Dulal C. Kar

A CORDIC-based unified systolic architecture for sliding window applications of discrete transforms

A CORDIC-based, unified systolic architecture for sliding window applications of the discrete Fourier transform (DFT), the discrete Hartley transform (DHT), the discrete cosine transform (DCT), and the discrete sine transform (DST) is proposed. Compared to earlier works, the proposed scheme offers significant reduction in hardware, particularly for DHT. For an N-point DHT, it requires only [N/2]+1 processing elements, each consisting of one CORDIC processor and two adders.

On the prime factor decomposition algorithm for the discrete sine transform

Presents a fast algorithm for computing the discrete sine transform (DST) when the transform size N is decomposable into mutually prime factors. Based on the Lee algorithm for the discrete cosine transform (DCT) and from the relations obtained between DST and DCT, a new set of input and output index mappings for DST is presented. >

A new systolic realization for the discrete Fourier transform

A systolic array for the discrete Fourier transform (DFT) is proposed. In comparison with previous schemes, the proposed scheme reduces the number of multipliers required almost by half and thus saves a considerable amount of hardware. >

A multi-threshold based audio steganography scheme

Human auditory system is highly sensitive that can detect or discriminate subtle changes in an audio. The direct least significant bit (LSB) substitution scheme, often used in image steganography, cannot be effective for audio steganography to provide secrecy needed for many audio applications, because the embedded secret bits in the LSBs of the audio samples in a silent or near silent segment of an audio can produce strong hissing noise when played. In this work, governed by an error criterion, we present a multi-threshold-based scheme for audio steganography. In order to evade detection by means of any statistical or perceptual analysis of the resultant audio, the threshold values are derived from an error criterion that can be used to limit the number of bits to be embedded in an audio sample. To defend against retrieval of bits by an adversary as well as to dissipate any pattern in the resultant audio, a scheme for chaotic distribution of the secret message bits in the cover audio is also proposed. In comparison with most recently proposed schemes in literature, our proposed scheme exhibits better performance against statistical and perceptual analysis for the same embedding capacity. Our proposed scheme can be used to increase the capacity of the cover audio in a controlled manner by adjusting the error criterion.

A new analog voltage sorter

An analog circuit for comparing and sorting two input voltages is described. Using the circuit as a basic unit, a four-input sorter is designed. A technique to determine which of the four inputs corresponds to (address of the input of) a given output is also presented. The procedure can be extended to design an n-input sorter. >

A Holistic Schema Matcher

The capability of matching the schemas of the databases has led to its wide use in e-commerce, data integration, and data warehousing. In this paper we develop a holistic schema matcher, which provides a match between two schemas by combining the match results from the element-level techniques as well as instance-level techniques. The experimental results demonstrate good performance of the proposed matcher.

Applied Cryptography for Security and Privacy in Wireless Sensor Networks

It is challenging to secure a wireless sensor network (WSN) because its inexpensive, tiny sensor nodes do not have the necessary processing capability, memory capacity, and battery life to take advantage of the existing security solutions for traditional networks. Existing security solutions for wireless sensor networks are mostly based on symmetric key cryptography with the assumption that sensor nodes are embedded with secret, temporary startup keys before deployment thus avoiding any use of computationally demanding public key algorithms altogether. However, symmetric key cryptography alone cannot satisfactorily provide all security needs for wireless sensor networks. It is still problematic to replenish an operational wireless sensor network with new sensor nodes securely. Current research on public key cryptography for WSNs shows some promising results, particularly in the use of elliptic curve cryptography and identity based encryption for WSNs. Although security is essential for WSNs, it can complicate some crucial operations of a WSN like data aggregation or in-network data processing that can be affected by a particular security protocol. Accordingly, in this paper, we summarize, discuss, and evaluate recent symmetric key based results reported in literature on sensor network security protocols such as for key establishment, random key pre-distribution, data confidentiality, data integrity, and broadcast authentication as well as expose limitations and issues related to those solutions for WSNs. We also present significant advancement in public key cryptography for WSNs with promising results from elliptic curve cryptography and identity based encryption as well as their limitations for WSNs.