Analysis of Trust Models in Public Key Infrastructure: A Systematic Literature Review of Interoperability Challenges

Public Key Infrastructure (PKI) guarantees secure communication and authentication in digital contexts. With the expansion of digital ecosystems, the ability of PKI systems to work together smoothly becomes increasingly important, allowing multiple trust models to be compatible. Nevertheless, several significant challenges must be overcome when merging different trust models. The current body of research does not thoroughly examine these difficulties in various PKI trust models. This study aims to conduct a comprehensive assessment and analysis of the difficulties related to PKI interoperability. The focus will be on trust models such as Cross Certification, Bridge CA, Hierarchical, Hybrid, Cross Recognition, and Certificate Trust Lists. This systematic literature review (SLR) uses the PRISMA technique to analyse trust models in PKI interoperability. The review focuses on peer-reviewed studies published between 2000 and 2024, ensuring transparency and rigor. Eligibility criteria included studies using quantitative methodologies and sourced from major academic databases. This systematic review identified critical challenges in the interoperability of PKI trust models, particularly in operational complexity, security, liability, and scalability. Trust models like Cross Certification, Bridge CA, and Hierarchical systems each present unique challenges when integrated into diverse digital ecosystems. Moreover, gaps in the current research suggest the need for more standardised, scalable solutions that can accommodate the growing complexity of digital infrastructures. Future research should focus on developing a universal model for PKI interoperability, with a particular emphasis on large-scale environments such as E-commerce and E-government systems.