Why Interoperable DIDs Require a Universal ZK Proof Standard

Interoperable DIDs require a universal ZK proof standard. Without it, a credential issued on Ethereum is a siloed data artifact, unusable on Solana or Arbitrum without costly and trust-laden bridging.

Current standards like W3C Verifiable Credentials are insufficient. They define data formats but ignore the execution layer, creating a verifier's dilemma where each chain must run custom, expensive verification logic.

The solution is a canonical proof format, akin to how JPEG standardized images. A DID's proof must be verifiable by any VM, from the EVM to SVM, without custom adapters. This is the ZK interoperability layer missing from today's stack.

Evidence: Projects like Polygon ID and Sismo use circuit-specific proofs, forcing verifiers like Worldcoin or Aave to deploy unique verifiers per chain, a scaling bottleneck that fragments user identity.

Proofs are not portable. A ZK-SNARK proof generated by a Circom circuit on Ethereum is a cryptographic black box to a Halo2 circuit on Polygon. Each proof system uses distinct trusted setups, elliptic curves, and verification keys.

Verification is the bottleneck. A chain like Starknet cannot natively verify a proof from zkSync Era without a custom, expensive verifier smart contract. This creates a fragmented identity landscape where credentials are siloed by their proving stack.

The interoperability tax is real. Projects like Polygon ID and Worldcoin build walled gardens. Bridging a credential requires re-proving off-chain or trusting a relayer, which defeats the purpose of self-sovereign identity.

Evidence: The EIP-7212 standard for secp256r1 verification passed because it defined a single, shared precompile. A universal ZK proof standard is the equivalent precompile for identity, eliminating custom verifier deployment for every new credential type.

Universal proof portability is the core requirement. A DID credential issued on Ethereum must be verifiable on Solana or Polygon without revealing its contents. BBS+ signatures enable a single, compact proof to be generated from any credential, making it the ZK-native credential format for cross-chain identity.

BBS+ outperforms alternatives like CL signatures or SNARKs on a single signature. Unlike CL, BBS+ supports multi-message selective disclosure, letting users prove specific claims (e.g., age > 21) without a trusted setup. Compared to generic SNARKs, BBS+ proofs are orders of magnitude cheaper to verify on-chain.

The W3C Verifiable Credentials standard and projects like Microsoft's Entra Verified ID and the Cheqd network are adopting BBS+. This institutional momentum creates a network effect for interoperability, preventing a fragmented landscape of incompatible DID proof systems.

Without BBS+, interoperability fails. Competing schemes create walled gardens. A user's Polygon-based employment credential becomes useless on Avalanche. BBS+ is the cryptographic primitive that enables the portable, private digital identity layer web3 needs.

Standards create composability, not constraints. A universal ZK proof standard like zk-SNARKs or zk-STARKs provides a common language for verifiable computation. This allows DID systems like Polygon ID or Veramo to focus on application logic, not proof-system plumbing, enabling seamless interoperability across chains from Ethereum to Solana.

Fragmentation is the real innovation killer. Without a standard, every new DID project must build its own proving stack and verification contracts. This wastes engineering resources on recreating the wheel, mirroring the pre-ERC-20 token chaos that stifled DeFi's early growth.

Evidence: The Ethereum Rollup-centric scaling roadmap mandates a standard data availability layer. This constraint didn't stifle innovation; it birthed diverse execution environments like Arbitrum, Optimism, and zkSync that compete on performance, not base-layer compatibility.

Universal ZK standard is mandatory. Without a common proof format, each chain or application like Polygon ID or Worldcoin creates a walled verification garden. This fragmentation defeats the core purpose of a portable, self-sovereign identity.

Proof systems are not interchangeable. A zk-SNARK from zkSync is unintelligible to a zk-STARK prover on Starknet. This incompatibility forces users to re-prove credentials for every new ecosystem, creating prohibitive cost and latency.

The market will consolidate around one dominant format. The current multi-standard landscape mirrors early EVM vs. WASM battles. Network effects and developer adoption, driven by projects like Ethereum's PSE and RISC Zero, will force convergence on a single, efficient verification primitive.

Evidence: The EIP-7212 standard for secp256r1 verification demonstrates how a single cryptographic primitive, once standardized, becomes ubiquitous infrastructure. A similar path is inevitable for the ZK proof that underlies verifiable credentials.