Summary: You can ship on public L1/L2s without opening the floodgates. This playbook shows how to design allowlist-grade access that satisfies DAC8/OFAC and enterprise procurement while preserving UX with ERC‑4337, EIP‑7702, EAS attestations, ERC‑3643, and privacy-preserving flows.

If your stakeholders demand “only approved counterparties touch our contracts,” this is how you implement it—without forking to a private chain.

The “White‑List” Architect: Designing Permissioned Access for Public Chains

Hook — The headache nobody budgeted for

Your legal team just flagged a blocker: beginning January 1, 2026, EU DAC8 requires crypto-asset service providers to collect, verify, and report user data, with first reporting due by September 30, 2027. Your procurement team insists on OFAC‑safe operations and geofencing from day one. Meanwhile, your product runs on public Ethereum and L2s—by design permissionless. How do you gate access, cross‑chain, and still hit the Q2 roadmap? (taxation-customs.ec.europa.eu)

To complicate it, Ethereum’s Pectra upgrade shipped account‑abstraction primitives (EIP‑7702), and ERC‑4337 paymasters are everywhere—amazing for UX, but they also expand the attack and policy surface you must control. (blog.ethereum.org)

Agitate — What’s at risk if you don’t architect the allowlist layer

• Missed compliance dates. DAC8 data collection started January 1, 2026. If your onboarding and on‑chain policies don’t align now, you’ll re‑do KYC, rebuild logs, and miss audit gates. (taxation-customs.ec.europa.eu)
• Sanctions exposure. OFAC expects crypto teams to design sanctions controls into product from day one (geo‑IP, list screening, governance). Violations and secondary‑sanctions risk have escalated alongside new designations. (davispolk.com)
• Fraud and exploit leakage. Chainalysis reports 2025 scam inflows of at least $14B (projected >$17B as attribution completes) and record state‑linked thefts. A porous access model invites ACT‑style “anyone‑can‑take” exploits and wallet‑level social engineering. (chainalysis.com)
• New AA pitfalls. Research has shown EIP‑7702 delegation can be phished for persistent control if you don’t constrain what code is allowed to execute—your allowlist must extend to wallet logic. (arxiv.org)

Bottom line: open‑by‑default contracts plus multi‑chain flows equals uncontrolled counterparty risk, audit gaps, and slippage on delivery dates.

Solve — 7Block Labs’ methodology for permissioned access on public chains

We design a policy‑driven “Allowlist Fabric” that rides on the public stack—no vendor lock‑in, no private forks—using standards your auditors will recognize.

1. Policy model and identity stack (week 1–2)

• Map policy to controls:
  • Regulatory: DAC8 (CARF‑aligned reporting), OFAC geo/list screening, and if EU‑facing B2B, eIDAS‑qualified seals for “Know‑Your‑Contract/Counterparty.” (taxation-customs.ec.europa.eu)
• Choose attestations:
  • EAS (Ethereum Attestation Service) for on‑chain, schema‑based eligibility (e.g., “Passed KYC,” “Accredited Investor”) with resolver hooks your contracts can verify in constant time. EAS is live across mainnet/L2s with millions of attestations, making it battle‑tested for gating. (easscan.org)
  • zk‑credentials via Privado ID (formerly Polygon ID) for privacy‑preserving KYC/KYB: prove “over‑18,” “EU tax resident,” or “accredited” without revealing PII; on‑chain verifiers and tutorials exist today. (kaleido.io)
  • For regulated RWAs, use ERC‑3643 permissioned tokens (ONCHAINID under the hood) to enforce identity‑based transfer controls at the token layer; the standard is backed by major institutions and progressing toward ISO standardization. (tokeny.com)

1. Contract‑level allowlists (week 2–4)

• Solidity patterns we implement and audit:
  • Attestation‑gated entry points. Your core functions check an EAS schema or zk‑proof before execution; no PII is stored on‑chain.
  • Role‑based fallbacks for ops (OpenZeppelin AccessControl) but all end‑user paths are attestation‑gated to keep support load down.
  • Merkle‑proof allowlists only where static (e.g., one‑off presales). For dynamic programs, attestation or signature‑based whitelisting beats Merkle in both gas and ops overhead; OZ 5.x and patched Merkle libs reduce risk. Typical gas: ~30k for Merkle proof, ~8–36k for signature checks (chain‑dependent). (bomberbot.com)

Example: EAS‑gated function (EVM)

interface IEAS {
  function isAttested(bytes32 schema, address subject) external view returns (bool);
}

contract GatedVault {
  IEAS public eas;
  bytes32 public constant SCHEMA_KYC = 0x...; // "Passed KYC" schema UID

  constructor(address _eas){ eas = IEAS(_eas); }

  function deposit() external payable {
    require(eas.isAttested(SCHEMA_KYC, msg.sender), "KYC attestation required");
    // business logic
  }
}

