Contents I. Introduction
Physical layer security (PLS) has received a lot of interest in recent years. It exploits the randomness of the wireless medium for securing communication, eliminating the need to use cryptographic solutions which are computationally expensive [1]. This renders PLS a potential candidate for securing future communication systems. These systems need to support different traffic types, including those consisting of shorter packets like industrial Internet of Things (IoT) messages, and haptic communications packets, among others, that demand low latency and increased reliability. In practical wireless communication systems, the communication is subject to overhearing by external eavesdroppers due to the broadcast nature of wireless communications. Particularly, the use of short packets introduces a penalty on the secrecy capacity because it is well-known that PLS is based on the assumption that transmission happens with a maximum rate reliably and securely when the blocklengths are sufficiently large. Therefore, the communication links that transmit short packets may become more prone to security attacks. Apart from that, in applications like IoT, there are typically a massive number of connected devices and users. Due to the large-scale nature of the 5G systems, they may be less robust to adversaries. On the other hand, short packet communications result in new challenges in terms of security. Although existing works on PLS have extensively investigated several communication scenarios for wiretap channels, there are only a few studies that focus on PLS for short packet communications. Further, the existing works are limited as they mainly assume a single eavesdropper. Motivated by the above, in this paper, we conduct a short packet analysis of PLS for multiple eavesdroppers and multiple-antenna transmitter settings.
