Private Revocation (ZK) vs Public Revocation (Transparent)

Privacy-Preserving: No on-chain link between the user and the revoked credential. This matters for financial privacy (e.g., anonymous airdrops) and identity systems (e.g., Iden3, Polygon ID).

Selective Disclosure: Users can prove a credential is valid without revealing its unique identifier, enabling complex attestations.

Computational Overhead: Generating ZK proofs (using Circom, Halo2) adds 2-5 seconds of latency and higher gas costs. This matters for high-frequency DeFi or mobile dApps.

Complex Key Management: Requires secure management of nullifier keys; loss can permanently lock credentials. Increases user onboarding friction.

Low Cost & Fast: Simple on-chain checks (e.g., checking a registry contract) cost < 100k gas and execute in < 1 second. This matters for scalable NFT gating (ERC-721) and high-volume credential checks.

Simple Integration: Easy to audit and integrate with existing standards like EIP-3668 (CCIP Read) or ERC-20 permit-style revocable approvals.

Privacy Leakage: Revocation events publicly link wallet addresses to specific credentials or actions. This matters for corporate compliance or sybil-resistant voting where participant anonymity is required.

Centralized Points of Control: Often relies on a single issuer's registry contract, creating a trust assumption and potential censorship vector.

Privacy-Preserving Proofs: A verifier learns only that a credential is valid and not revoked, without revealing the credential ID or linking to past interactions. This is critical for self-sovereign identity (SSI) and private voting systems where user anonymity must be preserved across sessions.

High Computational & Gas Cost: Generating ZK proofs (e.g., using Circom or Halo2) is computationally intensive for the prover. On-chain verification adds significant gas overhead compared to a simple smart contract check. This matters for high-frequency DeFi or IoT use cases where cost and latency are primary constraints.

Low-Cost & Simple Verification: Revocation status is checked against a public on-chain registry (e.g., an Ethereum smart contract or Solana program). Verification is a simple state lookup, making it ideal for high-throughput applications like NFT gating, loyalty programs, or enterprise credentialing where privacy is not required.

Privacy Leakage & Correlation: Every verification reveals the specific credential ID being checked, allowing verifiers to link all uses of that credential. This creates a privacy vulnerability for applications like anonymous attestations or healthcare credentials, enabling user tracking and profiling.

Zero-knowledge proofs (e.g., Circom, Halo2) enable users to prove a credential is valid without revealing its unique identifier. This prevents tracking of user activity across sessions, a critical requirement for privacy-first DeFi (e.g., Aztec) or anonymous voting systems.

Generating and verifying ZK proofs for revocation (like accumulator non-membership proofs) is computationally intensive. On Ethereum, this can cost >500K gas per verification, making it prohibitive for high-frequency, low-value transactions without L2 scaling.

Revocation status is checked against a public on-chain registry (e.g., an Ethereum smart contract mapping). Verification is a simple SLOAD operation (< 2100 gas), making it ideal for high-throughput applications like NFT-gated access or DAO contributor badges.

Publishing credential identifiers (like Merkle tree indices) on-chain creates permanent, analyzable metadata. This allows third parties to correlate user actions, deanonymize holders, and map social graphs, violating GDPR/CCPA principles for sensitive credentials.