Most simply put, the more gates surrounding an individual's property, the more secure it will be, since we would need to possess the ability to successfully pass more than a single test to proceed. The same applies to any system or solution that makes a decision to proceed based upon the outcome of a test (match or no-match). Adding additional tests produces additional outcomes and additional decisions based upon those outcomes.

Biometric authentication solutions are typically considered unimodal (conducts only a single test) or multimodal (conducts more than a single test):

• Multimodal biometric authentication: This describes an implemented solution that utilizes multiple biometric indicators for identifying the authenticated individuals, such as a photo/image and a signature. A successful match of both biometrics is required to succeed.
• Unimodal biometric authentication: This describes a solution that utilizes only a single level of authentication, such as only a photo/image or a signature. In this case, if the solution matches successfully to the biometric (for example, and image) the attempt is successful.