Discrete Mathematics

Looking for an individual with very sufficient discrete mathematics knowledge concerning topics like: Integers and division algorithm, Congruence modulo relation and modular arithmetic,Number theory,Cryptography as an application, Counting techniques and combinatorics, binary relations, function, equivalence relation and partition, ordered structures, a finite collection of elements, natural numbers, like 1, 2, 3, . . . on a number line, a process (algorithm) involving finite number of steps, a network (graph) involving finite number of nodes