A mobile electronic security device may include a biometric sensor to measure a physical characteristic of a user, an interface component to operatively couple the electronic security device with another device, and a control circuit that are assembled as a single portable unit. Other components, such as a battery, a display, and a memory may be included in the security device. The security device authenticates the identity of a user using output data from the biometric sensor and, in some embodiments, using data from an environmental sensor. Once validated, an encrypted authentication certificate may be output to another device. The security device provides a trusted platform that enables a user to verify his or her identity, show proof of presence of the user, control access to data, etc., and may operate in a standalone manner and/or in conjunction with another device.