Ciphertext-only attacks and weak long-term keys in T-310

T-310 is an important Cold War cipher (Schmeh 2006 Schmeh, K. 2006. The East German encryption machine T-310 and the algorithm it used. Cryptologia, 30(3):251–257.[Taylor &; Francis Online] , [Google Scholar]). It was the principal encryption algorithm used to protect various state communication lines in Eastern Germany in the 1980s. The cipher is quite robust, and it outputs extremely few bits from the internal state. In this article, the authors study the choice of the long-term key in T-310. They show that if a key is faulty, for example if they omit to check just one condition which the keys should satisfy, and more or less each time the round function is not bijective, communications can be decrypted in a ciphertext-only scenario. The authors provide mathematical proofs that the main historical key classes KT1 and KT2 are secure against such attacks.     

A parallel time-memory tradeoff attack on the Hill cipher

Leap et al. (2016 Leap, T., T. McDevitt, K. Novak, and N. Siermine. 2016. Further improvements to the Bauer-Millward attack on the Hill cipher. Cryptologia 40:1–16.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) reduced the time complexity of the Bauer-Millward (2007 Bauer, C., and K. Millward. 2007. Cracking matrix encryption row by row. Cryptologia 31(1):76–83.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) ciphertext-only attack on the Hill cipher from 𝒪(Lⁿ) to 𝒪(L^n?1), where L is the length of the alphabet, and n is the block size. This article presents an attack that reduces the complexity to 𝒪(L^n?1?s), 0?≤?s?≤?n???1. The practical limitation on the size of s is the memory available on the computer being used for the attack. Specifically, the computer must be able to hold L^s integer arrays of length N, where N is the number of blocks of ciphertext. The key idea is not to iterate over potential rows of the decryption matrix, but to iterate over randomly chosen characters in the plaintext. This attack also admits a straightforward parallel implementation on multiple processors to further decrease the run time of the attack.     

Comment on ‘Persistent inputs and the standard H2-multivariable control problem’ by K. Park and J.J. Bongiorno Jr

It is necessary to welcome the publication of the paper by Park and Bongiorno Jr (Park, K. and Bongiorno Jr, J.J. (2009 Park, K and Bongiorno Jr, JJ. 2009. Persistent Inputs and the Standard H₂-multivariable Control Problem. International Journal of Control, 82: 2002–2012. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]), ‘Persistent Inputs and the Standard H₂-multivariable Control Problem’, International Journal of Control, 82, 2002–2012) in which the special cases in H₂-optimisation problems are considered. However, for correct orientation of readers we would like to note some publications which, in our opinion, are connected to a problem given by Park and Bongiorno Jr (2009 Park, K and Bongiorno Jr, JJ. 2009. Persistent Inputs and the Standard H₂-multivariable Control Problem. International Journal of Control, 82: 2002–2012. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]), but are absent there.     

Continuous-time non-linear flatness-based predictive control: an exact feedforward linearisation setting with an induction drive example

A general flatness-based framework for non-linear continuous-time predictive control is presented. It extends the results of Fliess and Marquez (2000 Fliess, M and Marquez, R. 2000. Continuous-time Linear Predictive Control and Flatness: A Module-theoretic Setting with Examples. International Journal of Control, 73: 606–623. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) to the non-linear case. The mathematical setting, which is valid for multivariable systems, is provided by the theory of flatness-based exact feedforward linearisation introduced by the authors (Hagenmeyer and Delaleau 2003b Hagenmeyer, V and Delaleau, E. 2003b. Exact Feedforward Linearization Based on Differential Flatness. International Journal of Control, 76: 537–556. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]). Thereby differential flatness does not only yield an easy calculation of the predicted trajectories considering the respective system constraints, but allows to use simple linear feedback parts in a two-degree-of-freedom control structure. Moreover, this formalism permits one to handle non-minimum phase systems, and furthermore to deal with parameter uncertainties and exogenous perturbations. Respective robustness analysis tools are available. Finally, an induction drive example is discussed in detail and experimental results for this fast electro-mechanical system are presented.     

Two truck travelling salesman simulation

There are many algorithms currently available to approximate solutions to the ‘travelling salesman’ problem of finding the shortest route connecting n points in a complete tour. Conley (1988 CONLEY , W. C. , ( 1988 ), Int. J. Systems Sei. , 19 , 2115 .[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) presents a multi–stage simulation on a rank ordered distance array to solve a one vehicle problem for n = 20. A modification of that approach is presented here to deal with sending out two delivery trucks (or one truck making two trips) to touch all n points and return. An example for n = 33 is developed. The multi–stage simulation approach is then compared with other techniques.     

