Channel Phase Based Secret Key Generation: Untrusted Relaying or Not?

Document Type : Research Article


1 Iran Telecommunication Research Center (ITRC), Tehran, Iran

2 Faculty of Electrical and Computer Engineering, Qom University of Technology, Qom, Iran

3 Department of Electronic and Telecommunications, Polytechnic University of Turin, Italy.


Compared to conventional cryptography methods, physical layer secret key generation (SKG) is more efficient
and suitable for sixth generation (6G) networks due to features such as lightweight and scalability. In the field of SKG, schemes based on local random generators are used for high rate key generation. One of these schemes is random phase injection, where channel probe signals with random phase are exchanged between communication parties (Alice and Bob). In this research work, an SKG scheme is presented in the presence of an untrusted relay, where the relay cannot extract the secret key. In order to make the scheme operational, for the first time, the channel probe signals are considered discrete random phase based on M-PSK signals and multi-bit quantizer is used in the
reception. In addition, in order to reduce the key error rate, quantization with guard bands (GB) is used for key extraction.
For such a scenario, we derive expressions for key agreement rate, key mismatch rate (KMR), and key discarding rate (KDR) per channel probe. The results show that although increasing the GB decreases the KMR metric, the key sequence length also shortens. In the simulation section, we provide useful engineering insights into determining the GB-limited probing signal power as well as the required coding correction capability.


Main Subjects

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