Talks
2011 
(abstract missing)
(abstract missing)
DLP: From RSA to ECDLP and HCDLP (in German and English, 26 slides)
We discuss the difficulty of the discrete logarithm problem in various finite fields. We also examine various attacks on ECDLP and focus on the isogeny attack.
2009 
In 2005, Jao, Miller, and Venkatesan proved that the DLP of elliptic curves with the same endomorhism ring is random reducible under the GRH. In this talk, we discuss a possible generalization of this result to hyperelliptic curves of genus 2 (and 3) defined over a finite field and show the difficulties involved. First, we explain the role of the endomorphism rings of the Jacobian and the polarization. Following the work of Jao, Miller and Venkatesan, we construct isogeny graphs for genus 2 curves. Specifically, we discuss the connection between isogenies and ideal classes in the Jacobian of these curves. This project is research in progress and we describe the current status of this research.
We try to extend the result we presented in our last talk for higher genus curves. We give some background on the arithmetic of curves of high genus and discuss the discrete logarithm problem (DLP) in the divisor class group for curves over finite fields with Jacobian varieties having the same ring of endomorphisms. We strict ourselves to the genus 2 case with Jacobian of CM type and we present the work we have done so far. Finally, we explain which phenomena can occur for curves of genus 3.
We consider elliptic curves with the same order over a finite filed and the same endomorphism ring. We ask whether the discrete logarithm problem has the same complexity. We present a result of Jao, Miller and Venkatesan who proved that the answer to our question is positive under Generalised Riemann Hypothesis. Possible generalisations on curves of higher genus will be discussed in a second talk.
We ask whether the discrete logarithm problem (DLP) in the divisor class group has the same complexity for all curves over finite fields with Jacobian varieties having the same ring of endomorphisms. We present a result of Jao, Miller and Venkatesan who proved that the answer to our question is positive for elliptic curves. We try to use the same methods to extend the result to the genus 2 case in the case that the Jacobian is of CM type and we present the work we have done so far. Finally, we explain which phenomena can occur for curves of genus 3.
2008 
We prove the Iwasava’s Theorem, which describes the behaviour of the class number in an extension of a finite field.
[dvi][ps][pdf]
The basics on the arithmetic on quaternion algebras is introduced: (maximal) orders, (principal) ideals, (reduced) norm/discriminant, ideal classes, etc.
[dvi][ps][pdf]
We ask whether the discrete logarithm problem (DLP) has the same difficulty for all curves with the same order over a finite field. We present the result of Jao, Miller and Venkatesan who proved that the answer to our question is positive if you limit ourselves to curves with the same endomorphism ring.
[ps][pdf]
2007 
The Tensor Product Theorem from Flath asserts that if A is the adele ring of a global field F and G is a reductive algebraic group over F, then G(A) decomposes into a «restricted tensor product» of representations of the groups G(F_{υ}). We give a proof of the theorem.
[dvi][ps][pdf]
2006 
We study modular forms and Galois representations over finite and fields and over the complex numbers. We give the proof of an important theorem from Serre and Deligne that in every modular form of weight 1 we can attach a linear representation. This representation is unique up to isomorphism.
[dvi][ps][pdf]
2004 
We study ring class fields of orders in imaginary quadratic fields to determine which primes are of the form x^{2} + ny^{2}, where x, y integers, for arbitrary n. We give certain examples how our result works in practice.
[dvi][ps][pdf]
A central problem in coding theory is that of finding the smallest length for which there exists a linear code of dimension k and minimum distance d, over a filed of q elements. We consider here the problem for quaternary codes (q = 4), solving the problem for k < 5 for all values of d.
[doc][ps][pdf]
2003 
We consider the primality problem, to decide whether a number is prime or composite. In this survey we show that PRIMES is in coNP and in NP. Then we try a probabilistic approach and we show that PRIMES is in coRP and in ZPP. Finally we present one of the most significant results of the last years: that PRIMES is in P.
Last update: Aug 31, 2005
[doc][mdi][pdf]
With the help of Analytic Number Theory we consider the problem of optimizing the bound used in the quadratic sieve to factorise numbers.
[doc][ps][pdf]
Central problem in coding theory is that of constructing optimal codes for a variable (length, dimension, minimum distance), over a field of q elements, while keeping the other two constant. Here we present one version of the problem, with the help of Finite Geometries, and all the known results until now.
Last update: Jan 14, 2004
[doc][ps][pdf]
2002 
Here is a list of the courses I have attended as an undergraduate student in the University of Crete (19972003). The maximum grade is ten (10), the passing grade is five (5) and the scaling is the following: 8.510 excellent, 6.58.49 very good, 56.49 good. The grade point average (GPA) of graduation is computed according to the Ministerial Decree F141/B3/2166 (FEK 308/18687) for all Greek Universities.
Computer Programming 
10

