This project is a work in progress. APIs and documentation may change.

SIWA

Trustless identity and authentication for AI agents. An open standard built on ERC-8004 and ERC-8128.

Give your agent one prompt and it will create a wallet, register onchain, and start authenticating.

Get Started GitHub

Read https://siwa.builders.garden/skill.md

1.Read the skill file above
2.Create your wallet & register onchain
3.Authenticate with any SIWA server

View skill.md

For Agents

Prove who you are

Read a skill file, get an onchain identity, and authenticate with any service — autonomously, without exposing your keys.

For Agent Builders

Give your agent an identity

For Platform Builders

Gate your platform for agents

Know which agent is calling your API. Verify its identity on every request — no API keys, no shared secrets.

Why SIWA

Keys never touch the agent

Private keys are stored in a separate secure service. The agent can request signatures but never access the key — even if the agent is compromised.

Identity lives onchain

Each agent gets an ERC-721 NFT on the Identity Registry. Transferable, verifiable, permanent — anyone can check it.

Works on any chain

Base, Ethereum, Linea, Polygon. Deploy on mainnet or testnets — wherever your agents live.

Open standard

MIT licensed, built on ERC-8004 and ERC-8128. Works with any agent framework — Claude, GPT, custom agents.

How It Works

Agent gets an identity

Create a wallet via the keyring proxy and register an onchain NFT on the Identity Registry.

Agent signs a message

Build a structured SIWA message and sign it. The private key never leaves the keyring.

Server verifies onchain

Check the signature, verify NFT ownership on the registry, and grant access.

Quickstart

Install the SDK and add two functions — one on the agent, one on the server.

$npm install @buildersgarden/siwa

agent.tsAgent

import { signSIWAMessage } from '@buildersgarden/siwa';

// address is resolved from the keystore
const { message, signature, address } = await signSIWAMessage(
  {
    domain: 'api.example.com',
    uri: 'https://api.example.com',
    agentId,
    agentRegistry,
    chainId,
    nonce,
    issuedAt: new Date().toISOString(),
  },
  keystoreConfig
);

server.tsServer

import { verifySIWA } from '@buildersgarden/siwa';
import { createPublicClient, http } from 'viem';

const client = createPublicClient({ transport: http() });

const result = await verifySIWA(
  message,
  signature,
  'api.example.com',
  (nonce) => nonceStore.check(nonce),
  client
);

// result.valid, result.address, result.agentId

Read the full docs Try it locally

Built On Open Standards

SIWA is MIT licensed, built on ERC-8004 and ERC-8128. No vendor lock-in, no proprietary protocols.