Sukumar Nandi

Theory and applications of cellular automata in cryptography

This paper deals with the theory and application of Cellular Automata (CA) for a class of block ciphers and stream ciphers. Based on CA state transitions certain fundamental transformations are defined which are block ciphering functions of the proposed enciphering scheme, These fundamental transformations are found to generate the simple (alternating) group of even permutations which in turn is a subgroup of the permutation group, These functions are implemented with a class of programmable cellular automata (PCA) built around rules 51, 153, and 195. Further, high quality pseudorandom pattern generators built around rule 90 and 150 programmable cellular automata with a rule selector (i.e., combining function) has been proposed as running key generators in stream ciphers, Both the schemes provide better security against different types of attacks. With a simple, regular, modular and cascadable structure of CA, hardware implementation of such schemes idealy suit VLSI implementation. >

Route Stability Based QoS Routing in Mobile Ad Hoc Networks

To provide high quality communications service among mobile wireless devices is basically a challenging task in wireless ad hoc networks. In this paper, we propose a Route Stability based QoS Routing (RSQR) protocol in Mobile Ad Hoc Networks (MANETs) which is an extension of QoS routing with throughput and delay constraints. Ensuring a data path to be valid for sufficiently longer period of time is a very difficult problem in MANET due to its highly dynamic nature. We propose a simple model for computing link stability and route stability based on received signal strengths. By including some extra fields in route request/reply packets, the route stability information can be utilized to select a route with higher stability among all the feasible routes between a given source destination pair. Further, inclusion of a signal strength based admission control enhances the performance of the routing. Results of our experiments show performance improvements in terms of packet delivery ratio, control overhead and average end-to-end delay in comparison with a QoS routing protocol proposed by Q. Xue and A. Ganz.

Comments on "Theory and applications of cellular automata in cryptography" [with reply]

The cipher systems based on Cellular Automata proposed by Nandi et al are a ne and are insecure Index Terms Cryptography block ciphers stream ciphers cellular automata

A new similarity measure using Bhattacharyya coefficient for collaborative filtering in sparse data

Collaborative filtering (CF) is the most successful approach for personalized product or service recommendations. Neighborhood based collaborative filtering is an important class of CF, which is simple, intuitive and efficient product recommender system widely used in commercial domain. Typically, neighborhood-based CF uses a similarity measure for finding similar users to an active user or similar products on which she rated. Traditional similarity measures utilize ratings of only co-rated items while computing similarity between a pair of users. Therefore, these measures are not suitable in a sparse data. In this paper, we propose a similarity measure for neighborhood based CF, which uses all ratings made by a pair of users. Proposed measure finds importance of each pair of rated items by exploiting Bhattacharyya similarity. To show effectiveness of the measure, we compared performances of neighborhood based CFs using state-of-the-art similarity measures with the proposed measured based CF. Recommendation results on a set of real data show that proposed measure based CF outperforms existing measures based CFs in various evaluation metrics.

Detecting ARP spoofing: an active technique

The Address Resolution Protocol (ARP) due to its statelessness and lack of an authentication mechanism for verifying the identity of the sender has a long history of being prone to spoofing attacks. ARP spoofing is sometimes the starting point for more sophisticated LAN attacks like denial of service, man in the middle and session hijacking. The current methods of detection use a passive approach, monitoring the ARP traffic and looking for inconsistencies in the Ethernet to IP address mapping. The main drawback of the passive approach is the time lag between learning and detecting spoofing. This sometimes leads to the attack being discovered long after it has been orchestrated. In this paper, we present an active technique to detect ARP spoofing. We inject ARP request and TCP SYN packets into the network to probe for inconsistencies. This technique is faster, intelligent, scalable and more reliable in detecting attacks than the passive methods. It can also additionally detect the real mapping of MAC to IP addresses to a fair degree of accuracy in the event of an actual attack.

Modeling the short-term unfairness of IEEE 802.11 in presence of hidden terminals

IEEE 802.11 exhibits both short-term and long-term unfairness. The short-term fairness automatically gives rise to long-term fairness, but not vice versa. When we thoroughly investigated a simple scenario with hidden terminals, we found it to be unfair on the short-term basis, though it provides fair access on a long-term basis. It implies that the protocol cannot be used to provide fair access for delay sensitive traffic even in a simple scenario. In this paper, we analyze the short-term behavior using the embedded-Markov chain method to answer the following two questions: (i) once a node gets control of the medium, what is the average number of packets this node can transmit consecutively without experiencing any collision, (ii) once a node loses its control of the medium, what is the average time the node has to wait before it gets control of the medium again. The first question reflects on how long a node can capture the medium, whereas the second question reflects on how long a node may be starved. The analytical model is validated by the simulation results. Our work is distinct from most of the work published in the literature in two aspects: we focus on the short-term behavior rather than the long-term, and the analytical method is adopted for the study.

Analysis of periodic and intermediate boundary 90/150 cellular automata

Considerable interest has been recently generated in the study of Cellular Automata (CA) behavior. Polynomial and matrix algebraic tools are employed to characterize some of the properties of null/periodic boundary CA. Some other results of group CA behavior have been reported based on simulation studies. This paper reports a formal proof for the conjecture-there exists no primitive characteristic polynomial of 90/150 CA with periodic boundary condition. For generation of high quality pseudorandom patterns, it is necessary to employ CA having primitive characteristic polynomial. There exist two null boundary CA for every primitive polynomial. However, for such Cs the quality of pseudorandomness suffers in general, particularly in the regions around the terminal cells because of null boundary condition. In this background, a new concept of intermediate boundary CA has been proposed to generate pseudorandom patterns that are better in quality than those generated with null boundary CA. Some interesting properties of intermediate boundary CA are also reported.

An Outlier Detection Method Based on Clustering

In this paper we propose a clustering based method to capture outliers. We apply K-means clustering algorithm to divide the data set into clusters. The points which are lying near the centroid of the cluster are not probable candidate for outlier and we can prune out such points from each cluster. Next we calculate a distance based outlier score for remaining points. The computations needed to calculate the outlier score reduces considerably due to the pruning of some points. Based on the outlier score we declare the top

Online Voting System Powered by Biometric Security Using Steganography

n

A Multipath QoS Routing with Route Stability for Mobile Ad Hoc Networks

points with the highest score as outliers. The experimental results using real data set demonstrate that even though the number of computations is less, the proposed method performs better than the existing method.