Delegated Attestation API

The Delegated Attestation API enables gas-subsidized attestations on EAS. The attester signs an EIP-712 typed message in their wallet, then the server submits the transaction on their behalf, paying gas from a server-side delegate wallet.

This lets users create attestations without holding native tokens for gas.

How It Works

1. The client fetches the attester's current EAS nonce via GET /api/eas/nonce
2. The client builds an EIP-712 typed data structure and prompts the user to sign it
3. The client sends the signed data to POST /api/eas/delegated-attest
4. The server verifies the signature, checks schema eligibility, and submits the transaction via attestByDelegation on the EAS contract
5. The server returns the attestation UID and transaction hash

Endpoints

GET /api/eas/nonce

Returns the current EAS nonce for a given attester address. The nonce is required to build the EIP-712 typed data for signing.

Request

Parameter	Location	Type	Required	Description
attester	query	string	Yes	Ethereum address (0x-prefixed, 20 bytes)

Example Request

curl "https://reputation.omatrust.org/api/eas/nonce?attester=0x1234567890abcdef1234567890abcdef12345678"

Response (Success)

{
  "nonce": "0",
  "chain": "OMAchain Testnet",
  "chainId": 66238,
  "easAddress": "0x7946127D2f517c8584FdBF801b82F54436EC6FC7",
  "elapsed": "120ms"
}

Field	Type	Description
nonce	string	Current EAS nonce for the attester (stringified integer)
chain	string	Human-readable chain name
chainId	number	Chain ID
easAddress	string	EAS contract address on this chain
elapsed	string	Request duration

Errors

HTTP Status	Description
400	Missing or invalid attester parameter
500	EAS not configured or RPC failure

---

POST /api/eas/delegated-attest

Submits a signed delegated attestation to EAS. The server pays gas on behalf of the attester.

Request

Field	Type	Required	Description
attester	string	Yes	Ethereum address of the signer (0x-prefixed, 20 bytes)
signature	string	Yes	EIP-712 signature from the attester's wallet
delegated	object	Yes	The attestation data that was signed (see below)

delegated object

Field	Type	Description
schema	string	Schema UID (0x-prefixed, 32 bytes)
recipient	string	Attestation recipient address (0x-prefixed, 20 bytes)
expirationTime	number	Unix timestamp for expiration (0 for no expiration)
revocable	boolean	Whether the attestation can be revoked
refUID	string	Referenced attestation UID (0x000...000 for none)
data	string	ABI-encoded attestation data (0x-prefixed)
deadline	number	Unix timestamp after which the signature is invalid

Example Request

curl -X POST https://reputation.omatrust.org/api/eas/delegated-attest \
  -H "Content-Type: application/json" \
  -d '{
    "attester": "0x1234567890abcdef1234567890abcdef12345678",
    "signature": "0xabc123...signature...",
    "delegated": {
      "schema": "0x807b38ce9aa23fdde4457de01db9c5e8d6ec7c8feebee242e52be70847b7b966",
      "recipient": "0x0000000000000000000000000000000000000000",
      "expirationTime": 0,
      "revocable": true,
      "refUID": "0x0000000000000000000000000000000000000000000000000000000000000000",
      "data": "0x...",
      "deadline": 1739000000
    }
  }'

Response (Success)

{
  "success": true,
  "txHash": "0x...",
  "uid": "0x...",
  "blockNumber": 12345,
  "chain": "OMAchain Testnet",
  "elapsed": "3200ms"
}

Field	Type	Description
success	boolean	true
txHash	string	Transaction hash
uid	string | null	EAS attestation UID (parsed from the Attested event log)
blockNumber	number	Block number where the transaction was confirmed
chain	string	Human-readable chain name
elapsed	string	Request duration

Error Codes

HTTP Status	Code	Description
400	—	Missing required fields (delegated, signature, attester)
400	SIGNATURE_EXPIRED	The deadline has passed
400	INVALID_SIGNATURE	Signature format is invalid or cannot be verified
400	ATTESTER_MISMATCH	Recovered signer does not match the attester field
403	SCHEMA_NOT_SUBSIDIZED	Schema is not eligible for gas subsidy
409	DUPLICATE	This exact signature was already submitted (replay protection)
500	NO_DELEGATE_KEY	Server-side delegate wallet key is not configured
500	—	RPC failure, gas estimation failure, or transaction revert
501	MAINNET_NOT_SUPPORTED	Mainnet delegated attestations are not yet enabled

EIP-712 Typed Data

The attester signs an EIP-712 message with the following structure:

Domain

Field	Value
name	EAS
version	1.0.0
chainId	Target chain ID (e.g., 66238)
verifyingContract	EAS contract address

Types

Attest(
  address attester,
  bytes32 schema,
  address recipient,
  uint64 expirationTime,
  bool revocable,
  bytes32 refUID,
  bytes data,
  uint256 value,
  uint256 nonce,
  uint64 deadline
)

The nonce is fetched from the EAS contract via the nonce endpoint. The value is always 0 (no ETH attached).

Schema Eligibility

Only schemas on the subsidized allowlist are eligible for gas-subsidized delegated attestation. Submitting a non-subsidized schema returns 403 SCHEMA_NOT_SUBSIDIZED.

The active chain is determined by the NEXT_PUBLIC_ACTIVE_CHAIN environment variable on the server (omachain-testnet or omachain-mainnet).

Typical Integration Flow

┌──────────┐     ┌──────────────┐     ┌─────┐
│  Client   │     │  Reputation  │     │ EAS │
│ (browser) │     │   Server     │     │     │
└─────┬─────┘     └──────┬───────┘     └──┬──┘
      │                  │                │
      │ GET /api/eas/    │                │
      │ nonce?attester=  │                │
      │─────────────────>│                │
      │                  │  getNonce()    │
      │                  │───────────────>│
      │                  │<───────────────│
      │  { nonce }       │                │
      │<─────────────────│                │
      │                  │                │
      │ (build EIP-712   │                │
      │  typed data,     │                │
      │  prompt wallet   │                │
      │  signature)      │                │
      │                  │                │
      │ POST /api/eas/   │                │
      │ delegated-attest │                │
      │─────────────────>│                │
      │                  │ verify sig     │
      │                  │ check schema   │
      │                  │                │
      │                  │ attestByDelegation()
      │                  │───────────────>│
      │                  │<───────────────│
      │                  │                │
      │ { uid, txHash }  │                │
      │<─────────────────│                │