Multimodal biometric system is the combination of more than one biometric trait to authenticate a person. Unimodal biometric systems use only one biometric trait (voice, gait, signature, iris, retina, face, ear, hand geometry, fingerprint, etc.) to recognize person. Unimodal biometric system have some limitations over authentication like noise in sensed data, intra-class variation, inter-class variations, distinctiveness, spoof attacks etc. Therefore, unimodal biometric system is less secure and less reliable and this is the reason that unimodal biometric systems are become less acceptable where high security required.