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Wallet Signatures

AuthSigs​

To use Lit Protocol, you must present a wallet signature obtained from the user. This is refered to an as AuthSig in the documentation. You can use any EIP 4361 compliant signature (Sign in with Ethereum) for the authSig, but you must put the signature into the AuthSig data structure format (documented here). You do not need to use the Lit JS SDK V2 to obtain the signature as long as it's EIP 4361 compliant and in the AuthSig data structure format.

Format of AuthSig​

The AuthSig should match this format.

An example AuthSig:

{
    "sig": "0x18720b54cf0d29d618a90793d5e76f4838f04b559b02f1f01568d8e81c26ae9536e11bb90ad311b79a5bc56149b14103038e5e03fee83931a146d93d150eb0f61c",
    "derivedVia": "web3.eth.personal.sign",
    "signedMessage": "localhost wants you to sign in with your Ethereum account:\n0x1cD4147AF045AdCADe6eAC4883b9310FD286d95a\n\nThis is a test statement.  You can put anything you want here.\n\nURI: https://localhost/login\nVersion: 1\nChain ID: 1\nNonce: gzdlw7mR57zMcGFzz\nIssued At: 2022-04-15T22:58:44.754Z",
    "address": "0x1cD4147AF045AdCADe6eAC4883b9310FD286d95a"
}

Obtaining the AuthSig​

You can use the built in checkAndSignAuthMessage() function to obtain the authSig. For example:

var authSig = await LitJsSdk.checkAndSignAuthMessage({
  chain: "ethereum",
});

This will trigger a wallet selection popup on the user's browser. The user will be asked to sign a message proving they own their crypto address. The message will be signed with their crypto address. The signature will be returned to you as the authSig variable. You will need to pass this to the Lit Protocol API.

This function will save the AuthSig to local storage so that the user does not need to sign the message again. However, the user may be asked to sign it again if the signature has expired or is too old.

This function will also check the currently selected chain in the user's wallet, and if their wallet supports it, sends a request to their wallet to change to the chain passed into the checkAndSignAuthMessage() function. This is to ensure that the user is using the correct chain.

Account Abstraction EIP1271 signatures​

note

Currently works only on the serrano litNetwork. Coming soon on the jalapeno litNetwork.

Currently, Externally-owned accounts (EOA) can interface with Lit via an authSig. With this paradigm, a private key is needed to sign an authSig. Smart contracts generally can not produce an authSig since they don't have a private key. However, this tutorial will show you how to generate an authSig for smart contracts using EIP1271. EIP-1271 is a standard to verify a signature when the account is a smart contract.

How to structure the AuthSig​

The format of the authSig remains the same as noted in the API docs.

  • sig is the actual hex-encoded signature.
  • derivedVia should be "EIP1271" to tell the nodes that the authSig is for smart contracts
  • signedMessage is any string that you want to pass to the isValidSignature(bytes32 _hash, bytes memory _signature) as its 1st arguement. It will be converted to bytes32 before calling the smart contract function
  • address of the smart contract you want to present the authSig for. Note that it should implement the isValidSignature(bytes32 _hash, bytes memory _signature) function.

For example:

{
    "sig": "0x18720b54cf0d29d618a90793d5e76f4838f04b559b02f1f01568d8e81c26ae9536e11bb90ad311b79a5bc56149b14103038e5e03fee83931a146d93d150eb0f61c",
    "derivedVia": "EIP1271",
    "signedMessage": "_hash message",
    "address": "0x6FdF5aD7f256D9677eC1d6B7e633Ff1E7FA5Ac14"
}

Now you can use the above authSig object in the Lit functions just as an any other authSig.

const encryptedSymmetricKey = await window.litNodeClient.saveEncryptionKey({
  accessControlConditions,
  symmetricKey,
  authSig,
  chain
})

How it works​

The Lit nodes call the isValidSignature(bytes32 _hash, bytes memory _signature) function for the contract at the authSig.address. Where bytes32 _hash is the bytes32 representation of the authSig.signedMessage and authSig.sig is passed as the bytes _signature argument. The authSig is validated based on the returned result of the contract's isValidSignature function.

Please read the EIP1271 docs to understand the isValidSignature function.

See it in action!​

Below is the complete React project.

Clearing the stored AuthSig​

If you want to clear the authSig stored in the browser local storage, you can call the disconnectWeb3 method.