We present HNBP-CORE, a lightweight per-device, per-session, append-only hash-chained witness log for tamper-evidence on application state. The protocol's design fits in approximately 50 lines of code and uses only SHA-256 and ISO-8601 timestamping primitives. Each record commits to its predecessor via the predecessor's hash, producing a chain whose integrity can be verified locally without consensus, distributed agreement, or any cooperating third party. Unlike the literature's dominant blockchain framing, HNBP-CORE addresses two underserved problems: (1) a single user wishing to detect whether their own device's recorded state has been silently modified by an adversary; and (2) a producer of high-risk AI systems wishing to satisfy automatic-logging and tamper-evidence obligations under the EU Artificial Intelligence Act (Regulation (EU) 2024/1689, Articles 12 and 19). Both use cases share the same underlying primitive: cross-platform byte-identical hash-chained event logs verifiable with no infrastructure beyond a SHA-256 implementation.
AriaLabs Systems LLC (Tue,) studied this question.