# Post-Quantum Authentication in the MQTT Protocol
## 6 Related Work  
There have been several proposals for adding security to the MQTT scheme. It was suggested in [26] that implementing MQTT over TLS may be practical in most cases, as the increased capacity of IoT devices will make the additional overhead no longer a concern. In [27, 28], secure versions of the MQTT protocol were designed using attribute-based encryption (ABE) [29]. In [27], the authors particularly focused on efficiency, meaning the computational power required for their proposal was less than in [28]. In [30], security architectures and procedures were proposed to provide authentication, integrity and confidentiality for MQTT-SN, a version of MQTT designed to run over the User Datagram Protocol (UDP). Similarly, in [31], the authors tried to address the issue of increased bandwidth by proposing to secure MQTT-SN over UDP rather than standard MQTT over TCP. UDP has smaller packet headers than TCP, so implementing security over MQTT-SN results in smaller packet sizes than implementing security on MQTT. However, in both papers, the issue of postquantum attacks was not addressed, as the authors suggested classical cryptography algorithms such as elliptic curve Diffie-Hellman [32], DTLS or LBlock, a lightweight block cipher [33]. In both papers, the authors concluded that the proposed architectures could provide these security outcomes with reasonable sacrifices to performance.  
Postquantum capability has been added to wolfMQTT, a product of wolfSSL. wolfSSL is an open-source secure sockets layer (SSL) option that is lightweight and popular for use by IoT devices ([[https://www.wolfSSL.com/about/](https://www.wolfSSL.com/about/)]([https://www.wolfSSL.com/about/](https://www.wolfSSL.com/about/)) (accessed on 2 February 2023)). wolfMQTT now provides support for CRYSTALS-Kyber and Falcon at security level 1 ([[https://www.wolfSSL.com/wolfmqtt-post-quantum-kyber-falcon/](https://www.wolfSSL.com/wolfmqtt-post-quantum-kyber-falcon/)]([https://www.wolfSSL.com/wolfmqtt-post-quantum-kyber-falcon/](https://www.wolfSSL.com/wolfmqtt-post-quantum-kyber-falcon/)) (accessed on 2 February 2023)).  
In [34], postquantum MQTT is implemented in an IoT environment and compared with classic algorithms. It is unclear at which security level the authors used these algorithms in, but they found that many postquantum cryptographic algorithms had a manageable increase in latency and overhead. In [35], an IoT network is implemented with MQTT, but only KEMs are tested, so this work does not include authentication. The authors found that postquantum cryptosystems performed similarly to their elliptic curve counterparts.  
All the solutions described above provide security through tested methods, meaning that they do not have any known vulnerabilities. However, they have two key problems. Firstly, they increase the computational power and bandwidth required by IoT devices to run the secured protocol. Secondly, MQTT with classic cryptosystems will not be secure against quantum computer attacks once quantum computers become widely available. Also, the work that has been carried out for postquantum MQTT has been limited and has not necessarily taken into account authentication.