Device, system, and method of user authentication utilizing an optical microphone

A system comprising:

• a laser-based self-mix microphone (a) to transmit an outgoing laser signal towards a face of a human speaker, (b) to receive an incoming optical feedback that is reflected back from said face of said human speaker as reflected feedback to said outgoing laser signal, (c) to perform laser self-mix interferometry of said outgoing laser signal and said incoming optical feedback, and (d) based on said laser self-mix interferometry, to generate a user-specific laser self-mix characteristic that uniquely characterizes laser self-mixing of said outgoing laser signal with said incoming optical feedback that is reflected back from said face of said human speaker, wherein said user-specific laser self-mix characteristic uniquely distinguishes between said human speaker and other human speakers;
• a user authentication module to authenticate said human speaker for performing a privileged action, based on said user-specific laser self-mix characteristic that was generated by said laser self-mix interferometry of the outgoing laser signal with said the incoming optical feedback that is associated with said human speaker.