dr. Bas Westerbaan

As Eric Rescorla wrote in 2024 You go to war with the algorithms you have, not the ones you wish you had

It seems like a no-brainer to deploy PQ/T hybrid signatures instead of post-quantum signatures on its own.

For a decade now I’ve worked on migrating to PQC.

If quantum computers were such an imminent threat, why haven’t they factored any number larger than 15 yet?

PQC is a fast moving field.

Cloudflare is launching an experiment with Chrome to evaluate fast, scalable, and quantum-ready Merkle Tree Certificates, all without degrading performance or changing WebPKI trust relationships.

We revisit the problem of private SCT auditing given the recent advances in PIR and changes to the certificate transparency ecosystem.

We take another look at the current landscape of post-quantum signature schemes, and share some relevant surprising statistics on the median number of bytes transferred over a connection on the web.

We take measure of where we are in the migration, and what to expect for the coming years.

We propose X-Wing, a concrete, simple and IND-CCA secure PQ/T hybrid KEM based on X25519 and ML-KEM.

We show how to construct a practical post-quantum anonymous credential scheme.

Large post-quantum signatures force us to rethink the WebPKI.

I discuss the impact on the Web of NIST’s choices for post-quantum algorithms.

How much room does TLS have for the big post-quantum signatures?

We proposed chained CmPKE, a Continuous Group Key Agreement and their underlying efficient Post-Quantum Multi-Recipient KEMs based on Kyber, NTRU LPRime, Frodo and SIKE.

Are there nice assumptions on a category such that any such category must be a category of quantum types with quantum programs between them?

We compare performance of PQ KEMTLS against other TLS variants on the drand system.

We suggest a small change to the Dilithium signature scheme that allows reusing computation between aborted attempts for a speed-up in signing time.

We show that any normal SEA splits as the direct sum of a complete Boolean algebra, a convex normal SEA and a so-called almost-convex normal SEA.

We show that there is a consistent choice of square root in a finite field \(\mathbb{F}_{p^k}\) for odd prime \(p \neq 1\) and \(k\neq 0\) if and only if \(k\) is odd.

A non-trivial σ-effectus with normalization has as scalars either {0,1} or [0,1].

It’s known that affine and relevant monads preserve respectively drop and dup equations.

We prove a Representation Theorem for \(\omega\)-complete effect monoids.

The title says it all.

We propose a definition of purity for positive linear maps between Euclidean Jordan Algebras.

A mathematical study of quantum computing, concentrating on two related, but independent topics.

We give a new way to bound the security of QKD using only the diagrammatic behavior of complementary observables and essential uniqueness of purification for quantum channels.

We explicitly construct oracles to solve binary MQ, which is the underlying hard problem of many proposed post-quantum cryptographic schemes.

We generalize Stinespring’s Dilation Theorem to arbitrary completely positive normal maps between von Neumann algebra’s.

We study the sequential product, the operation \(p * q = \sqrt{p} q \sqrt{p}\) on the set of effects of a von Neumann algebra that represents sequential measurement of first \(p\) and then \(q\).

Effectus theory is a new branch of categorical logic that aims to capture the essentials of quantum logic, with probabilistic and Boolean logic as special cases.

A universal property for \( A \mapsto \sqrt{B} A \sqrt{B} \) appears in a chain of adjunctions.

State spaces in probabilistic and quantum computation are convex sets, that is, Eilenberg–Moore algebras of the distribution monad.

The star-algebra \( M_2 \otimes M_2 \) models a pair of qubits.

A Kochen-Specker system has at least 22 vertices.

A simplification and slight extension of Statman’s Hierarchy Theorem.

An investigation of the sequential product on predicates in the framework of Jacobs.

We introduce several notions of effective undecidability and show they are equivalent to previously investigated notions of completeness and creativity.