End-to-end signing and verification is one of the hardest technical and social challenges in open source packaging: it rests at the fault lines of error- and misuse-prone cryptography, long-term secret management, and identity/trust bootstrapping. These challenges have stymied past attempts to do large-scale end-user signing in the Python ecosystem, including PyPI's former (now disabled) support for PGP signature uploads.

Over the past year, PyPI has designed, developed, and deployed a new approach to package signing, one that aims to break the iron triangle of end-user signing: digital attestations, as standardized in PEP 740.

This talk will cover the architectural details of attestations, how attestations were implemented on PyPI and on the client (uploading side), their security properties (including transparency) and advantages, as well as how PyPI was able to enable signing by default for a large swath of the ecosystem without requiring maintainers to change anything about their packaging processes. The talk will also cover the future of attestations, including pieces of the puzzle that are currently missing (like large-scale verification of attestations by parties other than PyPI itself).

The audience is expected to have an intermediate familiarity with Python packaging, including PyPI. No specific familiarity with cryptography is required. Audience members will leave the talk with an improved understanding of the challenges latent in end-user signing, how PEP 740's design and PyPI's implementation overcome those challenges, and how they can both produce and consume attestations today.

Attestations: a new generation of signatures on PyPI - William Woodruff