On the similarities between generalized rank and Hamming weights and their applications to network coding

Rank weights and generalized rank weights have been proven to characterize error and erasure correction, and information leakage in linear network coding, in the same way as Hamming weights and generalized Hamming weights describe classical error and erasure correction, and information leakage in wire-tap channels of type II and code-based secret sharing. Although many similarities between both cases have been established and proven in the literature, many other known results in the Hamming case, such as bounds or characterizations of weight-preserving maps, have not been translated to the rank case yet, or in some cases have been proven after developing a different machinery. The aim of this paper is to further relate both weights and generalized weights, show that the results and proofs in both cases are usually essentially the same, and see the significance of these similarities in network coding. Some of the new results in the rank case also have new consequences in the Hamming case

ISOMORPHIC SIGNAL ENSEMBLES AND THEIR APPLICATION IN ASYNC-ADDRESS SYSTEMS

The object of consideration is async-address systems using code division of subscribers. The subject of the analysis is quasi-orthogonal ensembles of signals based on code sequences that have normalized characteristics of cross-correlation functions (CCF) and provide reliable separation of subscribers (objects) when exposed to imitation and signal-like interference. The purpose of the analysis is to create a model and methodology for construction a set of the best code sequences ensembles having the ability to quickly change the instance of the set to counter imitation and signal-like interference. The solution is based on algebraic models of code sequences and their CCF representation. The article proposes a comprehensive technique to construct signal ensembles set having normalized characteristics of the CCF. The quality of the primary ensemble of code sequences is ensured by the procedure for calculating the CCF optimized in the number of look over options. Optimization is based on the basic properties of the Galois field, in particular, on the Galois fields’ isomorphism property. It provides a significant reduction in calculations when choosing the primary ensemble of code sequences with the specified properties of the CCF. The very choice of the best (largest in size) code sequences ensemble relies on the solution of one of the classical combinatorics problems – searching for maximal clique on a graph. The construction of signals ensembles set having normalized characteristics of the CCF is ensured by the use of special combinatorial procedures and algorithms based on the multiplicative properties of Galois fields. An analysis of the effectiveness of known and proven procedures searching for maximal clique is also performed in this article. The work results will be useful in the design of infocommunication systems using complex signals with a large base and variable structure to provide protection from signal structure research and the effects of imitation and signal-like interferenc

On the discrete logarithm problem in finite fields of fixed characteristic

For $q$ a prime power, the discrete logarithm problem (DLP) in $\mathbb{F}_{q}$ consists in finding, for any $g \in \mathbb{F}_{q}^{\times}$ and $h \in \langle g \rangle$, an integer $x$ such that $g^x = h$. We present an algorithm for computing discrete logarithms with which we prove that for each prime $p$ there exist infinitely many explicit extension fields $\mathbb{F}_{p^n}$ in which the DLP can be solved in expected quasi-polynomial time. Furthermore, subject to a conjecture on the existence of irreducible polynomials of a certain form, the algorithm solves the DLP in all extensions $\mathbb{F}_{p^n}$ in expected quasi-polynomial time.Comment: 15 pages, 2 figures. To appear in Transactions of the AM

On Index Calculus Algorithms for Subfield Curves

In this paper we further the study of index calculus methods for solving the elliptic curve discrete logarithm problem (ECDLP). We focus on the index calculus for subfield curves, also called Koblitz curves, defined over Fq with ECDLP in Fqn. Instead of accelerating the solution of polynomial systems during index calculus as was predominantly done in previous work, we define factor bases that are invariant under the q-power Frobenius automorphism of the field Fqn, reducing the number of polynomial systems that need to be solved. A reduction by a factor of 1/n is the best one could hope for. We show how to choose factor bases to achieve this, while simultaneously accelerating the linear algebra step of the index calculus method for Koblitz curves by a factor n2. Furthermore, we show how to use the Frobenius endomorphism to improve symmetry breaking for Koblitz curves. We provide constructions of factor bases with the desired properties, and we study their impact on the polynomial system solving costs experimentally.SCOPUS: cp.kinfo:eu-repo/semantics/publishe

Deterministic root finding over finite fields using Graeffe transforms

We design new deterministic algorithms, based on Graeffe transforms, to compute all the roots of a polynomial which splits over a finite field F q . Our algorithms were designed to be particularly efficient in the case when the cardinality q − 1 of the multiplicative group of F q is smooth. Such fields are often used in practice because they support fast discrete Fourier transforms. We also present a new nearly optimal algorithm for computing characteristic polynomials of multiplication endomorphisms in finite field extensions. This algorithm allows for the efficient computation of Graeffe transforms of arbitrary orders

Fast Fourier transform via automorphism groups of rational function fields

The Fast Fourier Transform (FFT) over a finite field $\mathbb{F}_q$ computes evaluations of a given polynomial of degree less than $n$ at a specifically chosen set of $n$ distinct evaluation points in $\mathbb{F}_q$. If $q$ or $q-1$ is a smooth number, then the divide-and-conquer approach leads to the fastest known FFT algorithms. Depending on the type of group that the set of evaluation points forms, these algorithms are classified as multiplicative (Math of Comp. 1965) and additive (FOCS 2014) FFT algorithms. In this work, we provide a unified framework for FFT algorithms that include both multiplicative and additive FFT algorithms as special cases, and beyond: our framework also works when $q+1$ is smooth, while all known results require $q$ or $q-1$ to be smooth. For the new case where $q+1$ is smooth (this new case was not considered before in literature as far as we know), we show that if $n$ is a divisor of $q+1$ that is $B$-smooth for a real $B>0$, then our FFT needs $O(Bn\log n)$ arithmetic operations in $\mathbb{F}_q$. Our unified framework is a natural consequence of introducing the algebraic function fields into the study of FFT