Wiretap Channels With Causal State Information: Strong Secrecy

Te Sun Han,Masahide Sasaki

doi:10.1109/tit.2019.2925611

Abstract

The coding problem for wiretap channels with causal channel state information available at the encoder and/or the decoder is studied under the strong secrecy criterion. This problem consists of two aspects: one is due to naive wiretap channel coding and the other is due to one-time pad cipher based on the secret key agreement between Alice and Bob using the channel state information. These two aspects are closely related to each other and investigated in details from the viewpoint of achievable rates with strong secrecy. The general wiretap channel with various directions of channel state informations among Alice, Bob and Eve (called the multi-way channel state information) is also studied, which includes the above systems as special cases. We provide a unified view about wiretap channel coding with causal multi-way channel state information.

Highlights

I N THIS paper the coding problem for the wiretap channel (WC) with causal channel state information (CSI) available at the encoder (Alice) and/or the decoder (Bob) is studied
Chia and El Gamal [17] addresses the case with causal common CSI available at both Alice and Bob, whereas Fujita [20] deals with the case with causal CSI available only at Alice
The achievability of RCSI-0( p(u), p(x |u, s)) is well known, which is attained by the standard WC coding without resorting to the one-time pad (OTP) cipher using the secret key generated by CSI

Summary

INTRODUCTION

I N THIS paper the coding problem for the wiretap channel (WC) with causal channel state information (CSI) available at the encoder (Alice) and/or the decoder (Bob) is studied. Chia and El Gamal [17] addresses the case with causal common CSI available at both Alice and Bob, whereas Fujita [20] deals with the case with causal CSI available only at Alice (given a physically degraded WC) Both includes lower bounds on the weak secrecy capacity, but with tight secrecy capacity formulas in special cases. We have newly established the “iterative” forward-backward coding scheme for WCs with causal CSI available at Alice with reasonable lower bounds on secrecy capacity.

PROBLEM STATEMENT AND THE RESULT

PROOF OF THEOREM 1

SECRECY CAPACITY RESULTS

COMPARISON WITH THE PREVIOUS RESULT

CONCLUDING REMARKS