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Using a Delegation Auth Sig to Make Requests

When making requests to the Lit network, you must provide Session Signatures. When making requests to the network that require payment, you must also attach a Capacity Delegation Auth Signature to your Session Signatures. This Auth Sig tells the Lit network which Capacity Credit to use for paying for your network usage, and also acts as proof that you have permission to use the Capacity Credit for payment.

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To learn more about what a Capacity Credit is, and how they're used, go here.

To learn about how to obtain a Capacity Delegation Auth Signature, go here.

For an overview of what requests to the Lit network require payment, go here.

The following code will demonstrate executing a Lit Action, one of the types of requests that requires payment, using Session Signatures that contain a Capacity Delegation Auth Signature.

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The full implementation of the code used in this guide can be found here.

Prerequisites​

Before continuing, you should have an understanding of:

note

The address we will be using to make a request to the Lit network needs to have been included in the delegateeAddresses for the Capacity Delegation Auth Signature used in this guide.

Setup​

Installing the Required Dependencies​

This guide makes use of the following packages and are required to use the following code. You can install the dependencies from NPM using NPM or Yarn:

npm install \
@lit-protocol/constants \
@lit-protocol/lit-node-client \
@lit-protocol/auth-helpers \
ethers@v5

Instantiating an Ethers Signer​

import ethers from "ethers";
import { LIT_RPC, LIT_ABILITY } from "@lit-protocol/constants";

const ethersSigner = new ethers.Wallet(
    process.env.ETHEREUM_PRIVATE_KEY,
    new ethers.providers.JsonRpcProvider(LIT_RPC.CHRONICLE_YELLOWSTONE)
);
note

The address corresponding to process.env.ETHEREUM_PRIVATE_KEY needs to have been included in the delegateeAddresses for the Capacity Delegation Auth Signature used in this guide.

Instantiating a LitNodeClient Client​

import { LitNodeClient } from "@lit-protocol/lit-node-client";
import { LIT_NETWORK } from "@lit-protocol/constants";

litNodeClient = new LitNodeClient({
    litNetwork: LIT_NETWORK.DatilTest,
    debug: false,
});
await litNodeClient.connect();

You can learn more about the @lit-protocol/lit-node-client package and what is offers using the API reference docs.

Generating Session Sigs with the Delegation Auth Sig​

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For more information on how the getSessionSigs works and it's parameters, please go here.

const sessionSigs = await litNodeClient.getSessionSigs({
    chain: "ethereum",
    expiration: new Date(Date.now() + 1000 * 60 * 60 * 24).toISOString(), // 24 hours
    capabilityAuthSigs: [capacityDelegationAuthSig],
    resourceAbilityRequests: [
    {
        resource: new LitActionResource("*"),
        ability: LIT_ABILITY.LitActionExecution,
    },
    ],
    authNeededCallback: async ({
        resourceAbilityRequests,
        expiration,
        uri,
    }) => {
    const toSign = await createSiweMessageWithRecaps({
        uri: uri!,
        expiration: expiration!,
        resources: resourceAbilityRequests!,
        walletAddress: ethersSigner.address,
        nonce: await litNodeClient.getLatestBlockhash(),
        litNodeClient,
    });

    return await generateAuthSig({
        signer: ethersSigner,
        toSign,
    });
    },
});

This line from the above code is how we're specifying the Capacity Delegation Auth Signature (that's delegating credit usage to ethersSigner.address) to pay for our request later in this guide:

capabilityAuthSigs: [capacityDelegationAuthSig]

Making a Request​

After executing the above code, you will now have Session Signatures that contain a Capacity Delegation Auth Signature. These Session Signatures can be used to make any requests to the Lit network that require payment.

Here is an example of using the Session Signatures to execute a simple Lit Action:

await litNodeClient.executeJs({
    sessionSigs,
    code: `(() => console.log("It works!"))();`,
});

Summary​

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The full implementation of the code used in this guide can be found here.

This guide has demonstrated how to use a Capacity Delegation Auth Signature to generate Session Signatures, and use those Session Signature to make a request to the Lit network that requires payment.