Long-term validity
A proof from 2027. Checked in 2037.
Even if Mandact no longer exists, the original key has expired — or the hash algorithm has been broken. That is the requirement. It decides whether an evidence chain is an archive or merely a log with checksums.
Every entry carries its own algorithm
Not «the chain uses SHA-256», but: this entry was formed with this algorithm. The difference only becomes apparent once an algorithm falls — and by then it is too late to retrofit it. Verification and guard recompute every entry with its own algorithm.
A change is configuration, not a deployment
The permitted algorithms live in a registry with validity periods. If one falls, the next takes over — without anyone touching code. If none is permitted, the write aborts. It does not fall back silently: better an error that is noticed than a proof that lies.
Old entries are not recomputed
That would be the obvious but wrong route — an entry re-hashed after the fact is no longer the same proof. Instead a second anchor is added under the stronger algorithm. Re-anchoring replaces nothing; it lays a blanket over the top.
An anchor set after the break rescues nothing
This is the distinction long-term validity hangs on. A timestamp set after an algorithm was broken attests a hash that was already forgeable at that moment. Only an anchor from the time before it holds. Anyone who does not draw that line is presenting a worthless anchor as a rescue.
The status answer
«Does this proof still hold?» is answered per algorithm epoch, not wholesale. An organisation can hold entries from several epochs — a single answer would be misleading.
- Algorithm still validThe proof holds. No further condition.
- Broken, but anchored beforehandThe proof holds — the anchor attests the state before the break.
- Broken, no earlier anchorThe proof does NOT hold any more. The status says so explicitly instead of concealing it.
Where the trust service comes in
The anchor is the point at which an independent time source is needed. The adapter for it is built — RFC 3161, OASIS DSS over mTLS, and only the hash is transmitted, never the data. It is not in operation: the connection to an accredited service is still outstanding.
Without a configured provider the anchor table stays empty. A simulated timestamp would be worse than none at all.
The trust anchor in detail →What is still open
Re-signing expired signatures, archive-grade evidence packages, and WORM storage are planned but not built. They are listed here because a roadmap that shows only finished things is not one.