Adaptation of Zerotrees Using Signed Binary Digit Representations for 3D Image Coding

Zerotrees of wavelet coefficients have shown a good adaptability for the compression of three-dimensional images. EZW, the original algorithm using zerotree, shows good performance and was successfully adapted to 3D image compression. This paper focuses on the adaptation of EZW for the compression of hyperspectral images. The subordinate pass is suppressed to remove the necessity to keep the significant pixels in memory. To compensate the loss due to this removal, signed binary digit representations are used to increase the efficiency of zerotrees. Contextual arithmetic coding with very limited contexts is also used. Finally, we show that this simplified version of 3D-EZW performs almost as well as the original one

Fast multi-computations with integer similarity strategy

Abstract. Multi-computations in finite groups, such as multiexponentiations and multi-scalar multiplications, are very important in ElGamallike public key cryptosystems. Algorithms to improve multi-computations can be classified into two main categories: precomputing methods and recoding methods. The first one uses a table to store the precomputed values, and the second one finds a better binary signed-digit (BSD) representation. In this article, we propose a new integer similarity strategy for multi-computations. The proposed strategy can aid with precomputing methods or recoding methods to further improve the performance of multi-computations. Based on the integer similarity strategy, we propose two efficient algorithms to improve the performance for BSD sparse forms. The performance factor can be improved from 1.556 to 1.444 and to 1.407, respectively

Minimal weight expansions in Pisot bases

For applications to cryptography, it is important to represent numbers with a small number of non-zero digits (Hamming weight) or with small absolute sum of digits. The problem of finding representations with minimal weight has been solved for integer bases, e.g. by the non-adjacent form in base~2. In this paper, we consider numeration systems with respect to real bases $\beta$ which are Pisot numbers and prove that the expansions with minimal absolute sum of digits are recognizable by finite automata. When $\beta$ is the Golden Ratio, the Tribonacci number or the smallest Pisot number, we determine expansions with minimal number of digits $\pm1$ and give explicitely the finite automata recognizing all these expansions. The average weight is lower than for the non-adjacent form

Complexity Analysis of a Fast Modular Multiexponentiation Algorithm

Recently, a fast modular multiexponentiation algorithm for computing A^X B^Y (mod N) was proposed. The authors claimed that on average their algorithm only requires to perform 1.306k modular multiplications (MMs), where k is the bit length of the exponents. This claimed performance is significantly better than all other comparable algorithms, where the best known result by other algorithms achieves 1.503k MMs only. In this paper, we give a formal complexity analysis and show the claimed performance is not true. The actual computational complexity of the algorithm should be 1.556k. This means that the best modular multiexponentiation algorithm based on canonical-sighed-digit technique is still not able to overcome the 1.5k barrier

Minimal weight digit set conversions

Copyright © 2004 IEEEWe consider the problem of recoding a number to minimize the number of nonzero digits in its representation, that is, to minimize the weight of the representation. A general sliding window scheme is described that extends minimal binary sliding window conversion to arbitrary radix and to encompass signed digit sets. This new conversion expresses a number of known recoding techniques as special cases. Proof that this scheme achieves minimal weight for a given digit set is provided and results concerning the theoretical average and worst-case weight are derived.Braden Phillips and Neil Burges

Atomicity Improvement for Elliptic Curve Scalar Multiplication

Abstract. In this paper we address the problem of protecting elliptic curve scalar multiplication implementations against side-channel analysis by using the atomicity principle. First of all we reexamine classical assumptions made by scalar multiplication designers and we point out that some of them are not relevant in the context of embedded devices. We then describe the state-of-the-art of atomic scalar multiplication and propose an atomic pattern improvement method. Compared to the most efficient atomic scalar multiplication published so far, our technique shows an average improvement of up to 10.6%

Balanced Non-Adjacent Forms

Integers can be decomposed in multiple ways. The choice of a recoding technique is generally dictated by performance considerations. The usual metric for optimizing the decomposition is the Hamming weight. In this work, we consider a different metric and propose new modified forms (i.e., integer representations using signed digits) that satisfy minimality requirements under the new metric. Specifically, we introduce what we call balanced non-adjacent forms and prove that they feature a minimal Euclidean weight. We also present efficient algorithms to produce these new minimal forms. We analyze their asymptotic and exact distributions. We extend the definition to modular integers and show similar optimality results. The balanced non-adjacent forms find natural applications in fully homomorphic encryption as they optimally reduce the noise variance in LWE-type ciphertexts