Secret key establishment between two entities is a fundamental requirement for private communication. The most common method for establishing a secret key is by using public key cryptography. The public key method, however, is vulnerable to security breaches, consumes significant amount of computing resources, has been relatively slow, and requires a third party authentication service.

The proposed method represents a fundamental advancement in secret key exchange for wireless communications by avoiding use of a public key. It allows for the exchange of a random secret key between two transceivers by measuring particular bio-directional properties of the channel, which cannot be read at a third location. The properties may include measurements while moving a transceiver to different locations to observe the secret key. The method takes advantage of the changing space-time wireless channel in order to generate a rich and robust key which can be shared on a wireless link without communicating the secret key.