Zupass

Zupass is a zero-knowledge proof-based identity and credential system developed by 0xPARC for Zuzalu in 2023. It lets users prove membership in a group or possession of a credential without revealing which specific person they are. It began as a way to prove "you are a Zuzalu resident" for access control, polling, and event sign-in, and has since become the primary identity layer across the ZuVillage ecosystem.

Vitalik Buterin described it in Why I Built Zuzalu: "The 0xPARC team created Zupass, an identity system based on zero-knowledge proofs that you could use to prove that you were a resident of Zuzalu without revealing which one."

How It Works

Zupass stores credentials ("PCDs" — Proof-Carrying Data) in a client-side wallet. A credential might be: "ticket to Edge City Lanna," "Ethereum core dev," or "voted in this poll." Using ZK proofs, holders can prove predicates about their credentials — "I hold a valid ticket" or "I voted once" — without revealing the underlying data.

The core primitive is the PCD (Proof-Carrying Data) framework, an abstraction for any object that carries a verifiable claim. Different PCD types wrap different proof systems (RSA ticket signatures, Semaphore group membership, EdDSA signatures, etc.). Applications request specific PCD types; Zupass generates the proof client-side.

Key properties:

• Client-side: private keys and credentials never leave the user's device
• ZK proofs: selective disclosure — prove what's needed, nothing more
• Composable: any app can request any PCD type; Zupass is a general wallet, not app-specific
• Pseudonymous by default: proving group membership does not reveal identity

Usage Across the Ecosystem

Zupass has been deployed at every major ZuVillage since 2023:

• Zuzalu 2023 — resident identification, anonymous polling via Zupoll
• Edge City Esmeralda, Crecimiento, Lanna — event ticketing and access
• ETHChiangmai, Devcon side events — ticket gating, vote proofs
• Zuzalu.city — integrated as the primary identity/credential layer

The Zupass.org app is the user-facing wallet. Zupoll and ZuCast are built on top of it.

Significance

Zupass is one of the few pieces of social technology that emerged from the original Zuzalu experiment, was battle-tested in real use, iterated on user feedback, and propagated across subsequent events. Vitalik cited it as evidence that the "incubating novel technologies within a dedicated community" model actually works.

It is also a proof-of-concept for the broader d/acc thesis: that privacy-preserving identity tools are buildable and usable today, not theoretical. The shift from "you must identify yourself to access this space" to "you must prove a predicate about yourself" is the practical application of programmable cryptography to everyday community coordination.

Technical Resources

• Zupass GitHub — open source
• PCD framework documentation
• 0xPARC on programmable cryptography
• Zupoll — anonymous polling built on Zupass

See Also

• Programmable Cryptography
• Privacy Software
• Zuzalu.city
• Zuzalu