Physical Layer Security

A method and system for physical layer security are disclosed. In one embodiment, a sender may encode a message word using a secrecy-code encoding, an error-propagation encoding, and an error-correction encoding. The sender may then transmit the encoded message word on a data transmission medium. An intended recipient may receive, on its channel on the data transmission medium, a word having errors from the noise on the intended recipient's channel, and may decode the received word using an error-correction decoder, an error-propagation decoder, and a secrecy-code decoder. Assuming that an eavesdropper's channel is noisier than the intended recipient's channel, the system may be tuned to correct all errors on the intended recipient's channel, but leave, on the eavesdropper's channel, errors that will be propagated and amplified into noise. In an alternate embodiment, a sender and an intended recipient may share a secret key and may use the shared secret key, or values generated by the shared secret key, to populate frozen bits in a polar coding scheme. Because the eavesdropper does not know the shared secret, the eavesdropper's application of successive cancellation decoding results in only noise. This embodiment works as long as the eavesdropper has some noise on its channel.