User authentication using variant illumination

One embodiment provides a method, including: providing, using a light source operatively coupled to an information handling device, illumination on an object; capturing, using a sensor operatively coupled to the information handling device, illumination reflectance from the object; determining, using a processor and based on the illumination reflectance, whether the object is associated with a human user and whether the human user is an authorized user; and authenticating, responsive to determining that the object is associated with the human user and that the human user is an authorized user, the human user. Other aspects are described and claimed.