US Patent 11751062 Security apparatus and methods for wireless data exchange

A method of authenticating a first device at a second device for two wirelessly communicating devices, the method comprising: determining the distance between the two devices based on a property of a received communication; at each device, determining at least one shared physical layer property of the communication channel between the two devices; and authenticating the first device based on the determined distance between the two devices and the determined physical layer property of the communication channel.