agenix/doc/problem-and-solution.md

Problem and solution

All files in the Nix store are readable by any system user, so it is not a suitable place for including cleartext secrets. Many existing tools (like NixOps deployment.keys) deploy secrets separately from nixos-rebuild, making deployment, caching, and auditing more difficult. Out-of-band secret management is also less reproducible.

agenix solves these issues by using your pre-existing SSH key infrastructure and age to encrypt secrets into the Nix store. Secrets are decrypted using an SSH host private key during NixOS system activation.