An authentication device may include a housing and a finger sensor carried by the housing and including first processing circuitry and a finger sensing area coupled thereto. The first processing circuitry may be configured to generate finger image data based upon a finger positioned adjacent the finger sensing area, and generate and store a first template based upon the finger image data. The authentication device may include second processing circuitry carried by the housing and configured to obtain the finger image data from the first processing circuitry. The second processing circuitry may be configured to generate a second template based upon the finger image data. The first processing circuitry may further be configured to obtain the second template from second processing circuitry, and validate the second template against the first template.