# Secret-Key-Aided Scheme for Securing Untrusted DF Relaying Networks

## TL;DR

This paper introduces a secret-key-based security scheme for untrusted relay networks, utilizing buffer-aided key sharing and queueing analysis to enhance secure throughput against untrusted relays.

## Contribution

It proposes a novel secret-key-aided security scheme with buffer management and analyzes its performance in untrusted DF relaying networks.

## Key findings

- Achieves an upper bound on secure throughput.
- Shows significant gains over benchmark schemes.
- Models secret-key buffer as a queueing system.

## Abstract

This paper proposes a new scheme to secure the transmissions in an untrusted decode-and-forward (DF) relaying network. A legitimate source node, Alice, sends her data to a legitimate destination node, Bob, with the aid of an untrusted DF relay node, Charlie. To secure the transmissions from Charlie during relaying time slots, each data codeword is secured using a secret-key codeword that has been previously shared between Alice and Bob during the perfectly secured time slots (i.e., when the channel secrecy rate is positive). The secret-key bits exchanged between Alice and Bob are stored in a finite-length buffer and are used to secure data transmission whenever needed. We model the secret-key buffer as a queueing system and analyze its Markov chain. Our numerical results show the gains of our proposed scheme relative to benchmarks. Moreover, the proposed scheme achieves an upper bound on the secure throughput.