Signing a Stamped Mandate

A is a user’s signed authorisation for a set of scoped actions. A Stamped Mandate is delivered over the API as a PINT (header x-sumvin-pint-token). Once you’ve constructed a PINT payload, it needs to be signed before it can be exchanged for a JWT. The Sumvin ecosystem supports two signer types, each using different cryptographic curves and verification methods.

Signer Types

Signer Type	Key Curve	Verification Method	Use Case
`user`	secp256k1	Standard ECDSA recovery	User signing directly via wallet
`agent`	P-256 (secp256r1)	EIP-1271 `isValidSignature` against Safe contract	AI agent signing on user’s behalf

The SIS automatically determines the signer type based on whether the signing wallet has a registered agent key.

User Signing (secp256k1)

When the user signs directly, use standard Ethereum EIP-712 signing via their wallet. This is the most common path for user-initiated flows.

TypeScript (viem)

import { createWalletClient, custom } from "viem";
import { sei } from "viem/chains";

const walletClient = createWalletClient({
  chain: sei,
  transport: custom(window.ethereum),
});

const domain = {
  name: "Sumvin Purchase Intent",
  version: "1",
  chainId: 1329n,
  verifyingContract: "0xE23c9A70BC749EBddd8c78a864fd911D04E9e992",
} as const;

const types = {
  PurchaseIntent: [
    { name: "wallet", type: "address" },
    { name: "nonce", type: "uint256" },
    { name: "statement", type: "string" },
    { name: "scopes", type: "string[]" },
    { name: "resources", type: "string[]" },
    { name: "maxAmount", type: "uint256" },
    { name: "maxAmountToken", type: "address" },
    { name: "expiresAt", type: "uint256" },
  ],
} as const;

const message = {
  wallet: "0xE23c9A70BC749EBddd8c78a864fd911D04E9e992",
  nonce: 42n,
  statement: "Purchase authorization for partner X",
  scopes: ["sr:us:pint:identity:proof_of_personhood", "sr:us:pint:personalization:read"],
  resources: ["sr:us:pint:abc123"],
  maxAmount: 0n,
  maxAmountToken: "0x0000000000000000000000000000000000000000",
  expiresAt: 1740000000n,
};

const signature = await walletClient.signTypedData({
  account: "0xUserEOAAddress...",
  domain,
  types,
  primaryType: "PurchaseIntent",
  message,
});

// signature is a hex string: "0x..."

Python (eth-account)

from eth_account import Account
from eth_account.messages import encode_typed_data

domain_data = {
    "name": "Sumvin Purchase Intent",
    "version": "1",
    "chainId": 1329,
    "verifyingContract": "0xE23c9A70BC749EBddd8c78a864fd911D04E9e992",
}

message_types = {
    "PurchaseIntent": [
        {"name": "wallet", "type": "address"},
        {"name": "nonce", "type": "uint256"},
        {"name": "statement", "type": "string"},
        {"name": "scopes", "type": "string[]"},
        {"name": "resources", "type": "string[]"},
        {"name": "maxAmount", "type": "uint256"},
        {"name": "maxAmountToken", "type": "address"},
        {"name": "expiresAt", "type": "uint256"},
    ]
}

message_data = {
    "wallet": "0xE23c9A70BC749EBddd8c78a864fd911D04E9e992",
    "nonce": 42,
    "statement": "Purchase authorization for partner X",
    "scopes": ["sr:us:pint:identity:proof_of_personhood", "sr:us:pint:personalization:read"],
    "resources": ["sr:us:pint:abc123"],
    "maxAmount": 0,
    "maxAmountToken": "0x0000000000000000000000000000000000000000",
    "expiresAt": 1740000000,
}

signable = encode_typed_data(
    domain_data, message_types, message_data, "PurchaseIntent"
)

signed = Account.sign_message(signable, private_key="0xYourPrivateKey...")
signature = signed.signature.hex()

Agent Signing (P-256)

When an AI agent signs a Stamped Mandate on the user’s behalf, it uses a P-256 key that has been registered as an authorised signer on the user’s Safe smart account. Verification happens on-chain via EIP-1271 — the SIS calls isValidSignature on the Safe contract to confirm the agent key is authorised.

import { p256 } from "@noble/curves/p256";

// Agent's P-256 private key
const agentPrivateKey = new Uint8Array(/* ... */);

// Hash the EIP-712 typed data (same hash as user signing)
const typedDataHash = hashTypedData({ domain, types, primaryType: "PurchaseIntent", message });

// Sign with P-256
const sig = p256.sign(typedDataHash.slice(2), agentPrivateKey);
const signature = "0x" + sig.toDERHex();

When exchanging an agent-signed PINT, the SIS detects the agent key automatically — no need to specify signer_type in the request:

{
  "pint": { "...": "..." },
  "signature": "0x...",
  "audience": "partner-x.example.com"
}

Agent signing requires the P-256 key to be registered on the user’s Safe contract. If the key is not an authorised signer, the EIP-1271 verification will fail with error code PINT-401-002.

After Signing

Once you have the signed Stamped Mandate — the PINT payload and its signature — pass both to the token exchange endpoint to receive a SIS-signed JWT.

Sigil — Identity & Mandates

Verifier Guide

API Reference

Signing a Stamped Mandate

Signer Types

User Signing (secp256k1)

TypeScript (viem)

Python (eth-account)

Agent Signing (P-256)

After Signing

​Signer Types

​User Signing (secp256k1)

​TypeScript (viem)

​Python (eth-account)

​Agent Signing (P-256)

​After Signing

Signer Types

User Signing (secp256k1)

TypeScript (viem)

Python (eth-account)

Agent Signing (P-256)

After Signing