Papers by Sowmyan Kousthubadharan
Digital signal processing, Jan 1, 2000
In this paper we describe the major elements of MIT Lincoln Laboratory's Gaussian mixture model (... more In this paper we describe the major elements of MIT Lincoln Laboratory's Gaussian mixture model (GMM)-based speaker verification system used successfully in several NIST Speaker Recognition Evaluations (SREs). The system is built around the likelihood ratio test for verification, using simple but effective GMMs for likelihood functions, a universal background model (UBM) for alternative speaker representation, and a form of Bayesian adaptation to derive speaker models from the UBM. The development and use of a handset detector and score normalization to greatly improve verification performance is also described and discussed. Finally, representative performance benchmarks and system behavior experiments on NIST SRE corpora are presented.
Chaos, Solitons & Fractals, Jan 1, 2004
Encryption of images is different from that of texts due to some intrinsic features of images suc... more Encryption of images is different from that of texts due to some intrinsic features of images such as bulk data capacity and high redundancy, which are generally difficult to handle by traditional methods. Due to the exceptionally desirable properties of mixing and sensitivity to initial conditions and parameters of chaotic maps, chaos-based encryption has suggested a new and efficient way to deal with the intractable problem of fast and highly secure image encryption. In this paper, the two-dimensional chaotic cat map is generalized to 3D for designing a real-time secure symmetric encryption scheme. This new scheme employs the 3D cat map to shuffle the positions (and, if desired, grey values as well) of image pixels and uses another chaotic map to confuse the relationship between the cipher-image and the plain-image, thereby significantly increasing the resistance to statistical and differential attacks. Thorough experimental tests are carried out with detailed analysis, demonstrating the high security and fast encryption speed of the new scheme.
Circuits and Systems, 2002 IEEE International …, Jan 1, 2002
The security of digital images attracts much attention recently, and many image encryption method... more The security of digital images attracts much attention recently, and many image encryption methods have been proposed. In IS-CAS2000, a new chaotic key-based algorithm (CKBA) for image encryption was proposed. This paper points out CKBA is very weak to the chosen/known-plaintext attack with only one plainimage, and its security to brute-force ciphertext-only attack is overestimated by the authors. That is to say, CKBA is not secure at all from cryptographic viewpoint. Some experiments are made to show the feasibility of the chosen/known-plaintext attack. We also discuss some remedies to the original scheme and their performance, and we find none of them can essentially improve the security of CKBA.
Consumer Electronics, IEEE …, Jan 1, 2000
In the recent years, Internet multimedia applications have become very popular. Valuable multimed... more In the recent years, Internet multimedia applications have become very popular. Valuable multimedia content such as digital images, however, is vulnerable to unauthorized access while in storage and during transmission over a network. Streaming digital images also require high network bandwidth for transmission. For effective image transmission over Internet; therefore, both security and bandwidth issues must be considered. In this paper, we present a novel scheme, which combines Discrete Wavelet Transform (DWT) for image compression and block cipher Data Encryption Standard (DES) for image encryption. The simulation results indicate thaf our proposed method enhances the security for image transmission over the Internet as well as improves the transmission rate.
Chaos, Solitons & Fractals, Jan 1, 2007
In this paper, a fast chaos-based image encryption system with stream cipher structure is propose... more In this paper, a fast chaos-based image encryption system with stream cipher structure is proposed. In order to achieve a fast throughput and facilitate hardware realization, 32-bit precision representation with fixed point arithmetic is assumed. The major core of the encryption system is a pseudo-random keystream generator based on a cascade of chaotic maps, serving the purpose of sequence generation and random mixing. Unlike the other existing chaos-based pseudo-random number generators, the proposed keystream generator not only achieves a very fast throughput, but also passes the statistical tests of up-to-date test suite even under quantization. The overall design of the image encryption system is to be explained while detail cryptanalysis is given and compared with some existing schemes.
Optical Engineering, Jan 1, 1999
... In this paper, the proposed method is that the input image is encrypted by performing optical... more ... In this paper, the proposed method is that the input image is encrypted by performing optical XOR operations with the key bit stream. The input gray-level image should be converted to the binary image to perform XOR operations that are used as the encryption method in stream ...
Optics communications, Jan 1, 2000
... The calculation size of the hologram data is 512×512. ... We suppose an eavesdropper attempts... more ... The calculation size of the hologram data is 512×512. ... We suppose an eavesdropper attempts to guess the data of the phase key. He begins by testing all possible random binary phase arrays with a small number of pixels, increasing the number of pixels until he succeeds. ...
Optics communications, Jan 1, 2007
We present an image encryption algorithm to simultaneously encrypt two images into a single one a... more We present an image encryption algorithm to simultaneously encrypt two images into a single one as the amplitudes of fractional Fourier transform with different orders. From the encrypted image we can get two original images independently by fractional Fourier transforms with two different fractional orders. This algorithm can be independent of additional random phases as the encryption/ decryption keys. Numerical results are given to analyze the capability of this proposed method. A possible extension to multi-image encryption with a fractional order multiplexing scheme has also been given.
Pattern Analysis and Machine …, Jan 1, 1998
A critical step in automatic ngerprint matching is to automatically and reliably extract minutiae... more A critical step in automatic ngerprint matching is to automatically and reliably extract minutiae from the input ngerprint images. However, the performance of a minutiae extraction algorithm relies heavily on the quality of the input ngerprint images. In order to ensure that the performance of an automatic ngerprint identi cation/veri cation system will be robust with respect to the quality of input ngerprint images, it is essential to incorporate a ngerprint enhancement algorithm in the minutiae extraction module. We present a fast ngerprint enhancement algorithm, which can adaptively improve the clarity of ridge and furrow structures of input ngerprint images based on the estimated local ridge orientation and frequency. We have evaluated the performance of the image enhancement algorithm using the goodness index of the extracted minutiae and the accuracy of an online ngerprint veri cation system. Experimental results show that incorporating the enhancement algorithm improves both the goodness index and the veri cation accuracy.
SIAM Journal on Numerical Analysis, Jan 1, 1990
Abstract. Shock filters for image enhancement are developed. The filters use new nonlinear time d... more Abstract. Shock filters for image enhancement are developed. The filters use new nonlinear time dependent partial differential equations and their discretizations. The evolution of the initial image u0(x, y) as t -- oo into a steady state solution uOO(x, y) through u(x, y, t), t>0, is the filtering ...
Computer graphics and image processing, Jan 1, 1977
A ~mmber of simple and inexpensive enhancement ~echniques are suggosl~ed. These '~echniques attem... more A ~mmber of simple and inexpensive enhancement ~echniques are suggosl~ed. These '~echniques attemp~ to make use of easily computed local contexl, fet~l.ures Ix~ aid in ~he rea,ssignmen~ of each point's gray level during hisi,ogrmn Lransfomutt,ion.
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Papers by Sowmyan Kousthubadharan