A survey on biometric cryptosystems and their applications.

Biometric systems (BSs) have shown prominent results in providing secure authentication protocols and a unique identification ecosystem for various applications. Over the years, plentiful research has been done to enhance the security of BSs. However, traditional BSs pose security & privacy concerns related to biometric templates, and the research community has been exploring cryptographic schemes to solve these issues. Particularly, Biometric Cryptosystems (BCSs) can address these concerns and enhance the protection of the biometric template. However, BCSs have several associated challenges which provide many research opportunities. Therefore, this survey focuses on BCS techniques and the various Cryptography schemes used to control the security & privacy issues of the biometric templates. We further investigate the potential security threats in BCS and report various attack vectors. We also present the performance analysis of different BCS schemes. Additionally, we explore the use of Blockchain technology for BCS to provide a robust system over a decentralized network. Based on the analysis and identified limitations, we explored the Decentralization of BCS, which aims to address the current challenges in BCS. We also report some potential use cases and future directions to use BCS in Web 3.0 applications built on Blockchain. Finally, we provide a summary of the most pressing issues that still need to be addressed in order to provide reliable privacy and robust security solutions for BCS.