Post-quantum cryptography is often described as an algorithm migration: replace today’s cryptography with quantum-safe alternatives and move on. But on the web, the consequences go much deeper. Post-quantum signatures are significantly larger, and simply inserting them into the existing Web PKI challenges the performance and bandwidth assumptions on which TLS and certificate chains were built. PQC does not just change the algorithms: It changes the economics and in consequence the entire architecture.

Merkle Tree Certificates try to maintain the economics by redesigning the handshake. Instead of making every server repeatedly transmit large signatures, they move much of that cost into a public log and let servers prove that their certificate is part of it. This talk explores why post-quantum cryptography forces us to rethink some long-standing assumptions of the Web PKI and how Merkle Tree Certificates work.

Given Merkle Tree Certificates are step by step moving into the pole position to become the new standard, it is important to understand what a transition to this model could mean for the future of TLS and the web.

About the speaker

Benjamin Rothenberger

Principal Security Consultant at Zühlke

Dr. Benjamin Rothenberger is a Principal Security Consultant at Zühlke Engineering AG, specializing in applied cryptography, post-quantum cryptography (PQC), and security architecture. He holds a PhD in Computer Science from ETH Zürich, where his research focused on secure networked systems, cryptographic protocols, and secure Internet architectures such as SCION.
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