Signed QR codes

A QR code is just a picture, and pictures can be printed by anyone. That is the whole security problem of QR payments, and Kit Pay's answer is signing: every merchant QR code the system issues carries a cryptographic signature, and the app verifies that signature before it will treat the code as a payment.

What verification checks

• The signature itself — proof the code was issued by Kit Pay for this merchant, not composed by someone with a QR generator.
• Expiry — codes carry their validity window inside the signed payload, and an expired code is refused.
• Revocation — a merchant can revoke a code, and a revoked code stops resolving even though the printed picture still exists.
• The amount, for amount-locked codes — the payment must match what the code was issued for, or it is refused. Amount-locked vs open codes explains the two kinds.

The design fails closed: anything that does not verify — wrong signature, expired, revoked, mismatched — is refused rather than guessed about. A code that scans but will not resolve is the protection working, not a bug to route around.

What signing means at your counter

For a business, the signature defends your identity: a customer who scans your genuine code sees your merchant account's name, and a forged code claiming to be you fails verification. The classic market fraud — a sticker pasted over a shop's real code, redirecting payments — is exactly what signature checks are built against: the pasted code either fails verification or resolves to a different name than the shop the customer is standing in. Which is why the customer's review screen matters: the name shown there is the verified truth about where money is going.