Magnetic detection of replay attack

Patent metadata

Field	Value
Publication number	US-10770076-B2
Application number	US-201816020406-A
Country	US
Kind code	B2
Filing date	Jun 27, 2018
Priority date	Jun 28, 2017
Publication date	Sep 8, 2020
Grant date	Sep 8, 2020

Abstract

A method of detecting a replay attack on a voice biometrics system comprises: receiving an audio signal representing speech; detecting a magnetic field; determining if there is a correlation between the audio signal and the magnetic field; and if there is a correlation between the audio signal and the magnetic field, determining that the audio signal may result from a replay attack.

First claim

The invention claimed is:

1. A method of detecting a replay attack on a voice biometrics system, the method comprising:
receiving an audio signal representing speech;
detecting a magnetic field;
determining if there is a correlation between the audio signal and the magnetic field, wherein determining if there is a correlation between the audio signal and the magnetic field comprises:
sampling the detected magnetic field at a first sample rate;
sampling the audio signal at a second sample rate; and
determining if there is a correlation between the sampled audio signal and the sampled detected magnetic field; and

if there is a correlation between the audio signal and the magnetic field, determining that the audio signal may result from a replay attack.

2. A method according to claim 1 , wherein determining if there is a correlation between the audio signal and the magnetic field comprises:
identifying first periods during which the audio signal contains speech;
identifying second periods during which the magnetic field differs from a baseline; and
determining if the first and second periods are substantially the same.

3. A method according to claim 2 , comprising determining that the first and second periods are substantially the same if more than 60% of the first periods during which the audio signal contains speech overlap with the second periods during which the magnetic field differs significantly from a baseline, and/or more than 60% of the second periods during which the magnetic field differs significantly from a baseline overlap with first periods during which the audio signal contains speech.

4. A method according to claim 3 , comprising determining that the first and second periods are substantially the same if more than 80% of the first periods during which the audio signal contains speech overlap with second periods during which the magnetic field differs significantly from a baseline, and/or more than 80% of the second periods during which the magnetic field differs significantly from a baseline overlap with first periods during which the audio signal contains speech.

5. A method according to claim 1 , comprising:
receiving a series of values of a signal representing a magnetic field strength;
forming an average value of the magnetic field strength over a period of time; and
subtracting the average value of the magnetic field strength from the series of values of the signal representing the magnetic field strength to form said detected magnetic field.

6. A method according to claim 1 , comprising:
obtaining a digital audio signal at a third sample rate, and undersampling said digital audio signal to form said audio signal at said second sample rate.

7. A method according to claim 1 , wherein said second sample rate is approximately equal to said sample rate.

8. A method according to claim 1 , wherein the step of determining if there is a correlation between the sampled audio signal and the sampled detected magnetic field comprises performing a mathematical correlation operation on the sampled audio signal and the sampled detected magnetic field to obtain an output correlation function, and determining if a peak value of the output correlation function exceeds a predetermined threshold.

9. A method according to claim 1 , further comprising:
determining a direction of a source of said audio signal representing speech;
determining a direction of a source of said magnetic field; and

determining that the audio signal may result from a replay attack if the direction of the source of said audio signal representing speech corresponds to the direction of the source of said magnetic field.

10. A system for detecting a replay attack on a voice biometrics system, the system comprising:
an input for receiving an audio signal representing speech;
a detector for detecting a magnetic field; and
a processor for:
determining if there is a correlation between the audio signal and the magnetic field, wherein determining if there is a correlation between the audio signal and the magnetic field comprises:
sampling the detected magnetic field at a first sample rate;
sampling the audio signal at a second sample rate; and

determining if there is a correlation between the sampled audio signal and the sampled detected magnetic field; and
if there is a correlation between the audio signal and the magnetic field, determining that the audio signal may result from a replay attack.

11. A computer program product, comprising a non-transitory computer-readable tangible medium, and instructions for performing a method according to claim 1 .

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Alonso César
• Lesso John Paul

Classifications

• H04K3/46

  characterized in that the jamming signal is produced by retransmitting a received signal, after delay or processing · CPC title

• H04K3/65

  using deceptive jamming or spoofing, e.g. transmission of false signals for premature triggering of RCIED, for forced connection or disconnection to/from a network or for generation of dummy target signal · CPC title

• H04K3/22

  including jamming detection and monitoring · CPC title

• H04K1/00

  Secret communication · CPC title

• H04W12/02

  Protecting privacy or anonymity, e.g. protecting personally identifiable information [PII] · CPC title