The key rotation forger
The hardest case in the register, because it attacks the thing every other page tells you to rely on.
- What they want
- You to replace the fingerprint you pinned with one they control, after which every future check confirms them.
- How they earn
- Everything, permanently. Once the pin is wrong, verification actively works against you.
- What it costs them
- A convincing announcement, and a reason it could not be signed the usual way.
- How you meet them
- A notice that the signing key has rotated, arriving in a place you would expect a notice to arrive.
- What gives them away
- Urgency, and a reason the change cannot be verified normally. A genuine key change never needs you to act inside an hour.
- What stops them
- Waiting several days and looking in places that would have to be compromised separately. Nothing else, because no single message can settle this.
Why this one is genuinely hard
It is self undermining. Anyone able to compromise the old key can sign a handover with it, so a valid signature on a rotation notice proves less than a valid signature normally does. And a real key change does have to happen somehow, so refusing all of them is not a workable policy either.
This is the one place where the confident advice everywhere else on this site runs out, and pretending otherwise would be worse than saying so.
What to do
- Do nothing immediately. Nothing about a key change requires action within an hour, a day, or a week. Any pressure to act sooner is the tell.
- Keep using the old pin. If material still verifies against it, the old key is still in use and the notice is at best premature.
- Wait several days and check independent places. Independent means they would have to be compromised separately, so three pages by one operator count as one.
- Let agreement accumulate. A real change shows up in more than one place, persists, and is reflected wherever the old fingerprint appeared.
- Treat a single source claiming a change as no evidence at all, regardless of how official it looks or how well it explains itself.
The variant that catches people
A notice that does not announce a rotation at all, and simply offers a key alongside something signed by it, with instructions for checking one against the other. Everything is internally consistent because one party produced all three. Internal consistency is free for a forger, which is why a fingerprint has to come from somewhere other than the thing it is verifying. That is the whole reason pinning is a separate step done once.