Verifiable Data Vendor Integration: Building a Verifiable Data Layer for Web3 Apps

Description: A concrete, up-to-date playbook for decision‑makers to integrate KYC/market/IoT/enterprise data into Web3 apps with cryptographic assurances—using VC 2.0, attestations (EAS/SAS), Chainlink Functions/Data Streams, ZK‑verified compute, and robust revocation and privacy patterns.

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Why a verifiable data layer now

Between May–November 2025, the core web standards for verifiable credentials became production‑ready: W3C elevated Verifiable Credentials Data Model v2.0, Data Integrity 1.0, and Bitstring Status List v1.0 to Recommendations, giving enterprises a stable, interoperable foundation for machine‑verifiable data exchange and privacy‑preserving revocation. Meanwhile, identity and oracle rails matured: ERC‑4361 Sign‑In with Ethereum (SIWE) reached Final status in 2025, Solana launched its native Attestation Service (SAS), and oracle/compute stacks like Chainlink Functions/Data Streams and Space and Time’s Proof of SQL shipped enterprise‑grade capabilities. Together, these let you turn vendor data into programmable trust for onchain products. (w3.org)

What follows is an implementation‑level guide from 7Block Labs on building a verifiable data layer that your legal, security, and product teams can sign off on—and your smart contracts can consume.

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What “verifiable data layer” means (and what it replaces)

A verifiable data layer (VDL) is a set of services, schemas, and smart‑contract interfaces that:

• Pulls data from vendors (KYC/KYB, market data, IoT/ERP, public records).
• Normalizes it into standard credential/attestation formats.
• Applies cryptographic proofs (signatures, ZK proofs, storage proofs).
• Publishes attestations onchain or offchain with auditability and revocation.
• Exposes simple onchain checks like requireKyc(uid) or priceVerified(feedId).

This replaces brittle “trust the API” flows with cryptographically verifiable pipelines aligned to W3C VC 2.0 and blockchain‑native attestations. (w3.org)

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Anchor to standards: what to adopt in 2026 builds

• W3C Verifiable Credentials 2.0 for the data model and vocabulary. Use JSON‑LD contexts and model issuers/holders/verifiers explicitly to avoid format drift. (w3.org)
• VC Data Integrity 1.0 for embedded proofs; start with EdDSA/ECDSA suites. Consider BBS+ for selective disclosure once cryptosuites finalize. (w3.org)
• Bitstring Status List v1.0 for revocation/suspension at scale with privacy and low bandwidth. Default list size: 131,072 entries (16 KB); recommended TTL defaults to 300,000 ms unless set. (w3.org)
• SD‑JWT (RFC 9901) for selective disclosure when you must interoperate with JWT infrastructure. Use Key Binding to ensure holder consent. (rfc-editor.org)
• SIWE (ERC‑4361) to bind off‑chain sessions to wallets; pair with SIWE ReCaps (ERC‑5573) to authorize scoped capabilities for vendors or your backend. (eips.ethereum.org)

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Choosing your attestation rail

• EVM ecosystems: Ethereum Attestation Service (EAS). Onchain or offchain attestations, schema registry, revocation, EIP‑712 signatures; widely deployed on mainnet/L2s. Mainnet contracts: EAS 0xA1207F3B..., SchemaRegistry 0xA7b39296.... (attest.org)
• Solana ecosystems: Solana Attestation Service (SAS). Native, permissionless attestation protocol for KYC, accreditation, access control, and more; launched on mainnet in May 2025. (solana.com)
• Privacy‑preserving group proofs: Sismo Connect for ZK proofs of membership/attributes without doxxing wallets; onchain Solidity libs and offchain server SDKs. (docs.sismo.io)

Pick EAS when you need EVM composability, SAS for Solana‑native UX/perf, and Sismo when selective disclosure matters more than persistent attestations.

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Vendor categories and integration patterns

1) KYC/KYB and regulatory signals

Pattern:

• Vendor verification -> standardized VC 2.0 credential offchain -> onchain attestation that encodes only what’s needed (e.g., “age >= 21”, “KYC level: full”, “accredited: yes”), either directly or via a Merkle root for private fields.
• Maintain revocation via Bitstring Status List or native attestation revocation flags.

