Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2018, Director: Artur Travesa i Grau[en] Security on digital communications is a recurrent issue nowadays due to the amount of sensitive information that is exchanged and the fact that we are getting more and more connected with our surroundings. Throughout this essay, we use Shannon’s theory to pull off a study on security from a mathematical point of view with the aim of finding a method which allows the safe exchange of information along insecure communication channels.