Published checkpoints of the audit log

Each file holds, for every organisation's audit log in Chanzo, a commitment to how many events it held and the SHA-256 hash of the last. Only Chanzo, or the organisation given its own log key, can open an entry; the entries are drawn afresh in each file, so they name no organisation and cannot be followed from one file to the next. Chanzo signs the list with its key (on the verify page) and never changes or removes a file: each names the one before it. Download and keep them; a later change to the log would no longer open them.