Fresh example on Solana: Sumsub’s Reusable Digital Identity (launched March 2025) demonstrated on‑chain identity attestations via SAS; users reuse verified profiles while apps consume verifiable proofs—without re‑KYCing each time. (sumsub.com)

EVM approach: Use EAS “Private Data Attestations” with Merkle roots to avoid publishing PII onchain; store only a 32‑byte root and keep proofs offchain for selective disclosure. (quicknode.com)

Practical details:

• In VC: set credentialStatus to your Bitstring Status List; TTL default 300,000 ms if unspecified. (w3.org)
• In EAS: sign offchain attestations with EIP‑712 using your corporate attester key; publish UID onchain to timestamp issuance. Enable revocation windows and delegated revocation if your compliance team manages lists centrally. (github.com)

2) Market/RWA data and execution

Pattern:

• For low‑latency prices and execution triggers, use Chainlink Data Streams (sub‑second feeds) and verify onchain via Stream Verifier contracts. For arbitrary API calls or enterprise systems, use Chainlink Functions to fetch, compute, and deliver DON‑agreed results, with threshold‑encrypted secrets. (dev.chain.link)

Recent expansions include Early Access on multiple chains and production deployments with leading DeFi protocols; as of 2025, Chainlink extended Data Streams to new networks and instrument types (including U.S. equities/ETFs). Evaluate availability for your target chain and instruments. (dev.chain.link)

3) Enterprise analytics to ZK‑verified results

Pattern:

• Keep raw data in your warehouse; generate ZK proofs that queries were computed correctly over untampered data; verify proofs onchain.
• Space and Time’s Proof of SQL integrates with BigQuery to provide tamper‑proof query results for onchain use—an enterprise‑friendly bridge to verifiable compute. (cloud.google.com)

4) On‑chain history and cross‑chain proofs

Pattern:

• Use storage/light‑client proofs to verify historical L1/L2 state or cross‑chain messages without trusting a centralized relayer.
• Options: Axiom’s proving API for ZK‑verified Ethereum history and custom compute; Herodotus storage proofs for inclusion/computation; ZK light‑client efforts (e.g., Wormhole + Succinct) for trust‑minimized cross‑chain data. (axiom.xyz)

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Reference architecture: a pragmatic verifiable data layer

1. Ingestion adapters

• Implement stateless connectors per vendor (KYC, price APIs, ERP, IoT).
• Normalize to internal DTOs and VC 2.0 schemas where applicable. Include issuer DID and evidence metadata.
• For JWT‑native vendors, wrap with SD‑JWT to enable selective disclosure flows. (rfc-editor.org)

1. Credentialing and attestation service

• VC issuer: signs Data Integrity proofs (EdDSA/ECDSA); publishes Bitstring Status Lists per issuer/credential type with standard sizes. (w3.org)
• Attestation rail:
  • EAS offchain: sign EIP‑712 typed data; store attestation payload in IPFS or vendor store; anchor with onchain UID for timestamping.
  • EAS onchain: write only non‑PII fields or Merkle roots; enable revocation. (github.com)
  • SAS (Solana): issue schema‑bound attestations; clients verify programmatically. (solana.com)

1. Oracle/compute layer

• Chainlink Functions for arbitrary Web2 data fetch + deterministic compute; secrets via threshold encryption; DON consensus before delivery. Pair with Data Streams where instrument latency matters. (docs.chain.link)
• ZK compute: Proof of SQL for warehouse queries; Axiom/Herodotus for on‑chain history proofs. (cloud.google.com)

1. Smart‑contract interfaces

• Provide tiny, composable gates:
  • requireAttestation(schemaUID, attester, recipient, notExpired)
  • requireVCStatus(vcId, statusListUrl)
  • verifyStreamPrice(streamId, minConfidence)
  • verifyZkQuery(queryId, proof, resultHash)

1. Observability and governance

• Log EAS/SAS UIDs, VC IDs, and vendor request hashes.
• Rotate signing keys in HSMs; publish DID docs; keep auditable evidence stores.
• Maintain revocation SLAs and publish status list TTLs per spec. (w3.org)

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EAS example: KYC gate with private fields

Attestation schema (registered once):

• Schema string: bytes32 merkleRoot, uint32 level, uint32 jurisdiction
• Resolver: custom (optional) to enforce value ranges.

