Development and diffusion of embedded systems, directly connected to communication technologies, move people towards the era of ubiquitous computing. An ubiquitous environment needs of many self- contained authentication sensors, opportunely distributed, for users recognition and their secure access. In this work the study and the implementation of a fingerprints-based embedded biometric system for personal ubiquitous authentication is proposed. The system is a self-contained sensor since it is able to perform fingerprint acquisition and processing for user authentication, to strengthen security: the processor performs the entire elaboration steps on board, so that all critical information (i.e. biometric data and cryptographic keys), are securely managed and stored inside the sensor, without any data leaking out. Sensor has been realized on a FPGA-based platform achieving fast execution time and a good final throughput. Resources used, elaboration times and recognition rates of the sensor are finally reported.