In the old days a king would "sign" his proclamations by pressing his "unforgeable" signet into a wax seal. This proved the authenticity of the proclamation.
Normally, the king would declare and sign a proc stating that anything signed by his secretary's "unforgeable" signet was to be respected as well. The secretary could delegate authority to others in turn.
Well turns out that one of the signets in the chain of trust was just a picture of a "four" that anybody could have forged, but nobody noticed because in all of the ceremony and stacks of parchment with wax seals, nobody actually checked if the signet was secure.
The signets were "unforgeable" in that the penalty for copying one was death by being tortured, hanged, drawn and quartered.
They were "unforgeable" because commissioning a jeweler to make an intricate carving on a ring by hand was very expensive in the first place. Finding one who could precisely replicate an existing carving, down to the mistakes of its original author and any wear and tear that would be visible on the wax seal, was almost impossible and even more expensive.
Of course, I didn't mean to imply it took zero effort to copy one, though I guess that's how it read. You'd have to find a skilled jeweler that's also willing to commit treason, so for sure the barrier wasn't insignificant there.
Indeed. In both this scenario and our modern one, we rely on the difficulty of "key material" reproduction being greater than the difficulty of its creation.
That would be retroactive security...
However, Kings likely benefitted from the option of a scapegoat, they could always blame someone for forging their unforgeable seal and have them killed, rather than admit that the seal was true.
If we add in attainder and escheat, the King had a pretty strong hand.
It's enough that the signet could be verified, and sometimes was [1].
As it turns out, these documents were mostly useful for long-lived décisions, which could be overturned, and where a forgery exposed you for a lifetime.
[1]: https://en.wikipedia.org/wiki/Robert_III_of_Artois#The_fraud...
Bravo
"the king has no cryptographically strong certificate"
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