Signatures
Four things in this room. Between them they answer the only question in this subject that has a real answer, which is whether the thing in front of you came from the party you think it did.
What is in this room
- A signed blockTwo armour lines, a body, and a lump of base64.
- A fingerprintForty hex characters, and the only part you have to gather yourself.
- A good signature from the wrong keyThe word good appears, and the correct move is still to leave.
- A signature with an old dateSignatures do not expire, so genuine old ones get shown again.
What a signature proves, exactly
Two things, narrowly and completely. That whoever produced the block held one specific private key, and that the text has not been altered since. It does not prove the signer is honest, that the key is still in the same hands, or that the statement is current. Those limits are not weaknesses. A check that claimed to answer everything would be answering nothing.
The four results, in one table
| What you see | What it means | What to do |
|---|---|---|
| Bad signature | The text was altered or invented | Leave. This one is unambiguous |
| No public key | Signed by a key you do not hold | Get the right key after checking its fingerprint, never the one offered on the page |
| Good signature, unexpected key | The maths works, against somebody else key | Leave. The word good is right there, which is why this catches people |
| Good signature, old date | It verifies, and the statement is months old | Treat as unconfirmed. Signatures never expire, so genuine old ones get shown again |
The bottom two rows have their own pages, because they are the two that people report as a pass.
The only thing here that settles anything
A signature is the only claim in this whole subject that can be settled instead of argued about, and it costs about a minute once you have done the hour of work behind it.
The hour that makes the minute worth anything
Everything in this room runs on a fingerprint you collected yourself, and collecting it properly is the only part of this subject that takes real work. Once. About an hour, gathering the same value from places that would have to be broken into separately, comparing them in full, and writing the result down somewhere outside the browser.
After that every check costs under a minute and produces an answer that does not depend on your mood, your experience or how the page looked. People skip the hour and then do the minute against a key from the page they are checking, which is the same as not doing it.
What this room cannot reach
- Whether the signer is honest. Authorship is not character. A market can sign an announcement and still be about to disappear.
- Whether your own machine is telling the truth. Every check here runs on it, so a compromised machine returns whatever it likes. That gap has its own specimen.
- Anything after you log in. A signature covers a block of text, not a session.
Those limits are why the other four rooms exist. A check that answered everything would not be a check, it would be a promise.
The order of operations
- Collect the fingerprint on an ordinary day, not during an outage when everybody is in a hurry and sources agree less.
- Write it down with the date. Then a change is a change rather than a feeling.
- Check the block before you type anything. After the login form the decision has already been made.
- Read which key and what date, in that order, before you read the word good.