In this episode, Anna Rose and Tarun Chitra catch up with Sid Gandhi and Calum Moore from Payy to discuss the Payy private payment system and the newly released Payy credit card. They explore their focus on building a user-friendly privacy focused product, how ZK tooling advancement makes this possible, and a walkthrough into how it works with the Visa remittance system. Sid and Cal explain Payy's design as a ZK Validium rollup on Polygon, using client-side proofs and a Merkle tree to ensure privacy and compliance. The discussion also delves into the history and past challenges of self-sovereign payments; how self-sovereign money goals were overshadowed by speculation, why many new stablecoin projects feel like a step back to traditional finance, and how privacy-focused payments are making a comeback in 2025. Related links:

ZK Whiteboard Sessions is an educational video series produced by ZK Hack. It is focused on the building blocks of zero knowledge technology. Find season 3 of the Whiteboard Sessions as well as previous seasons here.

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Payy and Payy Card, the Undoxable Credit Card

Zero Knowledge

How UTXO, Merkle Tree, and Client Proofs Provide Privacy

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