# SPCL: A Smart Access Control System That Supports Blockchain
###### Abstract  
The access control system is a critical element in intelligent buildings. In this paper, we present SPCL, an innovative access control system designed to facilitate building entry through the use of mobile phones. Our system aims to provide a secure and convenient solution for building access, capitalizing on the widespread availability and capabilities of mobile devices. Additionally, we propose a lightweight authentication protocol to enhance security. The performance of the protocol is measured for different curves at different frequencies, proving that the protocol is more suitable for door lock systems than the benchmark protocol. In addition, we investigated the security and usability of SPCL. Finally, a comparison of the security of human-lock interfaces for smart locks and blockchain-based payment methods are discussed. access control; protocol; intelligent building; smart lock; blockchain +
Footnote †: These authors contributed equally to this work. a dedicated Android application. In 2007, [PERSON] et al. [16] deployed a demo smartphone-based system in university buildings, aiming to replace existing access control technologies. The authors in [17] proposed an access control system for intelligent buildings in 2016. In 2018, [PERSON] et al. [18] proposed a security protocol between smartphones, smart locks, and cloud servers, and discussed possible security vulnerabilities. In 2021, [PERSON] et al. [19] proposed a smart home door lock system using security protocol in the Internet of Things (IoT) scenario is proposed, which has the problems of unencrypted data transmission and insufficient authentication methods. [PERSON] et al. [20] developed an enhanced access control system for smart locks, using cloud and edge computing to improve authorization, focusing on scalability and performance. Unfortunately, the approach adds complexity in deploying and enforcing policies. In 2023, [PERSON] et al. [21] designed an IoT-enhanced smart door lock using Radio-Frequency Identification (RFID) for secure access, which is affordable, user-friendly, and includes a fire alarm for additional safety, but it's vulnerable to card loss attacks and unauthorized access. [PERSON] et al. [22] proposed a smart disposable door lock system based on invisible touch sensors to prevent the carrying, loss and copying of cards. Traditional smart lock solutions, while offering convenience, often harbor significant security flaws, including susceptibility to cyber-attacks, data breaches, and unauthorized access. These vulnerabilities primarily stem from their reliance on centralized databases and a lack of robust encryption methodologies. Additionally, the opaque nature of transaction and access logs within these systems has raised concerns regarding their trustworthiness and auditability--critical aspects for both residential and commercial applications. In recent years, there have been some blockchain-based solutions in IoT device scenarios [23; 24; 25], but these solutions are difficult to ensure communication security. The integration of blockchain smart contracts with authentication protocol, especially within the context of smart lock systems, signifies a paradigm shift towards more secure, transparent, and efficient operations. This paper presents a smart lock solution that supports blockchain, aimed at addressing the prevalent security gaps and operational inefficiencies inherent in conventional centralized smart lock solutions. Building on the aforementioned studies, we suggest implementing a smartphone-based smart building access control system. It boasts high security and availability, while ensuring efficiency and user privacy. The main contributions of this paper can be outlined as follows:  
1. A novel access control system, named \"Smart-Phone-Controlled-Lock\" (SPCL), integrating smart lock technology with mobile phone-based access, has been designed and developed. A lightweight privacy protection protocol called the \"SPCL protocol\" is proposed and implemented.