Formalizing Sphinx in Lean

Sat, 31 Oct 2026 00:00:00 +0000

Lean Weekly News scooped this post. Their verification section already reports that cryptlib’s Sphinx packets are binary compatible with the Katzenpost Go implementation, hybrid X25519 and ML-KEM-768 KEM Sphinx included, and links to katzenpost/cryptlib, cryptlib.io and the Reservoir package page. What follows is the longer story.

In Lean, a field of a structure type can be a proposition. That one feature changes how a cryptography library can be written.

Formal Methods on Katzenpost

Formalizing Sphinx in Lean