17 research outputs found
Complexity of the Havas, Majewski, Matthews LLL Hermite Normal Form algorithm
We show that the integers in the HMM LLL HNF algorithm have bit length
O(m.log(m.B)), where m is the number of rows and B is the maximum square length
of a row of the input matrix. This is only a little worse than the estimate
O(m.log(B)) in the LLL algorithm.Comment: 10 page
Genetic Algorithms for the Extended GCD Problem
We present several genetic algorithms for solving the extended greatest common divisor problem. After defining the problem and discussing previous work, we will state our results
Certified lattice reduction
Quadratic form reduction and lattice reduction are fundamental tools in
computational number theory and in computer science, especially in
cryptography. The celebrated Lenstra-Lenstra-Lov\'asz reduction algorithm
(so-called LLL) has been improved in many ways through the past decades and
remains one of the central methods used for reducing integral lattice basis. In
particular, its floating-point variants-where the rational arithmetic required
by Gram-Schmidt orthogonalization is replaced by floating-point arithmetic-are
now the fastest known. However, the systematic study of the reduction theory of
real quadratic forms or, more generally, of real lattices is not widely
represented in the literature. When the problem arises, the lattice is usually
replaced by an integral approximation of (a multiple of) the original lattice,
which is then reduced. While practically useful and proven in some special
cases, this method doesn't offer any guarantee of success in general. In this
work, we present an adaptive-precision version of a generalized LLL algorithm
that covers this case in all generality. In particular, we replace
floating-point arithmetic by Interval Arithmetic to certify the behavior of the
algorithm. We conclude by giving a typical application of the result in
algebraic number theory for the reduction of ideal lattices in number fields.Comment: 23 page
A-Tint: A polymake extension for algorithmic tropical intersection theory
In this paper we study algorithmic aspects of tropical intersection theory.
We analyse how divisors and intersection products on tropical cycles can
actually be computed using polyhedral geometry. The main focus of this paper is
the study of moduli spaces, where the underlying combinatorics of the varieties
involved allow a much more efficient way of computing certain tropical cycles.
The algorithms discussed here have been implemented in an extension for
polymake, a software for polyhedral computations.Comment: 32 pages, 5 figures, 4 tables. Second version: Revised version, to be
published in European Journal of Combinatoric
Linearizing torsion classes in the Picard group of algebraic curves over finite fields
We address the problem of computing in the group of -torsion rational
points of the jacobian variety of algebraic curves over finite fields, with a
view toward computing modular representations.Comment: To appear in Journal of Algebr
Computing a Lattice Basis Revisited
International audienc
An identification system based on the explicit isomorphism problem
We propose a new identification system based on algorithmic problems related to computing
isomorphisms between central simple algebras. We design a statistical zero knowledge protocol
which relies on the hardness of computing isomorphisms between orders in division
algebras which generalizes a protocol by Hartung and Schnorr, which relies on the hardness
of integral equivalence of quadratic forms
Rational approximations, multidimensional continued fractions and lattice reduction
We first survey the current state of the art concerning the dynamical
properties of multidimensional continued fraction algorithms defined
dynamically as piecewise fractional maps and compare them with algorithms based
on lattice reduction. We discuss their convergence properties and the quality
of the rational approximation, and stress the interest for these algorithms to
be obtained by iterating dynamical systems. We then focus on an algorithm based
on the classical Jacobi--Perron algorithm involving the nearest integer part.
We describe its Markov properties and we suggest a possible procedure for
proving the existence of a finite ergodic invariant measure absolutely
continuous with respect to Lebesgue measure.Comment: 30 pages, 4 figure