SIViP DOI 10.1007/s11760-013-0593-4 ORIGINAL PAPER Biometric authentication based on PCG and ECG signals: present status and future directions M. Abo-Zahhad · Sabah M. Ahmed · S. N. Abbas Received: 9 April 2013 / Revised: 3 November 2013 / Accepted: 14 November 2013 © Springer-Verlag London 2013 Abstract Due to the great advances in biomedical digital signal processing, new biometric traits have showed notice- able improvements in authentication systems. Recently, the ElectroCardioGram (ECG) and the PhonoCardioGraph (PCG) have been proposed as novel biometrics. This paper aims to review the previous studies related to the usage of the ECG and PCG signals in human recognition. In addi- tion, we discuss briefly the most important techniques and methodologies used by researchers in the preprocessing, fea- ture extraction and classification of the ECG and PCG sig- nals. At the end, we introduce some future considerations that can be applied in this topic such as: the fusion between different techniques previously used, use both ECG and PCG signals in a multimodal biometric authentication system and building a prototype system for real-time authentication. Keywords Review · Biometric authentication · Electro- cardiography signals · Phonocardiography signals 1 Introduction Human recognition is an increasingly important process in our daily lives. Whether we need to use our own equipment or to prove our identity to third parties in order to use ser- vices or gain access to physical places. Traditional authen- tication methods fall into two categories: proving that you know something (i.e., password-based authentication) and proving that you own something (i.e., token-based authen- tication) [1]. These methods connect the identity with an M. Abo-Zahhad (B ) · S. M. Ahmed · S. N. Abbas Department of Electrical and Electronics Engineering, Faculty of Engineering, Assiut University, Assiut, Egypt e-mail: zahhad@yahoo.com alternate and less rich representation, for instance, a pass- word that can be lost, stolen or shared. A solution to these problems comes from biometric authentication systems. Bio- metric authentication is the recognition of a user’s identity based on specific physiological or behavioral features. Physiological biometrics are based on data derived from direct measurements of a part of human body. Here, we list some examples of those biometrics: – Deoxyribonucleic Acid (DNA): DNA is a molecule encod- ing the genetic instructions used in the development and functioning of all known living organisms and many viruses [2]. – Ear recognition: it is based on the distinctive shape of each person’s ears and the structure of the largely cartilaginous projecting portion of the outer ear [3, 4]. – Facial, hand and hand vein infrared thermogram: these biometrics are based on the pattern of heat radiated by the human body that can be captured by an infrared camera [5]. – Fingerprint: it is an impression on a surface formed by the traces or curves on a fingertip, used as a means of identification [6]. – Palm print: a palm print refers to an image acquired of the palm region of the hand. Similar to fingerprint, it also contains traces, texture and marks which can be used when comparing one palm to another [7]. – Retina recognition: retina recognition technology captures and analyzes the patterns of blood vessels on the retina [8]. – Hand and finger geometry: including its shape, size of palm, and lengths and widths of the fingers [9]. – Iris recognition: the iris is the colored region between the pupil and the white of the eye (also known as the sclera). Iris recognition is the process of recognizing a person by analyzing the apparent pattern of his or her iris [10, 11]. 123