1. Wallet and gas policy with ERC‑4337 + EIP‑7702 (week 3–5)

• Whitelist Paymaster: sponsor gas only for attested users/operations; rate‑limit and revoke centrally without touching business contracts. Use 4337 v0.9 paymaster signatures to parallelize signing and cut latency. (docs.erc4337.io)
• Safe 7702 delegation: restrict delegate targets to a vetted registry so a phished 7702 authorization cannot route to arbitrary code. We apply audit rules derived from recent attack research. (arxiv.org)

Example: 4337 Whitelist Paymaster (sketch)

contract WhitelistPaymaster is IPaymaster {
  mapping(address=>bool) public allowed;
  IEAS public eas;
  bytes32 public constant SCHEMA_KYB = 0x...;

  function validatePaymasterUserOp(
    UserOperation calldata uo, bytes32, uint256
  ) external view returns (bytes memory, uint256) {
    require(allowed[uo.sender] || eas.isAttested(SCHEMA_KYB, uo.sender),
      "Not allowlisted/attested");
    return ("", 0); // sponsor
  }
}

1. Cross‑chain allowlists that actually work (week 4–6)

• Intents as the policy choke‑point. Standardize cross‑chain movement behind ERC‑7683 so your “who can fill/settle” rules apply everywhere. Intents expose a single place to enforce allowlists instead of bespoke bridge code per chain. (eips.ethereum.org)
• Token movement with controls. Where you need cross‑chain tokenization, leverage Chainlink CCIP’s Cross‑Chain Tokens (CCT) and management tooling, then bind fills/receipts to your allowlist registry. For confidential flows (e.g., fund subscriptions), plan to use Chainlink Confidential Compute early‑access in 2026 to validate identity/compliance with private inputs. (chain.link)

1. Compliance automation and audit‑grade logging (week 2–8)

• DAC8/CARF fields captured at onboarding and referenced via attestations on‑chain; operational logs preserve the who/what/when without storing PII on-chain.
• Sanctions controls addressed in product design: IP/geo blocking, counterparty screening, and kill‑switches per OFAC guidance. (davispolk.com)

1. Security hardening you can defend in a board meeting

• Libraries: OpenZeppelin 5.x (gas‑reduced, custom errors), patched Merkle multiproof (≥4.9.2), AA modules from OZ 5.2 for cross‑chain/AA support. (blog.openzeppelin.com)
• Runtime guards: circuit‑breakers, rate limits, and “deny by default” on bridges/fillers until identity attested.

Practical examples you can ship in 2026

1. Permissioned RWA on a public L2, investor‑friendly UX

• Token standard: ERC‑3643 so transfers only succeed between attested holders; issuers retain limited control functions for recovery and forced transfers where law requires. (tokeny.com)
• Onboarding: Privado ID proof of “accredited” + “EU tax residency,” bound to ONCHAINID; 4337 paymaster sponsors first transfer. (kaleido.io)
• Cross‑chain: ERC‑7683 order to subscribe from Base → settle on Ethereum; fillers must be in the “Approved Fillers” attestation set; CCT for token movement. (eips.ethereum.org)
• Privacy: Confidential subscription amounts via Chainlink Confidential Compute run inside CRE—auditable, but not public. Early Access 2026. (blog.chain.link)

1. B2B payments network with eIDAS “Know‑Your‑Contract”

• Each corporate wallet presents a qualified electronic seal linked to EU trust lists; contracts verify seals on‑chain, making counterparty validation machine‑checkable. (arxiv.org)
• Result: instant mutual validation at first interaction—no pre‑arranged bilateral registry needed.

1. Consumer dApp with private age‑gated features

• “Over‑18” zk‑proof via Privado ID verified in‑contract; 4337 paymaster sponsors compliant users; metrics show drop in KYC abandonment versus traditional uploads. Tutorial and reference verifier code exist. (docs.privado.id)

Best emerging practices (Jan 2026)

• Make intents your control plane. Define who may create/fill/settle orders under ERC‑7683; one policy, many chains. (eips.ethereum.org)
• Bind wallet upgrades. With EIP‑7702 live, restrict delegate targets and require attestations for wallet‑level capabilities; teach your users to verify what they delegate. (blog.ethereum.org)
• Prefer attestations to static Merkle lists for anything dynamic; use Merkle only for fixed pre‑sales and ensure OZ multiproof patches are applied. (github.com)
• Use paymasters as policy enforcers, not just gas sponsors: whitelist patterns exist in 4337 docs; add revocation lists and rate‑limits. (docs.erc4337.io)
• For cross‑chain tokenization, adopt CCIP CCT and enforce allowlists at the token manager; plan for Confidential Compute when privacy or competitive data is in play. (chain.link)

Target audience and must‑use keywords

• Who this is for:

  • Heads of Digital Assets and Product at banks/fintechs launching RWAs on public L1/L2.
  • Compliance leaders implementing DAC8/CARF and OFAC controls in on‑chain products.
  • Web3 product managers building cross‑chain apps that must pass enterprise procurement.

