I. Introduction
B iometric recognition is the widespread field that models people’s recognition using their physiological or behavioral traits, such as face [1], fingerprint [2], iris [3], voiceprint [4], gait [5], and handwriting [6]. In the last decade, the individual-unique information embedded in bioelectric signals has been gradually mined, and ECG biosignals have been investigated as potential biometric traits [7]. In contrast to external biometric traits, ECG signals have several distinctive characteristics [8]: 1) Liveness detection. ECG signals are recorded by sensors attached to the body, and they can only be captured from a living person. 2) High privacy. ECG signals are difficult to fake at the acquisition stage. 3) Hybrid information. ECG signals contain rich information that can be applied in diverse areas including identity recognition, heart disease monitoring, and emotion analysis. 4) Convenient storage. ECG signals are one-dimensional data that are easy to store and process.