Zupass

• Name: Zupass
• URL: https://zupass.org/
• Category: proof wallet / credential-query middleware / proof-carrying-data container
• Summary: Zupass is proof-wallet middleware. The useful layer is the container and query rail between issuers and apps: hold proof-carrying data, answer standardized requests, and stop rebuilding credential handoff every time. Real middleware, not a grand identity stack.
• What it does:
  • Lets users store, organize, and present Proof-Carrying Data such as signatures, Merkle proofs, zk proofs, commitments, and key material
  • Provides a passport-style web app that can answer third-party proof requests and ingest newly issued proofs back into the wallet
  • Exposes interface packages and SDK flows so apps can request proofs through popup or redirect patterns instead of building custom credential-handoff UX
  • Supports many proof families, including ticketing, anonymous group membership, gated access, event attendance, wallet ownership, WebAuthn attestations, and imported offchain account data
  • Uses package families such as @pcd/semaphore-group-pcd, @pcd/webauthn-pcd, and @pcd/ethereum-ownership-pcd, which makes it an aggregation layer over multiple proof types rather than one issuer scheme
  • Includes server-side components for email confirmation, encrypted backups, participant management, and large-asset handling
• Key claims:
  • The real primitive is PCD itself: a claim plus a proof behind a common interface. That is the layer worth keeping.
  • Zupass matters because it standardizes the app-to-proof-wallet handshake. Portability lives partly in that request flow, not just in the underlying circuits.
  • The package spread makes the role clear: this is a container and transport layer over several proof families, not a singular identity issuer.
  • The server docs matter because the system is not pure local-wallet software. Backup, account operations, and hosted query handling create a real middleware dependency.
  • Keep the note small and blunt. Zupass is useful because it removes repeated proof-wallet plumbing, not because it solves identity in the abstract.
• Whitepaper: No canonical standalone Zupass whitepaper or litepaper surfaced in this pass. The strongest primary materials were the official PCD SDK docs, Zupass repository README, interface-package README, and developer resources; see ../whitepapers/zupass-primary-sources-2026-05-10.md.
• Sources:
  • https://zupass.org/
  • https://docs.pcd.team/index
  • https://raw.githubusercontent.com/proofcarryingdata/zupass/main/README.md
  • https://raw.githubusercontent.com/proofcarryingdata/zupass/main/packages/lib/passport-interface/README.md
  • https://raw.githubusercontent.com/proofcarryingdata/zupass/main/packages/lib/pcd-types/README.md
  • https://github.com/proofcarryingdata/zupass
  • https://hackmd.io/@gubsheep/rk4hFy7Gn

Internal linkages

• Keep the cut simple: Zupass is the proof-wallet layer between credential issuance and app verification.
• Best upward reads: world-id, human-passport, and self-protocol.

Control surface

• The leverage sits in hosted query handling, backup and recovery flow, package defaults, and which proof types the surrounding ecosystem standardizes on.

• So treat Zupass as proof-wallet middleware with a real server and interface layer, not as pure local cryptography.

• Last reviewed: 2026-06-15 UTC