Method for detecting an audio adversarial attack with respect to a voice input processed by an automatic speech recognition system, corresponding device, computer program product and computer-readable carrier medium

A detection device for detecting an audio adversarial attack with respect to a voice input processed by an automatic speech recognition system, the detection device being connected to the automatic speech recognition system, wherein the detection device comprises at least one processor configured to:

• obtain an input audio signal associated with the voice input;
• obtain a transcript resulting from the processing, by the automatic speech recognition system, of the input audio signal;
• convert the transcript into a synthesized audio signal associated with a target text-to-speech voice;
• extract, at a sampling time interval, at least one acoustic feature of a same type, respectively from the input audio signal and from the synthesized audio signal, delivering a first sequence of features vectors associated with the input audio signal and a second sequence of features vectors associated with the synthesized audio signal;
• convert the acoustic features of the first sequence of features vectors and the acoustic features of the second sequence of features vectors to corresponding acoustic features associated with a target reference voice, respectively delivering a first sequence of converted features vectors associated with the input audio signal and a second sequence of converted features vectors associated with the synthesized audio signal;
• compute a dynamic time warping distance between the first sequence of converted features vectors and the second sequence of converted features vectors;
• and
• deliver a piece of data representative of a detection of an audio adversarial attack, as a function of a result of a comparison between the dynamic time warping distance and a predetermined threshold.

A non-transitory computer-readable medium comprising a computer program product recorded thereon, the computer program product comprising instructions which, when the program is executed by a processor, cause the processor to carry out the steps of:

• obtaining an input audio signal (IAS) associated with the voice input;
• obtaining a transcript resulting from the processing, by the ASR, of the IAS;
• converting the transcript into a synthesized audio signal (SAS) associated with a target text-to-speech voice;
• extracting, at a sampling time interval, at least one acoustic feature of a same type, respectively from the input audio signal and from the synthesized audio signal, delivering a first sequence of features vectors (sFV1) associated with the input audio signal and a second sequence of features vectors (sFV2) associated with the synthesized audio signal;
• converting the acoustic features of the sFV1 and the acoustic features of the sFV2 to corresponding acoustic features associated with a target reference voice, respectively delivering a first sequence of converted features vectors (sCFV1) associated with the input audio signal and a second sequence of converted features vectors (sCFV2) associated with the synthesized audio signal;
• computing a dynamic time warping distance between the sCFV1 and the sCFV2;
• and
• delivering a piece of data representative of a detection of an audio adversarial attack, as a function of a result of a comparison between the dynamic time warning distance and a predetermined threshold.