Standards & EIPs

NEUS runs a single hub on Base Sepolia (chainId = 84532) today. All SDK/API payloads use numeric chain IDs. We do not pass CAIP strings in requests. Off-chain auth uses EIP-191 with a canonical NEUS message.

We support EOAs and smart accounts (EIP-1271 / EIP-6492). Cross-chain propagation uses ERC-7683-compatible vouchers anchored by qHash.

When we move to mainnet, only hub and target chains change and proof data remains stable.

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Core Standards

Chain IDs

• Numeric chain IDs only in SDK/API and in signed messages (e.g., 1, 8453, 84532).

• Hub (enforced): PRIMARY_CHAIN_ID = 84532 (Base Sepolia).

Identity (DIDs)

• did:pkh (did:pkh:eip155:<chainId>:<address>) stored and emitted in proofs.

• We may show CAIP strings in UI/docs, but we don’t send them in requests and don’t store them except as part of the DID string.

Off-chain Signatures (used today)

• EIP-191 (“personal_sign”) with a canonical NEUS message:

  NEUS Verification Request
  Wallet: 0x<lowercased address>
  Chain: 84532
  Verifiers: ownership-basic, ...
  Data: <deterministic JSON of the request payload>
  Timestamp: <unix ms, freshness window enforced>

• Server rebuilds/validates this and enforces PRIMARY_CHAIN_ID (84532).

Signature Contract (Normative)

Signature standard: EIP-191 (“personal_sign”). Hub chain (enforced): 84532 (Base Sepolia). Smart accounts: EIP-1271 and EIP-6492 are supported server-side.

1. Canonical message (exactly 6 lines, exact order)

NEUS Verification Request
Wallet: 0x<lowercased address>
Chain: 84532
Verifiers: <comma-separated verifier ids>
Data: <deterministic JSON of request.data>
Timestamp: <unix ms>

– Wallet MUST be lowercased inside the message. – Chain MUST be the numeric hub chain id (84532). – Verifiers MUST list the same IDs sent in verifierIds. – Data MUST be the deterministic JSON of the data object only. – Timestamp MUST be Unix milliseconds.

1. Deterministic JSON (Normative)

– Objects: sort keys ordinal; omit undefined; keep null. – Arrays: preserve order; canonicalize elements recursively. – Strings: standard JSON escaping. – Numbers: culture-invariant decimal with a dot (.). – No extra whitespace (no pretty print).

1. What is signed vs. what is sent

– The six-line message above is what gets signed. – The HTTP body includes walletAddress, signature, signedTimestamp, chainId, verifierIds, data, [options...]. – options are not included in the signed message.

1. Freshness and errors

– Freshness window: signatures older than 5 minutes or >1 minute in the future are rejected. – Typical errors: SIGNATURE_VERIFICATION_FAILED, SIGNATURE_EXPIRED, PAYLOAD_INVALID.

Smart Account Signatures

• EIP-1271: contract-wallet validation when EOA recovery fails.

• EIP-6492: detect/unwrap pre-deployment (counterfactual) signatures.

• Both are implemented.

On-chain Transactions

• EIP-155 applies automatically to on-chain tx (e.g., the hub transaction stored in hubTransaction).

• We do not use EIP-155 for off-chain auth.

Cross-chain Vouchers (propagation)

• ERC-7683-compatible, one voucher per target chain, all anchored by qHash.

  struct Voucher {
      bytes32 qHash;          // NEUS verification anchor
      uint256 sourceChainId;  // hub chain (84532 today)
      uint256 targetChainId;  // numeric
      address relayer;
      uint256 expiry;
      bytes   proof;          // opaque verifier/proof payload
  }

Cryptography

• SHAKE-256 → qHash (anchor for proofs/vouchers/storage references).

• ECDSA secp256k1 → wallet signatures; EIP-1271/6492 for smart accounts.

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What’s not used right now

• CAIP-2 in requests: Not used. CAIP for docs/DIDs only.

• EIP-712: Not used yet. (Planned; see “Future” below.)

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Minimal examples

SDK/API payload

const proof = await client.verify({
  verifier: 'ownership-basic',
  content: 'Hello NEUS...',
  options: {
    // spoke chains (if any). hub is implicit (84532) and enforced server-side.
    targetChains: [421614, 11155111], 
    privacyLevel: 'public',
    storeOriginalContent: true,
    enableIpfs: true
  },
  meta: {
    tags: ['campaign', 'proof-of-support']
  }
});

Stored proof (key fields)

• did: did:pkh:eip155:84532:<wallet>

• hubTransaction.chainId: 84532

• verifierContentHash: hex string

• options.privacyLevel: 'public' | 'private'

• Originals stored only when privacyLevel === 'public' and storeOriginalContent === true.

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Implementation checklist

• Chain IDs: numeric everywhere in code; do not send CAIP strings in requests.

• Hub enforcement: server validates Chain: 84532 in the signed message.

• Signatures: EIP-191 canonical message; freshness window enforced; address lowercased in message.

• Smart accounts: support EIP-1271 and EIP-6492 paths.

• Vouchers: ERC-7683-compatible; one target per voucher; anchor by qHash.

• Content proofs: verifiers emit hashed content verifierContentHash; original content stored only if public + storeOriginalContent=true.

• OAuth: code + PKCE; do not retain tokens; store only non-sensitive public identifiers if needed.

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Future (what we’ll add when ready)

• Hub switch: changed to Base mainnet; everything else unchanged.

• Additional spokes: expand targetChains set (still numeric).

• ZK circuits: more verifiers using zk (RISC-Zero/STARK); current verifiers may mark zk_not_required.