FROM THE ARCHIVES: CODETALKERS NOT WANTED

Abstract

The Hill Cipher, also known as matrix encryption, uses matrices to encipher and decipher text. Various attacks, such as those found by Jack Levine [2 Levine , J. 1961 . “Some Applications of High-Speed Computers to the Case n = 2 of Algebraic Cryptography,” Mathematics of Computation , 15 ( 75 ). [Google Scholar] 3 Levine , J. 1961 . “Some Elementary Cryptanalysis of Algebraic Cryptography,” American Mathematical Monthly , 68 ( 5 ): 411 – 418 .[Taylor &; Francis Online] , [Google Scholar] 5 Levine , J. and R. Chandler . 1989 . “The Hill Cryptographic System with Unknown Cipher Alphabet but Known Plaintext,” Cryptologia , 13 ( 1 ): 1 – 28 .[Taylor &; Francis Online] , [Google Scholar]], have been published for this system. This article reviews a few previous results and presents a powerful new attack in which the rows of the matrix can be determined independent of one another, greatly reducing the amount of time needed for decipherment.     

Comment on ‘Optimal inventory replenishment policy for the EPQ model under trade credit derived without derivatives’

In this article, we complement the shortcoming of the inventory economic production quantity (EPQ) model developed by Huang and Huang (2008 Huang, YF and Huang, HF. 2008. Optimal Inventory Replenishment Policy for the EPQ Model Under Trade Credit Derived Without Derivatives. International Journal of Systems Science, 39: 539–546. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]), ‘Optimal Inventory Replenishment Policy for the EPQ Model Under Trade Credit Derived Without Derivatives’, International Journal of Systems Science, 39, 539–546), and propose an arithmetic–geometric inequality method to obtain the global optimal solution without taking complex differential calculus or using tedious algebraic manipulations. Finally, we provide an economical interpretation of the theoretical result so that the reader can understand the insight of the result.     

Approximation error in PDE-based modelling of vehicular platoons

We study the problem of how much error is introduced in approximating the dynamics of a large vehicular platoon by using a partial differential equation, as was done in Barooah, Mehta, and Hespanha [Barooah, P., Mehta, P.G., and Hespanha, J.P. (2009 Barooah, P, Mehta, PG and Hespanha, JP. 2009. Mistuning-based Decentralised Control of Vehicular Platoons for Improved Closed Loop Stability. IEEE Transactions on Automatic Control, 54: 2100–2113. [Crossref], [Web of Science ®] , [Google Scholar]), ‘Mistuning-based Decentralised Control of Vehicular Platoons for Improved Closed Loop Stability’, IEEE Transactions on Automatic Control, 54, 2100–2113], Hao, Barooah, and Mehta [Hao, H., Barooah, P., and Mehta, P.G. (2011), ‘Stability Margin Scaling Laws of Distributed Formation Control as a Function of Network Structure’, IEEE Transactions on Automatic Control, 56, 923–929]. In particular, we examine the difference between the stability margins of the coupled-ordinary differential equations (ODE) model and its partial differential equation (PDE) approximation, which we call the approximation error. The stability margin is defined as the absolute value of the real part of the least stable pole. The PDE model has proved useful in the design of distributed control schemes (Barooah et al. 2009 Barooah, P, Mehta, PG and Hespanha, JP. 2009. Mistuning-based Decentralised Control of Vehicular Platoons for Improved Closed Loop Stability. IEEE Transactions on Automatic Control, 54: 2100–2113. [Crossref], [Web of Science ®] , [Google Scholar]; Hao et al. 2011 Hao, H, Barooah, P and Mehta, PG. 2011. Stability Margin Scaling Laws of Distributed Formation Control as a Function of Network Structure. IEEE Transactions on Automatic Control, 56: 923–929. [Crossref], [Web of Science ®] , [Google Scholar]); it provides insight into the effect of gains of local controllers on the closed-loop stability margin that is lacking in the coupled-ODE model. Here we show that the ratio of the approximation error to the stability margin is O(1/N), where N is the number of vehicles. Thus, the PDE model is an accurate approximation of the coupled-ODE model when N is large. Numerical computations are provided to corroborate the analysis.     

