For the party checking an exhibit

Check it without us, and without an account.

If somebody has handed you an exhibit produced by this system, you do not have to take our word for it, or theirs. An exhibit is checked offline, by whoever holds it, by a program that talks to no service of ours.

That is the design and not a convenience. A check that had to ask us whether the evidence is good would be a check the party being examined controls.

evidence-verify exhibit.json --policy the-court-policy.json

Two files, and why the second one is yours

The exhibit, and a policy — which log, whose key, which witnesses, which reference time.

An exhibit we hand over carries our proposal for that policy, and a policy supplied by the party being examined is worth nothing on its own: every value in it is one you can obtain elsewhere and substitute. That is the point of separating them. Use ours to see what is being claimed; use your own to decide whether it holds.

With no policy there is no verdict. The program will not quietly default to verifying nothing, because a verdict about nothing, presented as a pass, is worse than a refusal.

What it answers

Four answers, and only two of them are about the evidence.

0validthe sealed data and the policy together establish the record.
1invalidsomething did not check out. This is a verdict about the evidence.
2not a verdictthe file could not be read, or the program was invoked wrongly.
3no verdictnothing failed — the reader did not supply enough to decide. A policy that names no reference time and no timestamp authority is a question nobody answered, not evidence that failed.

Neither 2 nor 3 is a verdict about the evidence, and neither may be reported as one. A program that could not tell “this was tampered with” from “this is not a bundle” would turn a missing file into an accusation.

Getting it

The verifier is free, for anyone who needs to check an exhibit. Write to hello@tallwright.com and it is sent — to you, or directly to the other side, whichever is more useful. The exhibit format is specified, and the specification goes with it.

You are not asked for an account, and you are not asked to register. Our licence undertakes exactly that, and it is the undertaking that makes the rest of this page mean anything: a program you can only get by agreeing to our terms is not a program that checks us.

What it does not tell you

That the record is true. It tells you the record is the one that was sealed, when it says it was sealed, countersigned by the parties the policy names — and that it has not been altered since without that being visible. On Cloud we host the log and run the witness, so there that countersignature is not a check on us.

Whether what was recorded was accurate at the moment it happened is a question about the world, and no cryptography answers it. Anyone who tells you otherwise is selling something.