Unshared Secret Key Cryptography
This work addresses secure communication in wireless networks by introducing a novel physical layer cryptographic scheme that eliminates the need for secret key exchange, offering potential improvements in security for applications like military or financial data transmission.
The paper tackled the problem of secure communication over MIMO wiretap channels by proposing an unshared secret key cryptosystem that redesigns artificial noise as a one-time pad secret key, achieving Shannon's ideal and perfect secrecy without secret key exchange for infinite lattice input alphabets and with arbitrarily small outage for finite constellations.
Current security techniques can be implemented with either secret key exchange or physical layer wiretap codes. In this work, we investigate an alternative solution for MIMO wiretap channels. Inspired by the artificial noise (AN) technique, we propose the unshared secret key (USK) cryptosystem, where the AN is redesigned as a one-time pad secret key aligned within the null space between transmitter and legitimate receiver. The proposed USK cryptosystem is a new physical layer cryptographic scheme, obtained by combining traditional network layer cryptography and physical layer security. Unlike previously studied artificial noise techniques, rather than ensuring non-zero secrecy capacity, the USK is valid for an infinite lattice input alphabet and guarantees Shannon's ideal secrecy and perfect secrecy, without the need of secret key exchange. We then show how ideal secrecy can be obtained for finite lattice constellations with an arbitrarily small outage.