A continuous review inventory model with controllable backorder rate and investments

In this study, we investigate a continuous review inventory model to reduce lead time, yield variability and setup cost simultaneously through capital investments. We assume that the backorder rate is depending on the length of the lead time through the amount of shortages. We also assume that lead time demand's distribution is not known but its first and second moments are known. We apply minimax distribution free procedure to minimise the expected total annual cost. By using logarithmic investment function we describe the relationship between the reduction in lead time, yield variability and setup cost with capital investment. This function was used in many existing models. Our main aim is to determine the optimal capital investment and ordering policies that minimises the expected total annual cost. To find out the optimal solution, an algorithm is given. With the help of this algorithm, optimal capital investment and ordering policies are wrought out. Numerical examples are given to elucidate the model. Our proposed model greatly differs from the model existing in the literature (the model by Lin and Hou (2005 Lin, LC and Hou, KL. 2005. An Inventory System with Investment to Reduce Yield Variability and Setup Cost. Journal of the Operational Research Society, 56: 67–74. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar])) viz: (1) In the above model, yield variability and setup cost were reduced through capital investment. In our model we reduce yield variability setup cost and also the lead time, which plays a vital role in any business. By reducing lead time we can improve the service level to the customer so as to increase the competitive edge in business. (2) In the model (the model by Lin and Hou (2005 Lin, LC and Hou, KL. 2005. An Inventory System with Investment to Reduce Yield Variability and Setup Cost. Journal of the Operational Research Society, 56: 67–74. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar])), it was assumed that lead time demand follows normal distribution. But in our model we take the distribution of lead time demand as distribution free. That is, it can follow any distribution which is more general. (3) In the above model (the model by Lin and Hou (2005 Lin, LC and Hou, KL. 2005. An Inventory System with Investment to Reduce Yield Variability and Setup Cost. Journal of the Operational Research Society, 56: 67–74. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar])), shortages are completely backlogged. But we consider partial backlogging and take the backlogging rate as 0 ≤ B ≤ 1. If we set backlogging rate B = 1 we get the above model. That is, the above model is particular case of our model. (4) We also assume that the backorder rate depends on the length of the lead time through the amount of shortages. If the lead time is longer then shortage accumulation is higher. The patience of customers will result in failure in business since some customers may turn to some other supplier. Hence, the backorder rate will be reduced. This assumption is very realistic.     

Knowledge processes in virtual teams: consolidating the evidence

This article takes stock of the current state of research on knowledge processes in virtual teams (VTs) and consolidates the extent research findings. Virtual teams, on the one hand, constitute important organisational entities that facilitate the integration of diverse and distributed knowledge resources. On the other hand, collaborating in a virtual environment creates particular challenges for the knowledge processes. The article seeks to consolidate the diverse evidence on knowledge processes in VTs with a specific focus on identifying the factors that influence the effectiveness of these knowledge processes. The article draws on the four basic knowledge processes outlined by Alavi and Leidner (2001 Alavi, M.Leidner, D.E., 2001. Review: knowledge management and knowledge management systems: conceptual foundations and research issues. MIS Quarterly, 25 (1), 107–136. doi: 10.2307/3250961[Crossref], [Web of Science ®] , [Google Scholar]) (i.e. creation, transferring, storage/retrieval and application) to frame the investigation and discuss the extent research. The consolidation of the existing research findings allows us to recognise the gaps in the understanding of knowledge processes in VTs and identify the important avenues for future research.     

A FORMALISM FOR A CASE STUDY IN THE WATERTIME PROJECT: THE CITY WATER SYSTEM IN GRENOBLE,FROM PRIVATIZATION TO REMUNICIPALIZATION

The formal representation for legal or other narratives as introduced by Nissan (2001 Nissan, E. 2001. A formalism for competing claims of identification: The “Smemorato di Collegno” amnesia case. Informatics and Computing, 20(6): 625–656. [Web of Science ®] , [Google Scholar]; ; 2003a Nissan, E. 2003a. Identification and doing without it, I: A situational classification of misapplied personal identity, with a formalism for a case of multiple usurped identity in Marivaux. Cybernetics and Systems, 34(4–5): 317–358. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]; 2003b Nissan, E. 2003b. Identification and doing without it, II: Visual evidence for pinpointing identity. How Alexander was found out: Purposeful action, enlisting support, assumed identity, and recognition. A goal-driven formal analysis. Cybernetics and Systems, 34(4–5): 359–380. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]; 2003d Nissan, E. 2003c. Identification and doing without it, III: Authoritative opinions, purposeful action, relabelled goods, and forensic examinations. The case of the stuffed birds: Its narrative dynamics set in formulae. Cybernetics and Systems, 34(6–7): 467–500. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]; 2003a Nissan, E. 2003a. Identification and doing without it, I: A situational classification of misapplied personal identity, with a formalism for a case of multiple usurped identity in Marivaux. Cybernetics and Systems, 34(4–5): 317–358. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar] is adapted to the analysis of a case study in WaterTime, a project developed by David Hall and his collaborators in view of the development of a decision model for policy making, concerning the privatization of city water systems throughout the European Union. In WaterTime, the experience of several cities is analyzed and compared. In particular, have analyzed the privatization, in 1989, of the city water system in Grenoble, France. Eventually, corruption was proven, and the system was partly remunicipalized; court decisions led to its full remunicipalization. We sketch a symbolic representation of events in this narrative.     