• Keywords to include in your docs, RFPs, and architecture notes:

  • “DAC8 CARF reporting,” “MiCA CASP alignment,” “OFAC SDN geo‑IP controls,” “eIDAS qualified seal verification,” “EAS schema‑gated eligibility,” “ERC‑3643 permissioned token,” “ERC‑4337 whitelist paymaster,” “EIP‑7702 delegate registry,” “ERC‑7683 cross‑chain intents,” “Chainlink CCIP CCT,” “Confidential Compute (CRE).” (taxation-customs.ec.europa.eu)

GTM metrics we instrument from day one

• Compliance reliability
  • % of on‑chain calls blocked by allowlist policy (target: detect ≥99% of ineligible before state‑changing ops).
  • DAC8 data completeness at onboarding (target: ≥99.5%) and first‑pass audit success.
• Risk reduction
  • Address risk‑score coverage and “CEX proximity” heuristics to deter ACT‑style exploits. Track exploit attempt rejections and time‑to‑block. (arxiv.org)
• UX and conversion
  • KYC completion rate vs. baseline (expect uplift with zk‑proof flows); sponsored‑tx completion via 4337 (drop‑off <5%). (docs.privado.id)
• Cross‑chain reliability
  • ERC‑7683 order fill success and median time‑to‑finality with policy enforcement across origin/destination chains. (eips.ethereum.org)

What you get with 7Block Labs

• Architecture and implementation:
  • Attestation schemas, resolvers, and on‑chain registries.
  • 4337 paymasters (whitelist, verifying, ERC‑20) with revocation and rate limits.
  • ERC‑3643 tokenization flows for RWAs with ONCHAINID.
  • ERC‑7683 intent routers with filler allowlists and settlement adapters.
  • CCIP CCT managers with policy hooks; Confidential Compute integration plan. (tokeny.com)
• Security and audit:
  • OpenZeppelin 5.x baseline, patched Merkle, 7702 delegate‑safety review, and continuous monitoring. (blog.openzeppelin.com)
• Integration and procurement support:
  • Data pipelines for DAC8/CARF reporting fields, OFAC screening workflows, and enterprise SSO/KYB bridges into on‑chain attestations. (taxation-customs.ec.europa.eu)

Explore our services:

• Full‑stack delivery: blockchain development services
• On‑chain/identity engineering: web3 development services
• Compliance‑grade reviews: security audit services
• ERP/CRM/IdP plumbing: blockchain integration
• Cross‑chain and bridge work: cross‑chain solutions development and blockchain bridge development
• Launch support: fundraising and smart contract development

Brief in‑depth details you can hand to engineering

• EIP‑7702 guardrails:
  • Maintain a registry of approved delegate contracts; enforce checks in wallet factories; highlight risks from recent research in user flows. (arxiv.org)
• 4337 Paymaster specifics:
  • Use v0.9 paymaster signatures to parallelize signing and remove serialization bottlenecks; escrow adequate stake in EntryPoint; monitor sponsor exposure. (docs.erc4337.io)
• ERC‑7683 enforcement points:
  • Validate

    ResolvedCrossChainOrder

    against allowlist; reject unregistered fillers; emit auditable events for DAC8 provenance. (eips.ethereum.org)
• ERC‑3643 operations:
  • Encode compliance in transfer hooks; pair with ONCHAINID; document recovery and force‑transfer procedures for auditors. Institutionally recognized and moving toward ISO standardization. (tokeny.com)
• Privacy‑preserving compute:
  • For sensitive checks (KYB, allocations), plan Chainlink Confidential Compute workflows in 2026; keep proofs and policy artifacts on‑chain, inputs private. (blog.chain.link)
• Merkle vs signatures vs attestations:
  • For static lists: Merkle (~30k gas verify); for dynamic and per‑user controls: signature‑based or EAS/zk attestations; ensure OZ multiproof patches (≥4.9.2). (bomberbot.com)

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Ready to stop debating “public vs. private” and start shipping a compliant, allowlisted product?

If you’re a Head of Digital Assets targeting an ERC‑3643 RWA launch on an L2 in H1 2026, under DAC8 reporting and OFAC controls, book a 45‑minute White‑List Architecture Review with our CTO this week—we’ll map your attestation schemas, design your 4337 paymaster and 7702 delegate registry, and deliver a Gantt, risk register, and unit‑economics model you can take to procurement. Start here with our blockchain integration and follow‑on security audit services.