MIMO Authentication via Deliberate Fingerprinting at the Physical Layer

We consider authentication of a wireless multiple-input-multiple-output (MIMO) system by deliberately introducing a stealthy fingerprint at the physical layer. The fingerprint is superimposed onto the data and uniquely conveys an authentication message as a function of the transmitted data and a shared secret key. A symbol synchronous approach to fingerprint embedding provides low complexity operation. In comparison with a conventional tag-based authentication approach, fingerprinting conveys much less information on the secret key to an eavesdropper. We study the trade-offs between stealth, security, and robustness, and show that very good operating points exist. We consider the cases when deterministic or statistical channel state information is available to the transmitter, and show how precoding and channel mode power allocation can be applied to both the data and the fingerprint in combination to enhance the authentication process.