Abhijit Das

Bio: Abhijit Das is an academic researcher from Indian Institute of Technology Kharagpur. The author has contributed to research in topics: Digital watermarking & Watermark. The author has an hindex of 11, co-authored 49 publications receiving 751 citations. Previous affiliations of Abhijit Das include Indian Institute of Technology Kanpur & Indian Institutes of Technology.

Progress in Cryptology - INDOCRYPT 2008

Abstract: Stream Ciphers.- Slid Pairs in Salsa20 and Trivium.- New Directions in Cryptanalysis of Self-Synchronizing Stream Ciphers.- Analysis of RC4 and Proposal of Additional Layers for Better Security Margin.- New Results on the Key Scheduling Algorithm of RC4.- Cryptographic Hash Functions.- Two Attacks on RadioGatun.- Faster Multicollisions.- A New Type of 2-Block Collisions in MD5.- New Collision Attacks against Up to 24-Step SHA-2.- Public-Key Cryptography - I.- Secure Hierarchical Identity Based Encryption Scheme in the Standard Model.- A Fuzzy ID-Based Encryption Efficient When Error Rate Is Low.- Type-Based Proxy Re-encryption and Its Construction.- Toward a Generic Construction of Universally Convertible Undeniable Signatures from Pairing-Based Signatures.- Security Protocols.- Concrete Security for Entity Recognition: The Jane Doe Protocol.- Efficient and Strongly Secure Password-Based Server Aided Key Exchange (Extended Abstract).- Round Efficient Unconditionally Secure Multiparty Computation Protocol.- A New Anonymous Password-Based Authenticated Key Exchange Protocol.- Group Key Management: From a Non-hierarchical to a Hierarchical Structure.- Hardware Attacks.- Scan Based Side Channel Attacks on Stream Ciphers and Their Counter-Measures.- Floating Fault Analysis of Trivium.- Algebraic Methods in Side-Channel Collision Attacks and Practical Collision Detection.- Block Ciphers.- New Related-Key Boomerang Attacks on AES.- New Impossible Differential Attacks on AES.- Reflection Cryptanalysis of Some Ciphers.- A Differential-Linear Attack on 12-Round Serpent.- New AES Software Speed Records.- Public-Key Cryptography - II.- A New Class of Weak Encryption Exponents in RSA.- Two New Efficient CCA-Secure Online Ciphers: MHCBC and MCBC.- Cryptographic Hardware.- Chai-Tea, Cryptographic Hardware Implementations of xTEA.- High Speed Compact Elliptic Curve Cryptoprocessor for FPGA Platforms.- Elliptic Curve Cryptography.- More Discriminants with the Brezing-Weng Method.- Another Approach to Pairing Computation in Edwards Coordinates.- Threshold Cryptography.- A Verifiable Secret Sharing Scheme Based on the Chinese Remainder Theorem.- Secure Threshold Multi Authority Attribute Based Encryption without a Central Authority.

An audio watermarking scheme using singular value decomposition and dither-modulation quantization

Abstract: Quantization index modulation is one of the best methods for performing blind watermarking, due to its simplicity and good rate-distortion-robustness trade-offs. In this paper, a new audio watermarking algorithm based on singular value decomposition and dither-modulation quantization is presented. The watermark is embedded using dither-modulation quantization of the singular values of the blocks of the host audio signal. The watermark can be blindly extracted without the knowledge of the original audio signal. Subjective and objective tests confirm high imperceptibility achieved by the proposed scheme. Moreover, the scheme is quite robust against attacks including additive white Gaussian noise, MP3 compression, resampling, low-pass filtering, requantization, cropping, echo addition and denoising. The watermark data payload of the algorithm is 196 bps. Performance analysis of the proposed scheme shows low error probability rates.

A New Audio Watermarking Scheme Based on Singular Value Decomposition and Quantization

Abstract: In this paper, we propose a new robust and blind audio watermarking algorithm based on singular value decomposition and quantization index modulation. The watermark insertion and extraction methods are based on quantization of the norm of singular values of the blocks. Audio quality evaluation tests show high imperceptibility of the watermark in the audio signal. Simulation results demonstrate that this algorithm is robust against signal-processing and stirmark attacks. The false negative error probability under the proposed scheme is close to zero. Moreover, the proposed algorithm has higher data payload and better performance than the other related audio watermarking schemes available in the literature.

