“…The state-of-the-art methods for biometric recognition based on PPG signals can use algorithmic approaches [2,32,31,35,10], machine learning techniques based on hand-crafted features [37,25,22,24,33,18,19,29,5,23,14,36], or DNNs [13,1,17,26,9]. To the best of our knowledge, all the methods in the literature process PPG signals using features directly extracted from one-dimensional representations of the signals.…”