Problems security solution by data transmission in ubiquitous systems based in Rijndael´s algorithm to Wi-fi routers Salvador Gómez Pedraz 1 , Juan Antonio Rodrigo Yanes 2 , José Antonio Gutiérrez de Mesa 3 , Javier de Pedro Carracedo 2 1 Universidad Rey Juan Carlos, Dto. de Informática 28903 Leganés, Spain sgpedraz@inf.uc3m 2 Universidad de Alcalá, Dto. de Automática, 28001 Alcalá de Henares, Spain jrodrigo@aut.uah.es {Bernauer, Wiese}@Springer.de 3 Universidad de Alcalá, Dto. de Ciencias de la Computación, 28001 Alcalá de Henares, Spain jagutierrez@uah.es 1 Introduction At present one of the most important factors that define the managerial evolution is the connectivity give by means of electronic mechanisms, mechanisms that are not exempt from assaults that determine the integrity of the information that is transmitted or the confidentiality of the same one. In our society the availability of the informa- tion is given priority as preponderant factor in real time, therefore it is not only im- portant to have access to the information, but to have access to the correct informa- tion of rapid and sure form. These aspects related to the information and to the sure communication of the same one, make that most of the companies has a direct dependence of the means that allow to interchange information of dynamical form with any part of the world, with- out delays and with the safety of which the interchanged information answers to the beginning of the computer safety: Integrity, Confidentiality, Availability and Don’t- repudiates, as well as the Accessibility. The safety of the wired up nets is by itself complex enough of managing know- ing the spatial limits of our systems. With the wireless nets an extra is going to be added to the above mentioned complexity having to be protected from two important points of view: • The sensitive information in traffic of the users of our system that they choose for the connections Wireless (Privacy and Confidentiality) and • The protection against the attackers' intrusion inside our net (Authentication of connections). To the nets Wireless it is necessary to apply all the possibilities of assault that take are produced in the nets wired up, plus all the possibilities of the nets broadcast and the intrusion of preachers in our systems.