BACKGROUND

This disclosure relates generally to voice-based identity verification in voice-enabled computer systems and in particular to acoustic signatures for voice-enabled computer systems.

Voice-enabled computer systems are becoming increasingly popular. Examples include smart phones with “intelligent” assistants, smart speakers, and other devices that can respond to voice input. Voice-enabled computer systems typically use a microphone to detect user speech and a speaker to play audible responses using a synthetic voice. Some voice-enabled computer systems can process detected speech locally to determine a particular request (or command) from the user, then communicate as appropriate with other devices or computer systems (referred to generally as servers) to process the request and determine a response (which can be an action taken or speech response or both). Other voice-enabled computer systems can forward recorded audio to a “backend” server that processes the speech and determines the request. Still other voice-enabled computer systems use a combination of local (client-based) and backend (server-based) processing to respond to user input.

Voice-enabled computer systems can support a range of user interactions that involve varying degrees of security risk. Some interactions, such as a request for a weather forecast or a request to play music, present little security risk regardless of who makes the request. Other interactions, such as a request to unlock a door or a request to access a bank account, may present a significant security risk if an unauthorized person makes the request. Accordingly, some voice-enabled devices may use voice-based identity verification techniques to confirm that a request is being made by an authorized person prior to responding to the request. Voice-based identity verification can include comparing audio characteristics of a recorded request to known audio characteristics of the authorized person's voice. For instance, the user may speak a pass phrase that can be compared to a recorded version to assess frequency characteristics, rate of speaking, pronunciation of words, and/or other characteristics.

Voice-based identity verification can be susceptible to “replay” attacks, in which an unauthorized person obtains a recording of the authorized person's voice and plays the recording later in an attempt to fool the voice-enabled computer system. If the recording is of sufficient quality, a voice-based identity verification process may be unable to distinguish the recording from live speech by the authorized person. Preventing or detecting replay attacks may therefore be desirable.

SUMMARY

Embodiments disclosed herein relate to acoustic signatures that can be used in connection with a voice-enabled computer system. In some embodiments, an acoustic signature can be a specific noise pattern (or other sound) that is played while the user is speaking and that is mixed in the acoustic channel with the user's speech. The microphone of the voice-enabled computer system can capture, as recorded audio, a mix of the acoustic signature and the user's voice. The voice-enabled computer system can analyze the recorded audio (locally or at a backend server) to verify that the expected acoustic signature is present and/or that no previous acoustic signature is present.

Some embodiments of the invention relate to a method performed by a voice-enabled computer system. A method can comprise obtaining a current nonce and operating a speaker of the voice-enabled computer system to produce a current acoustic signature based on the current nonce. The method can further comprise operating a microphone of the voice-enabled computer system, while producing the current acoustic signature, to record audio that includes the current acoustic signature and a speech input, and validating the recorded audio based at least in part on the current acoustic signature. In the event that the recorded audio is validated, the method can further comprise: processing the recorded audio to extract the speech input; processing the speech input to determine an action to perform; and performing the action.

Some embodiments of the invention relate to a server computer comprising a processor, a memory, and a computer readable medium coupled to the processor. The computer readable medium can have stored therein code executable by the processor to implement a method comprising: generating a nonce; providing the nonce to a voice-enabled client having a speaker and a microphone and capable of generating an acoustic signature based on the nonce; receiving, from the voice-enabled client, an audio recording; validating the audio recording based at least in part on detecting the acoustic signature in the audio recording; and processing user speech in the audio recording only if the audio recording is validated.

Some embodiments of the invention relate to a voice-enabled computer system comprising a processor, a memory, a speaker operable by the processor, a microphone operable by the processor, and a computer readable medium coupled to the processor. The computer readable medium can have stored therein code executable by the processor to implement a method comprising: obtaining a nonce; operating the speaker to produce an acoustic signature based on the nonce; and while producing the acoustic signature, operating the microphone to record an audio recording that includes the acoustic signature and a speech input.

The following detailed description, together with the accompanying drawings, will provide a better understanding of embodiments of the invention.

