Zero Knowledge Payy and Payy Card, the Undoxable Credit Card
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Oct 15, 2025 Sid Gandhi, Co-founder of Payy, and Calum Moore, its technical lead, dive into the future of private payments with the launch of the Payy Card. They discuss using a ZK Validium rollup architecture on Polygon, balancing privacy and compliance, and the intriguing tech behind client-side proofs. The duo reveals how the Payy Card achieves undoxable KYC, ensuring user privacy in transactions. They also explore challenges in self-sovereign finance and share insights on integrating with Visa, paving the way for a user-friendly, privacy-focused payment solution.
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Disconnect KYC From On-Chain Identity
- Design Visa card onboarding so KYC is stored for card issuance but remains unlinkable to on-chain balances.
- Separate Visa transaction records from Payy Merkle state to prevent doxxing.
Card Tap Triggers Fast On‑Chain Escrow Proofs
- During a card tap Payy receives authorization requests and performs on-chain checks within one second to prevent double-spend.
- Payy holds funds in escrow until Visa's later settlement confirms or reverses the charge.
Liability Managed By On‑Chain Escrow And Proofs
- Payy accepts liability to Visa during authorization but mitigates risk by performing on-chain transfers and escrowed holds.
- Clear ZK rules let funds be returned or forwarded depending on Visa settlement results.