Onchain check (Solidity):

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {IEAS, Attestation} from "@ethereum-attestation-service/eas-contracts/IEAS.sol";

contract KycGate {
    IEAS public immutable eas;
    bytes32 public immutable schemaUID; // EAS schema UID

    constructor(address easAddress, bytes32 _schemaUID) {
        eas = IEAS(easAddress);
        schemaUID = _schemaUID;
    }

    function requireKyc(bytes32 attestationUID) public view {
        Attestation memory a = eas.getAttestation(attestationUID);
        require(a.schema == schemaUID, "Wrong schema");
        require(a.recipient == msg.sender, "Not recipient");
        require(a.expirationTime == 0 || a.expirationTime > block.timestamp, "Expired");
        require(a.revocationTime == 0, "Revoked");
        // Optionally decode `a.data` offchain to verify merkleRoot against user-provided proof
    }
}

Notes:

• Use Ethereum mainnet EAS: 0xA1207F3B…; SchemaRegistry: 0xA7b39296…. Pre‑estimate gas; offchain attestations + onchain UID anchoring can reduce onchain payload size. (github.com)

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Solana example: issuing a SAS attestation from a KYC vendor

SAS exposes programmatic primitives for issuers/holders/verifiers. A typical issuer writes:

import {
  deriveAttestationPda, fetchSchema,
  getCreateAttestationInstruction, sendAndConfirmInstructions
} from "@solana/sas-lib"; // example

const [attestationPda] = await deriveAttestationPda({ credential, schema, nonce: userPubkey });
const schemaDef = await fetchSchema(connection, schema);
const expiry = Math.floor(Date.now()/1000) + 180*24*60*60; // 180 days

const ix = await getCreateAttestationInstruction({
  payer, authority: authorizedSigner,
  credential, schema, attestation: attestationPda,
  nonce: userPubkey, expiry,
  data: serializeAttestationData(schemaDef.data, { kyc_level: 2, over21: true })
});

await sendAndConfirmInstructions(connection, payer, [ix], "KYC attestation created");

SAS launched mainnet in May 2025; vendors like Sumsub have publicly demonstrated issuing on‑chain identity attestations via SAS, enabling reusable compliance across apps. (solana.com)

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Selective disclosure options (production‑ready today)

• Minimal disclosure via BBS+ derived proofs: BBS cryptosuites are in Candidate Recommendation; good for pilots, but review cryptosuite maturity for high‑stakes production. (w3.org)
• SD‑JWT (RFC 9901): ship today in JWT ecosystems; use Key Binding (kb+jwt) and holder signatures to prevent replay or coerced disclosure. (rfc-editor.org)
• ZK group proofs (Sismo): verify membership or thresholds without linking wallets. Good for sybil resistance and “over‑18/over‑21” gates. (docs.sismo.io)

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Revocation you can count on

• Use Bitstring Status List v1.0 for VC revocation/suspension: compact, cacheable, privacy‑preserving. Default 131,072 entries per list; ensure HTTP cache headers align with ttl (default 300,000 ms). Maintain separate lists for purposes like revocation vs suspension. (w3.org)
• For attestations, set revocable=true where policy requires; publish revocation UIDs and index them in your explorer/docs. (github.com)

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Oracle and compute: when to use what

• Low‑latency market data and automated execution: Chainlink Data Streams; check your chain’s Early Access status and verifier proxy addresses. Use alongside standard Data Feeds for settlement‑grade redundancy. (dev.chain.link)
• Arbitrary API reads and serverless compute: Chainlink Functions; run code across a DON, aggregate results, deliver onchain; secrets via threshold encryption. Great for “call a private ERP endpoint -> compute -> attest result.” (docs.chain.link)
• Warehouse analytics to smart contracts: Space and Time Proof of SQL for ZK‑verified queries over BigQuery data. (cloud.google.com)
• Historical onchain proofs and cross‑chain trust: Axiom V2 (API beta) and Herodotus storage proofs; follow ZK light‑client progress (e.g., Wormhole + Succinct) for trust‑minimized bridging. (axiom.xyz)

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Security, privacy, and compliance guardrails

• Keys and DIDs: Store VC issuer/attester keys in HSMs; publish DID documents; rotate on schedule with public announcements.
• Data minimization: Only put non‑PII or Merkle roots onchain; never store raw IDs or document numbers on L1. For offchain caches, encrypt at rest and set strict TTLs.
• Consent and scope: Bind sessions with SIWE and authorize scopes with ERC‑5573 ReCaps to ensure relying parties act only as agreed. (eips.ethereum.org)
• Evidence retention: Keep vendor raw responses, canonicalization steps, and hash chains for audit. Store proofs next to UIDs/VC IDs.
• Jurisdiction toggles: Express jurisdiction and sanctions screening level as attested attributes; version schemas when regulations change (e.g., new AML data points).

