Key Generation Algorithms Based on Complex Components of Channel Impulse Response for Massive MIMO Wireless Communication Systems

Physical layer secret key generation is a novel research direction that has attracted many researchers in recent years due to its low computational capacity and ability to obtain information-theoretic security. In this paper, we propose two methods based on the modulus and the real and imaginary parts of the channel impulse response (CIR) matrix to generate a secret key between two legitimate devices in massive Multiple-Input Multiple-Output (MIMO) wireless communication systems. For these methods, the legitimate devices first estimate the channel by using a probing signal to find their CIRs. Next, the CIR matrices are transformed into single-row vectors. The first method uses a simple quantization algorithm to convert the modulus of the complex components of the vector into the final key bit sequence. The second method uses the same quantization algorithm to transform the highest points of the real and imaginary parts into two sequences. The XOR operation between these two sequences generates the final key sequence. The key samples with different lengths generated from the system can be assessed by the most crucial performance metric of randomness according to the National Institute of Standards and Technology (NIST) version 800-22REV1A. The numerical results show that the first method has a higher pass rate and more randomness than the second method. Moreover, our proposed methods are superior to existing methods.