A chain answers only for what arrived Take a plain audit log. Each entry has a sequence number, a payload, and the hash of the previous entry. Entry one has no predecessor. Entry two embeds the hash of entry one, entry three embeds the hash of entry two, and the rest repeat the pattern. A verifier holding entries one through seven can recompute every hash edge. If entry four changed, entry five no longer points at it. If entry three vanished while four through seven remain, the numbering ...