# Post-Quantum Authentication in the MQTT Protocol
## 1 Introduction  
The Internet currently uses different systems to provide secure communication. The transport layer security (TLS) and IP security (IPSec) protocols, along with the public key infrastructure (PKI) framework, are all commonly used communication procedures with security on the Internet. TLS is designed to block attempts to tamper with messages or listen in on what is being communicated [1]. IPSec is used in virtual private networks (VPNs) to authenticate and encrypt messages between two devices [2]. PKI ensures that public keys for devices are available and authenticated by using X.509 digital certificates with digital signatures [3]. Authentication is important, as online communication requires assurance that the communication is occurring between the expected parties and that the exchanged data are not being altered. Standards that can address this issue are the digital signature algorithm (DSA) based on the RSA (Rivest-Shamir-Adleman) cryptosystem or elliptic curves for authentication [4], and the advanced encryption standard (AES) for confidentiality [5]. Quantum computers are a new type of computer that uses qubits rather than bits. This means that the computer is no longer using just 0 or 1, but a superposition of both. Therefore, there are now infinite possible values for each qubit, as it can be any value from 0-1, inclusive. There are quantum algorithms that can be used by quantum computers to break our current security standards. The two main algorithms of note are [PERSON]'s algorithm [6], a quantum algorithm that can be used to find the prime factors of a value; and [PERSON]'s algorithm [7], a quantum algorithm that speeds up the search algorithmfrom \(O(N)\) to \(O(\sqrt{(}N))\). According to [PERSON]'s algorithm, RSA and elliptic curve cryptography (ECC) will be broken [6], and with [PERSON]'s algorithm, AES will need double the key size [8], as we will not be able to rely on current standards for secure Internet communication once quantum computers are available [9]. This makes it necessary for new Internet communication standards to be created to ensure secure communication into the future. Classic computers (computers that rely on classical computing mechanisms for their operation) need new cryptosystems to be considered for Internet communication standards that remain secure against future attacks from quantum computers. These cryptosystems are called postquantum cryptosystems. Physical quantum computers are yet to be commercially available. However, Microsoft has already created a cloud platform that provides quantum tools ([[https://medium.com/swlh/quantum-computing-is-now-publicly-available-df1](https://medium.com/swlh/quantum-computing-is-now-publicly-available-df1) abbc38578]([https://medium.com/swlh/quantum-computing-is-now-publicly-available-df1](https://medium.com/swlh/quantum-computing-is-now-publicly-available-df1) abbc38578) (accessed on 7 February 2023)), Google has a 54-qubit machine called Weber ([[https://quantumai.google/hardware/datasheet/weber.pdf](https://quantumai.google/hardware/datasheet/weber.pdf)]([https://quantumai.google/hardware/datasheet/weber.pdf](https://quantumai.google/hardware/datasheet/weber.pdf)) (accessed on 7 February 2023)) and IBM has a 127-qubit quantum computer called Eagle ([[https://immutabledistribution.com/this-insane-quantum-computer-is-ibms-last-chance/](https://immutabledistribution.com/this-insane-quantum-computer-is-ibms-last-chance/)]([https://immutabledistribution.com/this-insane-quantum-computer-is-ibms-last-chance/](https://immutabledistribution.com/this-insane-quantum-computer-is-ibms-last-chance/)) (accessed on 7 February 2023)). Currently available quantum computers are unable to break current cryptosystems. However, quantum computers have been progressing greatly, and it is projected that they will become available in 20-30 years [10].