A Timeline of Public Key Infrastructure: What Worked, What Failed, and What’s Next

Public Key Infrastructure (PKI) has long secured online communication through certificate authorities, but its centralized model faces scalability, flexibility, and trust challenges. This article explores the evolution of PKI and introduces decentralized alternatives—including SDSI, TOFU, IRMA, and Sovrin—that aim to redefine authentication, digital identity, and trust on the internet.