Design published · not yet live · no mainnet deployment
Secure Crypto-Fiat Settlement in Poland
Selling crypto for złoty means convincing someone a bank payment happened. A screenshot can be edited and a support agent's judgement is slow and arbitrary, so PayMoney replaces the judgement call with evidence: a cryptographic proof of the payment, checked by a contract that releases the escrow itself.
Nothing here is running yet. This site documents a design — what the protocol specifies, what it costs, and what it cannot do.
See how a settlement worksWhat Makes a Trade Verifiable Here
Three properties do the work, and each is a structural choice rather than a feature bolted on afterwards.
Evidence, Not Discretion
The fiat leg is confirmed by a TLS Notary proof of the bank session — not a screenshot, not a reviewer. Verification and release are the same event, so there is no window in which a payment is sent but unconfirmed.
A Curve-Free Protocol Layer
Settlement is proven by a post-quantum STARK from the Stwo prover, and the vault's hashing, secret sharing and threshold authority rest on hash functions rather than elliptic curves — so Shor's algorithm has nothing to attack there. The bank attestation is the exception, and the security page names it rather than glossing it.
Nobody Holds Your Funds
Value sits in escrow or in a wallet you control, and the settlement contract holds no administrative authority — the protocol section states exactly what it can do. The same property means nothing can be reversed, which the risks page treats as the risk it is.
Settlement estimator
What the buyer must transfer, and the band it has to land inside for a proof to exist at all. Rates here are illustrative, not a quote — nothing has settled yet, so there is no market rate to show.
- Bank transfer, exactly
- —
- Provable band
- — —
- Settlement fee
- open market
- Escrow releases
- —
Pay under the band and no proof exists. Pay over it and no proof exists either — the money has left your bank and the escrow expires back to the seller. What else can go wrong →
Assets at Launch
One asset, and the reason is structural rather than a matter of priorities.
USDC · live at launch
The one asset the deposit path accepts. A deposit is authorised with a signed permit rather than a standing approval, so the vault pulls exactly what you signed for and nothing else, once.
ETH and USDT · roadmap
Not supported at launch. Adding an asset means a new deployment with its own address — it is not a switch we flip, which is the same immutability that stops anyone draining the contract working against convenience here.
What It Costs
Fees are set by an open market. There is no rate card to quote, and nothing is buried in an exchange rate.
- You bid a fee when you post a trade, and a published reserve is the floor. The auction is first-price: the bid you make is the fee you pay.
- The fee is public — both which asset it is paid in and how much — so the market prices itself against settled evidence rather than against our announcement.
- No spread is layered into the rate. The price you are quoted is the price, which is the claim most exchange pricing cannot make.
Read the Design
How a settlement works
The five stages end to end — escrow, the bank payment, the attestation, verification inside a proof, release — and what each costs in time.
Read more →The vault protocol
Resources and kinds, the invariant that replaces value-summing, native account abstraction, and an immutable three-function contract on Ethereum.
Read more →Risks
Overpayment is not refunded, escrow can be locked by a griefer, the notary is a trusted party, deposits are public, and nothing can be reversed.
Read more →
When No One Holds Your Funds, You Hold the Risk
Removing a middleman removes a point of failure and moves the rest onto you. The short version; the full register softens nothing.
Fiat transfers are final
A confirmed bank transfer is not reversible the way a card payment is, and the amount you send is checked but never refunded — the risks page states what overpaying costs and why nothing returns it.
Escrow expiry is the only remedy
If no valid proof arrives before the window closes, the escrow returns to the seller automatically. There is no dispute process, because there is nobody to arbitrate.
Your keys are your responsibility
Authority is knowledge of a key. Lose it with no guardians configured and access is gone; there is no account to reset.
Frequently Asked Questions
Is PayMoney a custodial exchange?
No. Your asset stays in smart-contract escrow or in a wallet you control for the whole trade. There are no platform-held balances and no private keys to surrender, which also means there is no operator who could return funds you send in error.
What happens if the buyer never sends the fiat payment?
If the buyer does not complete the payment before the trade window expires, no valid TLSN payment proof is generated. The smart contract automatically refunds the escrowed cryptocurrency to the seller without requiring manual intervention or dispute resolution.
How does PayMoney verify payments without screenshots?
PayMoney uses TLS Notary (TLSN) to generate a cryptographic proof that a bank transfer has been completed. This verification method uses selective disclosure, confirming payment without revealing sensitive banking information such as account numbers or full transaction details.
Can a fiat payment be reversed after settlement?
No. Once a transfer between Polish bank accounts is confirmed it is generally treated as final under Polish and EU banking rules — there is no chargeback the way a card payment has one. Review the trade terms before sending, because the protocol cannot reverse a settled fiat leg and neither can we.
Which parts of the design are post-quantum, and which are not?
The vault's protocol layer is curve-free by construction — hashing, circle-STARK proofs from the Stwo prover, and Shamir secret sharing rest on assumptions Shor's algorithm does not break. Two elliptic-curve dependencies remain outside it, and naming them is more useful than an absolute claim would be. The security page names both, says which one sits on the settlement path, and states what replacing it would take.
Trade on evidence, not on trust.
Escrow, a proof of payment, and a contract that releases without asking anyone.
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