of available keystreams.  ...  After key loading, 40 blank rounds are performed using irregular clocking.  ... 
doi:10.1007/978-3-642-24209-0_12 fatcat:76jjl2gur5b55dtoaqovpgcste

Another attack on A5/1

P. Ekdahl, T. Johansson
2003 IEEE Transactions on Information Theory  
This paper presents a completely different attack on A5/1, based on ideas from correlation attacks.  ...  Several time-memory trade-off attacks against A5/1 have been proposed, most notably the recent attack by Biryukov, Shamir and Wagner, which can break A5/1 in seconds using huge precomputation time and  ...  The complexity of the attack is only linear in the length of the shift registers and depends instead on the number of irregular clockings before the keystream is produced.  ... 
doi:10.1109/tit.2002.806129 fatcat:mqipvv4ibvgoxp4fpcmfyt36au

Two Trivial Attacks on A5/1:A GSM Stream Cipher [article]

Ashish Jain, Narendra S. Chaudhari
2013 arXiv   pre-print
In this paper we compared previous attacks on A5/1 as well as an algebraic attack and a new improved guess and determine attack is proposed.  ...  Algebraic attacks are new and very powerful tool to cryptanalyse LFSRs based stream ciphers even non-linear combiner are concerned.  ...  we are considering irregular clocking of registers for generating equations.  ... 
arXiv:1305.6817v3 fatcat:siyyt3qykrfn3fk7f42bzw2ece

Towards Fast Correlation Attacks on Irregularly Clocked Shift Registers [chapter]

Jovan Dj. Golić
1995 Lecture Notes in Computer Science  
A theoretical framework for fast correlation attacks on irregularly clocked linear feedback shift registers (LFSRs) based on a recently established linear statistical weakness of decimated LFSR sequences  ...  The procedure is based on appropriately defmed parity-check sums and consists in iterative recomputation of the posterior probabilities for unknown elements of the decimation sequence.  ...  Linear Statistical Weakness Consider a clock-controlled shift register as a keystream generator consisting of a binary linear feedback shift register (LFSR) that is irregularly clocked according to a nonnegative  ... 
doi:10.1007/3-540-49264-x_20 fatcat:cyeubs5korgyxhfwuvmzj6qeoq

Cryptanalysis of alternating step generators

Robert Wicik, Rafal Gliwa, Piotr Komorowski
2015 2015 International Conference on Military Communications and Information Systems (ICMCIS)  
Alternate clocking of linear feedback shift registers is the popular technique used to increase the linear complexity of binary sequences produced by keystream generators designed for stream ciphers.  ...  The analysis of the best known attacks on the alternating step generator led us to add nonlinear filtering functions and the nonlinear scrambler to the construction.  ...  The alternating step generator (ASG) [4] is an example of the keystream generator, where the de Bruijn sequence [1] controls irregular clocking of two linear feedback shift registers.  ... 
doi:10.1109/icmcis.2015.7158683 fatcat:ap63hp5kpbhyzmwkhnnx5srlwu

Evolutionary approach to secure mobile telecommunication networks

Abdelkader Ghazli, Adda Alipacha, Naima Hadj Said
2021 Indonesian Journal of Electrical Engineering and Computer Science  
These algorithms are essentially composed of shift registers with linear feedback, controlled generally by a function or with another register in order to favor the randomness character of the keystream  ...  Our technique does not alter the A5/1's architecture, but it does help to improve its shifting system by an evolutionary approach, which guarantees the quality of the keystream generated and makes it more  ...  The attack has a high success rate of over 70%, yet the assault's complexity is merely linear in the length of the shift registers, relying instead on the number of irregular clocks before the keystream  ... 
doi:10.11591/ijeecs.v24.i1.pp357-366 fatcat:xfhglsj7nbh33lupsyoaf6r6r4

An Improved Correlation Attack Against Irregular Clocked and Filtered Keystream Generators [chapter]

Håvard Molland, Tor Helleseth
2004 Lecture Notes in Computer Science  
In this paper we propose a new key recovery attack on irregular clocked keystream generators where the stream is filtered by a nonlinear Boolean function.  ...  We show that the attack is much more efficient than expected from previous analytic methods, and we believe it improves all previous attacks on the cipher model.  ...  Our attack is not designed to attack the data generator subsystem only, but is especially aimed at irregular clocked and filtered keystream generators as one system.  ... 
doi:10.1007/978-3-540-28628-8_23 fatcat:3rpfba2wgrew7brigjkcirjwmm

Fast Implementation of KCipher-2 for Software and Hardware

Yuto NAKANO, Kazuhide FUKUSHIMA, Shinsaku KIYOMOTO, Tsukasa ISHIGURO, Yutaka MIYAKE, Toshiaki TANAKA, Kouichi SAKURAI
2014 IEICE transactions on information and systems  
The fastest algorithm is SNOW 2.0 and KCipher-2 is the second fastest despite the complicated irregular clocking mechanism.  ...  It consists of two feedback shift registers and a non-linear function. The size of each register in KCipher-2 is 32 bits and the non-linear function mainly applies 32-bit operations.  ...  KCipher-2 applies an irregular clocking mechanism to increase its non-linearity and hence its security.  ... 
doi:10.1587/transinf.e97.d.43 fatcat:pacd55be4nbybizshdvxeho2ai

Conditional Estimators: An Effective Attack on A5/1 [chapter]

Elad Barkan, Eli Biham
2006 Lecture Notes in Computer Science  
Irregularly-clocked linear feedback shift registers (LFSRs) are commonly used in stream ciphers. We propose to harness the power of conditional estimators for correlation attacks on these ciphers.  ...  Conditional estimators compensate for some of the obfuscating effects of the irregular clocking, resulting in a correlation with a considerably higher bias.  ...  Introduction Correlation attacks are one of the prominent generic attacks on stream ciphers.  ... 
doi:10.1007/11693383_1 fatcat:cfy347rfiray3bmulmygejjkga
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