# US 10,770,076 B2 · Magnetic detection of replay attack > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,770,076 B2 - Document ID: US10770076B2 - Status: Granted - Kind: B2 - Application number: 16/020,406 - Filed: 2018-06-27 - Published: 2019-01-03 - Granted: 2020-09-08 - Earliest claimed: 2017-06-28 - Assignees: Cirrus Logic, Inc. - Applicants: Cirrus Logic International Semiconductor Ltd. - Inventors: César Alonso; John Paul Lesso - Web page: https://patentgrep.com/patent/US10770076B2 ## CPC - G10L 17/22: Interactive procedures; Man-machine interfaces - G06F 21/32: using biometric data, e.g. fingerprints, iris scans or voiceprints - G06F 21/554: {involving event detection and direct action} - G10L 17/10: Multimodal systems, i.e. based on the integration of multiple recognition engines or fusion of expert systems - G10L 25/03: characterised by the type of extracted parameters - H04K 1/00: Secret communication - H04K 3/22: {including jamming detection and monitoring} - H04K 3/46: {characterized in that the jamming signal is produced by retransmitting a received signal, after delay or processing} - H04K 3/65: {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} - H04L 9/3231: {Biological data, e.g. fingerprint, voice or retina (network architectures or network communication protocols for supporting authentication of entities using biometrical features in a packet data network H04L63/0861)} - H04L 63/0861: {using biometrical features, e.g. fingerprint, retina-scan (cryptographic mechanisms or cryptographic arrangements for entity authentication using biological data H04L9/3231)} - H04L 63/1466: {Active attacks involving interception, injection, modification, spoofing of data unit addresses, e.g. hijacking, packet injection or TCP sequence number attacks} - H04R 1/406: {microphones} - H04R 3/005: {for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407)} - H04W 12/122: Counter-measures against attacks; Protection against rogue devices - G06F 2221/034: Test or assess a computer or a system - G07C 9/37: using biometric data, e.g. fingerprints, iris scans or voice recognition - G10L 25/78: Detection of presence or absence of voice signals (switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10) - G10L 2021/02166: {Microphone arrays; Beamforming} - H04K 2203/12: for acoustic communication - H04R 2499/13: Acoustic transducers and sound field adaptation in vehicles - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04K: SECRET COMMUNICATION; JAMMING OF COMMUNICATION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - G07C: TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE ## 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 2) 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. ### Claim 4 (depends on 3) 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. ### Claim 5 (depends on 1) 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. ### Claim 6 (depends on 1) 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. ### Claim 7 (depends on 1) A method according to claim 1, wherein said second sample rate is approximately equal to said sample rate. ### Claim 8 (depends on 1) 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. ### Claim 9 (depends on 1) 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. ### Claim 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. ### Claim 11 (depends on 1) A computer program product, comprising a non-transitory computer-readable tangible medium, and instructions for performing a method according to claim 1.