Patent attributes
Techniques are described for performing multi-factor authentication of a user during a service session, based at least partly on a code conveyed using an audio file. A code is generated that corresponds to the user and/or their user device. A playback device that is registered to the user can be used to output a playback of an audio file that encodes the code. The playback of the audio file is conveyed through the service session by the user device and received by a backend server, which analyzes the playback of the audio file to extract the code. The user can be authenticated based at least partly on verifying the code that is extracted from the playback of the audio file, by comparing the extracted code to the code that was generated and sent to the playback device.