Protecting code integrity with PGP

Linux Foundation Director of IT infrastructure security, Konstantin Ryabitsev, has put together a lengthy guide to using Git and PGP to protect the integrity of source code. In a Google+ post, he called it "beta quality" and asked for help with corrections and fixes. "PGP incorporates a trust delegation mechanism known as the 'Web of Trust.' At its core, this is an attempt to replace the need for centralized Certification Authorities of the HTTPS/TLS world. Instead of various software makers dictating who should be your trusted certifying entity, PGP leaves this responsibility to each user.Unfortunately, very few people understand how the Web of Trust works, and even fewer bother to keep it going. It remains an important aspect of the OpenPGP specification, but recent versions of GnuPG (2.2 and above) have implemented an alternative mechanism called 'Trust on First Use' (TOFU).You can think of TOFU as 'the SSH-like approach to trust.' With SSH, the first time you connect to a remote system, its key fingerprint is recorded and remembered. If the key changes in the future, the SSH client will alert you and refuse to connect, forcing you to make a decision on whether you choose to trust the changed key or not.Similarly, the first time you import someone's PGP key, it is assumed to be trusted. If at any point in the future GnuPG comes across another key with the same identity, both the previously imported key and the new key will be marked as invalid and you will need to manually figure out which one to keep.In this guide, we will be using the TOFU trust model."