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Implementation timeline (6–8 weeks to pilot)

• Week 1: Requirements and threat modeling. Choose rails (EAS/SAS/Sismo) and chains; pick VC cryptosuite (Data Integrity EdDSA to start).
• Week 2: Schema design. Draft VC contexts and EAS/SAS schemas for KYC Level, Jurisdiction, Accreditation, AgeOver21, etc., plus Bitstring Status List structure. (w3.org)
• Week 3: Vendor adapters. Integrate a KYC vendor (e.g., Sumsub), normalize to VC 2.0, emit EAS offchain attestations; add revocation handler. (sumsub.com)
• Week 4: Onchain gating. Deploy gates in two dApps (e.g., RWA mint with “Accredited: true”, DeFi pool with “KYC: level >= 2”).
• Week 5: Oracle/compute. Add Chainlink Functions for a proprietary API; add Data Streams if you need low‑latency market data. (docs.chain.link)
• Week 6: ZK optionality. Pilot Sismo group proofs for sybil resistance or Proof of Humanity style checks. (docs.sismo.io)
• Weeks 7–8: Security review and compliance sign‑off. HSM key ops, DID publication, revocation SLAs, and legal annexes.

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KPIs to track

• Time‑to‑verify (TTV): vendor response -> attestation issuance -> onchain verification latency.
• Reuse rate: % of sessions reusing existing credentials (Sumsub ID/SAS or EAS offchain UID). (sumsub.com)
• Revocation freshness: median age of cached status lists vs ttl.
• Onchain gas/compute per check: favor offchain attestations anchored by UIDs when feasible. (quicknode.com)
• Coverage: % of active users with valid attestations across jurisdictions.

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Emerging best practices we recommend

• Standardize everything: VC 2.0 for semantics, Data Integrity for signatures, Bitstring Status Lists for scalable revocation; only drop to custom formats if absolutely necessary. (w3.org)
• Separate evidence from attestations: Attest minimal claims; store evidence hashes and keep raw documents in secure evidence stores.
• Prefer reusable identity flows: SAS on Solana and EAS offchain UIDs reduce repeat KYC friction. (solana.com)
• Use capability‑based access: Bind signed scopes to vendors/backends with SIWE ReCaps; log capability use for audits. (eips.ethereum.org)
• Plan for cryptosuite agility: Keep a migration path to BBS+ or post‑quantum suites; abstract proof verification behind a service boundary. (w3.org)

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Where 7Block Labs plugs in

• Schema and policy design: Align business rules with VC/attestation schemas and legal constraints.
• Vendor integrations: Build adapters for KYC/KYB, ERP, market data; normalize to VC 2.0 and attestations.
• Rail deployment: EAS (EVM), SAS (Solana), Sismo Connect; revocation ops with Bitstring Status Lists.
• Oracle/compute: Chainlink Functions/Data Streams and Proof of SQL hookups to your data warehouse.
• End‑to‑end audits: Evidence chains, DID/key management, and compliance playbooks.

If you’re ready to convert vendor data into programmable trust, we’ll help you ship a verifiable data layer in under two months—with the cryptography, standards alignment, and product ergonomics your users and regulators expect.

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Appendix: quick links and facts we used

• W3C VC DM v2.0, Data Integrity 1.0, Bitstring Status List v1.0 are W3C Recommendations since May 15, 2025. Bitstring lists default to 131,072 entries; ttl defaults to 300,000 ms if unspecified. (w3.org)
• ERC‑4361 (SIWE) finalized in 2025; use ERC‑5573 ReCaps for scoped capabilities. (etherworld.co)
• EAS Ethereum mainnet: EAS 0xA1207F3B…, SchemaRegistry 0xA7b39296…. Offchain attestations use EIP‑712; private data attestations use Merkle roots. (github.com)
• Solana Attestation Service launched on mainnet May 2025; Sumsub demoed on‑chain identity attestations using SAS. (solana.com)
• Chainlink Functions and Data Streams enable DON‑verified API access and low‑latency feeds. (docs.chain.link)
• Space and Time’s Proof of SQL integrates with BigQuery for ZK‑verified analytics to smart contracts. (cloud.google.com)
• Axiom/Herodotus/Wormhole+Succinct provide ZK/state proofs for onchain history and cross‑chain security. (axiom.xyz)

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