**2. Soft biometrics**

Soft biometrics provide ancillary information but are not fully distinctive and permanent, so these features cannot provide a reliable person recognition. However, such ancillary information still can be used as a secondary information to complement the primary biometric traits (face, iris, etc.), and these features can be classified to physique (e.g., color skin, gender, ethnic origin), clothing (e.g., clothes' color), or accessories (e.g., glasses, hat) [11].
