1. A processor-implemented method for authenticating a user, comprising: generating a phrase; displaying the phrase to the user; after displaying the phrase to the user, collecting audio signal via an audio sensor and a signal comprising electrocardiogram (ECG) signal via a signal sensor for a first duration based on the displayed phrase; determining a respiratory signal based on the signal collected from the signal sensor; identifying, from the collected audio signal, a speech signal between a first time point and a second time point; determining a distribution of rates of changes of the respiratory signal between the first and second time points; determining a speech respiration co-occurrence (SRC) score based on the distribution of rates of changes of the respiratory signal; if the SRC score is equal to or above a predefined threshold, determining whether the user is authenticated based on the ECG signal collected between the first and second time points.