Unshared Secret Key Cryptography: Finite Constellation Inputs and Ideal Secrecy Outage
This work addresses the problem of secure communication without secret key exchange for systems where eavesdroppers have more antennas than transmitters, representing an incremental improvement to enhance practicality.
The paper tackled the limitation of requiring infinite constellation inputs in Unshared Secret Key Cryptography by proposing a practical scheme using finite constellation inputs, achieving Shannon's ideal secrecy with an arbitrarily small outage probability for MIMO wiretap channels.
The Unshared Secret Key Cryptography (USK), recently proposed by the authors, guarantees Shannon's ideal secrecy and perfect secrecy for MIMO wiretap channels, without requiring secret key exchange. However, the requirement of infinite constellation inputs limits its applicability to practical systems. In this paper, we propose a practical USK scheme using finite constellation inputs. The new scheme is based on a cooperative jamming technique, and is valid for the case where the eavesdropper has more antennas than the transmitter. We show that Shannon's ideal secrecy can be achieved with an arbitrarily small outage probability.