Patent ID: 8744082

Claim:
A method for secure communications by a first user, the method comprising: estimating, by a processor, a channel between the first user and a second user, thereby producing a first channel estimate comprising a first gain estimate and a first phase estimate of the channel; determining, by the processor, first public information, comprising: selecting a set of one or more time instances from which the first user produces the first channel estimate, wherein selecting the set of one or more time instances comprises: determining a first threshold and a second threshold; selecting a set of channel estimates, wherein the set of channel estimates comprises M or more consecutive channel estimates with gain estimates that are all less than the first threshold or all more than the second threshold, where M is a positive integer value; and selecting time instances corresponding to the selected set of channel estimates; and setting an indicator of the selected set of one or more time instances as the first public information; transmitting, by a transmitter, the first public information regarding the first channel estimate to the second user; determining, by the processor, whether to use only the first gain estimate to generate a first block of secret bits, or to use both the first gain estimate and the first phase estimate to generate the first block of secret bits; and generating, by the processor, the first block of secret bits using the first channel estimate, wherein the generating comprises using the first gain estimate without the first phase estimate to generate the first block of secret bits, when the first gain estimate is less than the first threshold, and wherein the generating comprises using the first gain estimate and the first phase estimate to generate the first block of secret bits, when the first gain estimate is more than the second threshold, wherein the first threshold is lower than the second threshold.