The main objective of this project was to design, develop and validate a digital signature in a security device for telemedicine applications. Medical domain requires high security conditions for archiving since the information to be protected contains images, diagnosis, personal information of the patients and physicians involved in the telemedicine process. The developed strategy consists in a USB device which allows proper authentication in the information system using a conventional public-private key scheme, through a zero knowledge proof algorithm that guarantees the privacy of the personal password. Once the user is accepted, the device also makes possible the generation of the digital signature required for generated documents.