Secret Key Generation from MIMO Channel With or Without Reciprocity

Abstract

This paper presents a generalized channel probing (GCP) method and a generalized pre-processing (GPP) method as two consecutive frontend steps for secret key generation from a MIMO channel between two multi-antenna legitimate nodes against a multi-antenna eavesdropper (Eve). The degree of freedom (DoF) of the secret key capacity (SKC) of GCP/GPP are highlighted and discussed. If the number of antennas on Eve is larger than or equal to the larger number of the antennas on the two legitimate nodes, the SKC-DoF of GCP/GPP within each coherence period equals its minimum, which is either zero for non-reciprocal channel or the product of the numbers of antennas on the two legitimate nodes for reciprocal channel. Otherwise, the SKC-DoF of GCP/GPP increases with the number of random transmissions in GCP within each coherence period regardless of the channel reciprocity. A computational algorithm required for GPP is also discussed, and its performance illustrated via simulations.