Batch verification of ECDSA signatures

Abstract: In this paper, we study several algorithms for batch verification of ECDSA signatures. The first of these algorithms is based upon the naive idea of taking square roots in the underlying field. We also propose two new and efficient algorithms which replace square-root computations by symbolic manipulations. Experiments carried out on NIST prime curves demonstrate a maximum speedup of above six over individual verification if all the signatures in the batch belong to the same signer, and a maximum speedup of about two if the signatures in the batch belong to different signers, both achieved by a fast variant of our second symbolic-manipulation algorithm. In terms of security, all the studied algorithms are equivalent to standard ECDSA* batch verification. These algorithms are practical only for small (≤8) batch sizes. To the best of our knowledge, this is the first reported study on the batch verification of original ECDSA signatures.

The C programming language

Abstract: This ebook is the first authorized digital version of Kernighan and Ritchie's 1988 classic, The C Programming Language (2nd Ed.). One of the best-selling programming books published in the last fifty years, "K&R" has been called everything from the "bible" to "a landmark in computer science" and it has influenced generations of programmers. Available now for all leading ebook platforms, this concise and beautifully written text is a "must-have" reference for every serious programmers digital library. As modestly described by the authors in the Preface to the First Edition, this "is not an introductory programming manual; it assumes some familiarity with basic programming concepts like variables, assignment statements, loops, and functions. Nonetheless, a novice programmer should be able to read along and pick up the language, although access to a more knowledgeable colleague will help."

A Survey: Digital Image Watermarking Techniques

Abstract: Multimedia security is extremely significant concern for the internet technology because of the ease of the duplication, distribution and manipulation of the multimedia data. The digital watermarking is a field of information hiding which hide the crucial information in the original data for protection illegal duplication and distribution of multimedia data. This paper presents a survey on the existing digital image watermarking techniques. The results of various digital image watermarking techniques have been compared on the basis of outputs. In the digital watermarking the secret information are implanted into the original data for protecting the ownership rights of the multimedia data. The image watermarking techniques may divide on the basis of domain like spatial domain or transform domain or on the basis of wavelets. The spatial domain techniques directly work on the pixels and the frequency domain works on the transform coefficients of the image. This survey elaborates the most important methods of spatial domain and transform domain and focuses the merits and demerits of these techniques.

The software performance of authenticated-encryption modes

Abstract: We study software performance of authenticated-encryption modes CCM, GCM, and OCB. Across a variety of platforms, we find OCB to be substantially faster than either alternative. For example, on an Intel i5 ("Clarkdale") processor, good implementations of CCM, GCM, and OCB encrypt at around 4.2 cpb, 3.7 cpb, and 1.5 cpb, while CTR mode requires about 1.3 cpb. Still we find room for algorithmic improvements to OCB, showing how to trim one blockcipher call (most of the time, assuming a counter-based nonce) and reduce latency. Our findings contrast with those of McGrew and Viega (2004), who claimed similar performance for GCM and OCB.

Trading Accuracy for Simplicity in Decision Trees

Abstract: When communicating concepts, it is often convenient or even necessary to define a concept approximately. A simple, although only approximately accurate concept definition may be more useful than a completely accurate definition which involves a lot of detail. This paper addresses the problem: given a completely accurate, but complex, definition of a concept, simplify the definition, possibly at the expense of accuracy, so that the simplified definition still corresponds to the concept “sufficiently” well. Concepts are represented by decision trees, and the method of simplification is tree pruning. Given a decision tree that accurately specifies a concept, the problem is to find a smallest pruned tree that still represents the concept within some specified accuracy. A pruning algorithm is presented that finds an optimal solution by generating a dense sequence of pruned trees, decreasing in size, such that each tree has the highest accuracy among all the possible pruned trees of the same size. An efficient implementation of the algorithm, based on dynamic programming, is presented and empirically compared with three progressive pruning algorithms using both artificial and real-world data. An interesting empirical finding is that the real-world data generally allow significantly greater simplification at equal loss of accuracy.