Append-only log
Datastruktur där entries only-added, never-modified eller deleted. Tamper-evident: any modification detectable via hash-chain. Foundation för audit-logs, blockchain, certificate-transparency, Sigstore Rekor.
Implementation-patterns: Merkle tree (efficient inclusion-proofs), hash-chain (each entry references previous), blockchain (distributed append-only). Use cases: audit-logs där compliance kräver immutability (PCI DSS, HIPAA), supply-chain transparency (in-toto, Sigstore), Certificate Transparency (Google logs all-TLS-certs). Modern verktyg: Trillian (Google open-source append-only-log-engine, used för CT + Sigstore Rekor), Project Nessie för data-versioning. Anti-pattern: "tamper-resistant" log som can-be-rewritten by admin = not append-only.