Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2018, Director: Xavier Guitart Morales[en] In this project we study elliptic curve cryptography, which uses groups of points of elliptic curves over finite fields, and Schoof’s algorithm for computing the cardinality of such groups. We introduce the mathematical concepts related to elliptic curves and their group of points, and we describe some elliptic curve based public key cryptosystems. In addition, we provide the necessary background for Schoof’s algorithm, which we describe and implement using the software Sage. We also discuss some criteria used in practice to choose suitable elliptic curves for cryptography, which show the importance of counting points algorithms in cryptographic applications.