Germany's federal API authorization blueprint uses transparency logs — append-only Merkle tree structures — to make authorization changes cryptographically verifiable without trusting any single operator. The design draws on Certificate Transparency principles, using Google's Trillian/Tessera stack. A key architectural decision keeps personal and organizational data out of the central log, satisfying GDPR while preserving tamper-evident integrity. Alongside the log, the OpenID Shared Signals Framework and Security Event Tokens (RFC 8417) provide real-time cross-organizational security event distribution. The core principle: trust is based on protocols and processes, not institutions — insider threats are assumed and misbehavior is made detectable by design.
