Due to the sensibility of biometric data, security in biometric devices has to be considered. One of the ways to protect privacy is to include a Tamper-proof operating system. This O.S. would not allow direct access to hardware resources of the device, neither to temporary nor permanent data. This O.S. has also to control the different life stages of the device. A set of requirements have been defined that have to be considered when developing such Tamper-proof O.S.Finally an example of the commands to be covered by some devices have been given. Including this kind of O.S. in all biometric devices will improve the security of the whole system. Unfortunately, when some parts of the biometric system has to be implemented in a general purpose computer with an open Operating System, applying these rules is not easy