Adaptive learning control design for robotic manipulators driven by permanent magnet synchronous motors

On the basis of the ideas recently presented in Tomei and Verrelli (Tomei, P., and Verrelli, C.M. (2010 Tomei, P and Verrelli, CM. 2010. Learning Control for Induction Motor Servo Drives with Uncertain Rotor Resistance. International Journal of Control, 83: 1515–1528. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]), ‘Learning Control for Induction Motor Servo Drives with Uncertain Rotor Resistance’, International Journal of Control, 83, 1515–1528) and Marino et al. (Marino, R., Tomei, P., and Verrelli, C.M. (2011 Marino, R, Tomei, P and Verrelli, CM. 2011. Robust Adaptive Learning Control for Nonlinear Systems with Extended Matching Unstructured Uncertainties. International Journal of Robust and Nonlinear Control, Early View, doi: 10.1002/rnc.1720 [Google Scholar]), ‘Robust Adaptive Learning Control for Nonlinear Systems with Extended Matching Unstructured Uncertainties’, International Journal of Robust and Nonlinear Control, Early View, doi: 10.1002/rnc.1720), we briefly show how the adaptive learning control design proposed in Liuzzo and Tomei (Liuzzo, S., and Tomei, P. (2009 Liuzzo, S and Tomei, P. 2009. Global Adaptive Learning Control of Robotic Manipulators by Output Error Feedback. International Journal of Adaptive Control and Signal Processing, 23: 97–109.  [Google Scholar]), Global Adaptive Learning Control of Robotic Manipulators by Output Error Feedback, International Journal of Adaptive Control and Signal Processing, 23, 97–109) can be extended to robotic manipulators driven by nonsalient-pole (surface) permanent magnet synchronous motors. Unstructured uncertain dynamics (that is no parameterisation is available for the uncertainties) of the rigid robot with rotational joints are considered as well as uncertainties in stator resistances of the synchronous motors are taken into account. Two solutions with clear stability proofs are presented: a global decentralised control via state feedback and a semi-global control via output feedback. Output tracking of known periodic reference signals and learning of corresponding uncertain input reference signals are achieved. Available results in the literature are thus improved since no simplification concerning negligible electrical motor dynamics is used.     

A note on ‘a replenishment policy for items with price-dependent demand,time-proportional deterioration and no shortages’

In a recent paper, Begum et al. (2012 Begum, R., Sahoo, R.R., and Sahu, S.K. (2012), ‘A Replenishment Policy for Items with Price-Dependent Demand, Time-Proportional Deterioration and no Shortages’, International Journal of Systems Science, 43, 903–910.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar], International Journal of Systems Science, 43, 903–910) established pricing and replenishment policy for an inventory system with price-sensitive demand rate, time-proportional deterioration rate which follows three parameters, Weibull distribution and no shortages. In their model formulation, it is observed that the retailer's stock level reaches zero before the deterioration occurs. Consequently, the model resulted in traditional inventory model with price sensitive demand rate and no shortages. Hence, the main purpose of this note is to modify and present complete model formulation for Begum et al. (2012) Begum, R., Sahoo, R.R., and Sahu, S.K. (2012), ‘A Replenishment Policy for Items with Price-Dependent Demand, Time-Proportional Deterioration and no Shortages’, International Journal of Systems Science, 43, 903–910.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]. The proposed model is validated by a numerical example and the sensitivity analysis of parameters is carried out.     

