Vulnerability evaluation of speaker verification under voice conversion spoofing:The effect of text constraints

Voice conversion, a technique to change one's voice to sound like that of another, poses a threat to even high performance speaker verification system. Vulnerability of text-independent speaker verification systems under spoofing attack, using statistical voice conversion technique, was evaluated and confirmed in our previous work. In this paper, we further extend the study to text-dependent speaker verification systems. In particular, we compare both joint density Gaussian mixture model (JD-GMM) and unit-selection (US) spoofing methods and, for the first time, the performances of text-independent and text-dependent speaker verification systems in a single study. We conduct the experiments using RSR2015 database which is recorded using multiple mobile devices. The experimental results indicate that text-dependent speaker verification system tolerates spoofing attacks better than the text-independent counterpart.