In the last few decades, biometric technologies have been employed for subject identification and authentication at an increasing rate due to several inherent advantages. Beyond the traditional biometric systems that use single biometric information, the multi-biometric methods appear to be more popular and accuracy promising. Multi-biometric systems, that merge information from two or more biometric traits taken from the same subject, have gained popularity because they can overcome the limitations such as noisy sensor data, non-universality, susceptibility to spoofing attacks, and large...