Work-Domain Experts as Evaluators: Usability Inspection of Domain-Specific Work-Support Systems

Work on how consumers evaluate electronic service quality is both topical and important due to the well-accepted criticality of electronic channels in selling products and services. However, most of the relevant research on electronic research quality is preoccupied with the website Internet context and most of the studies are single-country studies, inhibiting conclusions of generalizibility. Theoretically rooted in the Nordic Model of perceived service quality, this exploratory study uses an e-service quality scale to measure mobile Internet service quality in different national settings. Consistent with the available e-service quality literature, results indicate that e-service quality is a second-order factor, with three reflective first-order dimensions: efficiency, outcome, and customer care. Most important, cross-validation investigations using samples drawn from Korean, Hong Kong, and Japanese mobile Internet user populations, support the factorial structure invariance of the construct. Following Cheung and Reynolds's (2002) Cheung, G. W. and Rensvold, R. B. 2002. Evaluating goodness-of-fit indexes for testing measurement invariance. Structural Equation Modeling, 9: 233–255. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar] suggestions, factor means differences between the three countries contributing to the scarce cross-national electronic service quality literature are tentatively examined. These initial empirical findings imply that although consumers in different countries use the same dimensions to evaluate mobile Internet services, importance weightings assigned on these dimension are probably not the same.     

A numerical algorithm to find soft-constrained Nash equilibria in scalar LQ-games

This paper provides a numerical algorithm to calculate all soft-constrained Nash equilibria in a regular scalar indefinite linear-quadratic game. The algorithm is based on the calculation of the eigenstructure of a certain matrix. The analysis follows the lines of the approach taken by Engwerda (2003 Engwerda, JC. 2003. Solving the scalar feedback Nash algebraic Riccati equations: an eigenvector approach. IEEE Trans. Automat. Contr., 48: 847–853. [Crossref] , [Google Scholar]) to calculate the solutions of a set of scalar coupled feedback Nash algebraic Riccati equations.     

Are mobile phone conversations always so annoying? The ‘need-to-listen’ effect re-visited

According to Monk et al. (2004a Monk, A.F., et al., 2004a. Why are mobile phones annoying? Behaviour & Information Technology, 23 (1), 33–42. doi: 10.1080/01449290310001638496[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]. Why are mobile phones annoying? Behaviour and Information Technology, 23 (1), 33–42), mobile phone conversations are annoying to overhear due to an involuntary need-to-listen in order to predict the inaudible half of the conversation. However, previous support for this need-to-listen explanation of annoyance has failed to consider the confound that mobile phone conversations also have less predictable acoustic patterns and has only investigated ‘neutral’ conversations. By staging mobile and face-to-face conversations in public, this study further supports the need-to-listen explanation. By removing the need-to-listen to the content of a mobile conversation through introducing foreign speech, bystanders no longer perceived the conversation as more annoying than a conversation between two co-present individuals, supporting the need-to-listen explanation over unpredictable acoustics. In two further experiments manipulating conversational content (‘neutral’ vs. ‘intriguing’), findings suggest that the need-to-listen to mobile phone conversations is not inherently annoying; it can be annoying or possibly even ‘interesting’ depending on the conversational content.     

An Improvised ECC Mechanism with Probabilistic Approach

ABSTRACT

Elliptic curve cryptography provides a secure means of exchanging keys among communicating hosts using the Diffie-Hellman Key Exchange algorithm. Encryption and decryption of texts and messages have also been attempted. In Ramasamy, Prabakar, Devi, and Suguna (2009) Rajaram Ramasamy, R., Amutha Prabakar, M., Indra Devi, M. and Suguna, M. 2009. Knapsack based ECC encryption and decryption. International Journal of Network Security, 9(3) November: 218–226.  [Google Scholar],,the authors presented the implementation of ECC by first transforming the message into an affine point on the EC and then applying the knapsack algorithm on ECC encrypted message over the finite field GF(p). The authors in their decryption process used elliptic curve discrete logarithm to get back the plain text. This may form a computationally infeasible problem if the values are large enough in generating the plain text. In Krishna (2011 Krishna, A.V.N. 2011. Probabilistic encryption based ECC mechanism. International Journal on Advancements in Technology(IJOAT), 2(2) January: 257–268.  [Google Scholar]), the author mapped the basin value randomly on the output of ECC to generate the cipher text. In the present work the output of ECC algorithm is iterated by the values which are randomly picked from the basin values to provide a probabilistic approach to the output which makes the algorithm free from the chosen cipher text attack. Thus by having key lengths of even much less than 160 bits, the present algorithm provides sufficient strength against crypto analysis and whose performance can be compared with standard algorithms such as RSA.