IMPOSTURE CLASSIFICATION FOR TEXT-DEPENDENT SPEAKER VERIFICATION
Résumé
This work focuses on text-dependent speaker verification, where a user is required to chose and pronounce a customized pass-phrase to get authenticated. In this context, there are three types of impos-tures: an impostor pronouncing the correct pass-phrase, an impostor pronouncing a wrong pass-phrase and the most difficult one: an impostor playing back a recording of the target speaker pronouncing a wrong pass-phrase. Detecting and classifying different types of im-postures can help to prevent future impostures of the same type. In this work, we first propose a new verification score to reject Play-back impostures. This score allows a relative reduction of 90% of the equal error rate against Playback impostures while offering performance similar to the baseline text-dependent score against other types of impostures. As a second contribution, we show that the new score can be combined with an existing text-dependent verification score to improve the classification of the different types of impos-tures. The performance of the speaker verification engine for impos-ture classification is significantly improved with the C llr decreasing by at least 29% compared to the original system.
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