Let $ℰ/\overline{\mathbb{Q}}$ be an elliptic curve having complex multiplication by a given quadratic order of an imaginary quadratic field $𝕂$. The field of definition of $ℰ$ is the ring class field $\Omega$ of the order. If the prime $p$ splits completely in $\Omega$, then we can reduce $ℰ$ modulo one the factors of $p$ and get a curve $E$ defined over ${𝔽}_p$. The trace of the Frobenius of $E$ is known up to sign and we need a fast way to find this sign, in the context of the Elliptic Curve Primality Proving algorithm (ECPP). For this purpose, we propose...

In [22], the authors proved an explicit formula for the arithmetic intersection number $\left(CM\left(K\right).G_1\right)$ on the Siegel moduli space of abelian surfaces, under some assumptions on the quartic CM field $K$. These intersection numbers allow one to compute the denominators of Igusa class polynomials, which has important applications to the construction of genus $2$ curves for use in cryptography. One of the main tools in the proof was a previous result of the authors [21] generalizing the singular moduli formula of Gross...

The purpose of the present article is the study of duals of functional codes on algebraic surfaces. We give a direct geometrical description of them, using differentials. Even if this description is less trivial, it can be regarded as a natural extension to surfaces of the result asserting that the dual of a functional code $C_L(D,G)$ on a curve is the differential code $C_{\Omega }(D,G)$ . We study the parameters of such codes and state a lower bound for their minimum distance. Using this bound, one can study some examples...

The Legendre symbol has been used to construct sequences with ideal cross-correlation, but it was never used in the arithmetic cross-correlation. In this paper, a new class of generalized Legendre sequences are described and analyzed with respect to their period, distributional, arithmetic cross-correlation and distinctness properties. This analysis gives a new approach to study the connection between the Legendre symbol and the arithmetic cross-correlation. In the end of this paper, possible application...

Joint 2-adic complexity is a new important index of the cryptographic security for multisequences. In this paper, we extend the usual Fourier transform to the case of multisequences and derive an upper bound for the joint 2-adic complexity. Furthermore, for the multisequences with pn-period, we discuss the relation between sequences and their Fourier coefficients. Based on the relation, we determine a lower bound for the number of multisequences with given joint 2-adic complexity.

Joint 2-adic complexity is a new important index of the cryptographic security for multisequences. In this paper, we extend the usual Fourier transform to the case of multisequences and derive an upper bound for the joint 2-adic complexity. Furthermore, for the multisequences with pn-period, we discuss the relation between sequences and their Fourier coefficients. Based on the relation, we determine a lower bound for the number of multisequences...

We consider digit expansions ${\sum }_{j=0}^{\ell -1}{\Phi }^j\left(d_j\right)$ with an endomorphism $\Phi$ of an Abelian group. In such a numeral system, the $w$-NAF condition (each block of $w$ consecutive digits contains at most one nonzero) is shown to minimise the Hamming weight over all expansions with the same digit set if and only if it fulfills the subadditivity condition (the sum of every two expansions of weight $1$ admits an optimal $w$-NAF).This result is then applied to imaginary quadratic bases, which are used for scalar multiplication in elliptic...

Nous montrons dans la première partie l’existence d’un prolongement méromorphe à tout le plan complexe$ℂ$ et explicitons les propriétés et quelques conséquences, d’une large classe de séries zêta des hauteurs associées à l’espace projectif ${\mathbb{P}}_n\left(\mathbb{Q}\right)$$(n\ge 1...$

We connect the discrete logarithm problem over prime fields in the safe prime case to the logarithmic derivative.

We study the functional codes $C_2\left(X\right)$ defined on a projective algebraic variety $X$, in the case where $X\subset {\mathbb{P}}^3\left({𝔽}_q\right)$ is a non-degenerate Hermitian surface. We first give some bounds for $\#X_{Z\left(𝒬\right)}\left({𝔽}_q\right)$, which are better than the ones known. We compute the number of codewords reaching the second weight. We also estimate the third weight, show the geometrical structure of the codewords reaching this third weight and compute their number. The paper ends with a conjecture on the fourth weight and the fifth weight of the code $C_2\left(X\right)$.