Algebra I 
9

English I 
7.5

English II 
7.5

English III 
7.5

Calculus I 
7.5

Introduction to Set Theory 
7.5

Linear Algebra I 
7

English IV 
6.5

Probability Theory 
6

Introduction to Analysis II 
6

Introduction to Analysis I 
5

Calculus II 
5

Calculus III 
5

Analytical Geometry – Complex Numbers 
5

Physics I 
5

Theory of Recursive Functions 
10

Number Theory 
9

Special Topics: Computation Theory 
9

Mathematics Education 
7

Discrete Mathematics 
5



Topics in Analysis: The Problem Seminar 
9

Ordinary Differential Equations 
7.5

Topics in Algebra: Cryptology 
10

Rings and Modules Theory 
10

Topics in Algebra: Symbolic Computation 
9.5

Topics in Algebra: Applied Algebra 
8.5

Topics in Algebra: Quadratic Number Fields 
8

Linear Algebra II 
7.5

Group Theory 
7.5

Fields Theory 
7.5

Topics in Algebra: Linear Algebra & Modules 
6

Topics in Applied Mathematics: Algorithms and Complexity Theory 
9.5

Topics in Probability and Statistics: Descriptive Statistics 
8

Numerical Analysis 
6.5

Introduction to Pedagogy 
8

School Pedagogy 
8

Supportive and Compensative Education 
6.5

Algebra I (Graduate) 
9

Numerical Analysis (Graduate) 
8

Algebraic Geometry (Graduate) 
7

Coding (Graduate) 
7

Functional Analysis (Graduate) 
6

Onjob training in Education 
8.5

Diploma Thesis 
9

Projects
– Algorithmic implementations of Brauer invariants. Mainly written reports. (September 2005)
– Junior member of FP6 Research and Training Network «Galois Theory and Explicit Methods» (GTEM). Written reports and implementations in Magma and SAGE. (October 2006 to October 2010)– Toolkit for security tests for Elliptic Curve Cryptography, written both in C++ (using NTL) and Magma. Part of Brainpool for EU passport standards. (December 2006)
– Website construction in PHP. Created http://www.tzimakos.gr in PHP. (January 1998 to present)
– AutoWikiBrowser, Wikipedia specialised browser that uses .NET. Developer. Contributions in C# and Visual Basic for plugins (October 2007 to present)
 2 semesters Algebra I
 1 semester Linear Algebra I
 1 semester Introduction to Computing
 1 semester Applied Algebra
 2 semesters Number Theory
 1 semester Rings and Modules Theory
 1 semester Group Theory
 2 semesters Cryptology
 1 semester Symbolic ComputationsDuring my phD I assisted the following courses:
 1 semester Analysis II at the University of DuisburgEssen
 2 semesters Algebra I at the Carl von Ossietzky University of Oldenburg
 1 semester Algorithmic Number Theory at the Carl von Ossietzky University of Oldenburg
citations
DIANA SAVIN and MIRELA ŞTEFĂNESCU: A necessary condition for certain Primes to be written in the form x^q + ry^q, J. Algebra Appl. 10, 435 (2011) cites M. Magioladitis , Primes of the form x^2 + ny^2.
(check also: DIANA SAVIN: About certain prime numbers arXiv:0907.0315v1 [math.NT] 2 Jul 2009)
DIANA SAVIN: Artin symbol of the Kummer fields, CREATIVE MATH. & INF. 16 (2007), 63 – 69 cites Magioladitis M., Primes of the form x^2 + ny^2.