Wyner's work on wiretap channels and the recent works on informationtheoretic security are based on random codes. Achieving information theoreticalsecurity with practical coding schemes is of definite interest. In this note,the attempt is to overcome this elusive task by employing the polar codingtechnique of Ar{\i}kan. It is shown that polar codes achieve non-trivialperfect secrecy rates for binary-input degraded wiretap channels while enjoyingtheir low encoding-decoding complexity. In the special case of symmetric mainand eavesdropper channels, this coding technique achieves the secrecy capacity.Next, fading erasure wiretap channels are considered and a secret key agreementscheme is proposed, which requires only the statistical knowledge of theeavesdropper channel state information (CSI). The enabling factor is thecreation of advantage over Eve, by blindly using the proposed scheme over eachfading block, which is then exploited with privacy amplification techniques togenerate secret keys.
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