DataItem Signers

Every message sent to AO MUST be signed, aoconnect provides a helper function for signing messages or spawning new processes. This helper function createDataItemSigner is provided for arweave wallets. But you can create your own Signer instance too.

What is a Wallet/Keyfile?

A wallet/keyfile is a public/private key pair that can be used to sign and encrypt data.

What is an ao message/dataItem?

You often see the terms message and dataItem used interchangeably in the documentation, a message is a data-protocol type in ao that uses the dataItem specification to describe the messages intent. A dataItem is defined in the ANS-104 bundle specification. A dataItem is the preferred format of storage for arweave bundles. A bundle is a collection of these signed dataItems. A message implements specific tags using the dataItem specification. When developers send messages to ao, they are publishing dataItems on arweave.

🎓 To learn more about messages click here and to learn more about ANS-104 dataItems click here

What is a signer?

A signer is function that takes data, tags, anchor, target and returns an object of id, binary representing a signed dataItem. AO accepts arweave signers and ethereum signers. createDataItemSigner is a helper function that can take an arweave keyfile or a browser instance of an arweave wallet usually located in the global scope of the browser, when I user connects to a wallet using an extension or html app.

Examples

arweave keyfile

NOTE: if you do not have a wallet keyfile you can create one using npx -y @permaweb/wallet > wallet.json

import * as WarpArBundles from "warp-arbundles";

const pkg = WarpArBundles.default ? WarpArBundles.default : WarpArBundles;
const { createData, ArweaveSigner } = pkg;

function createDataItemSigner(wallet) {
  const signer = async ({ data, tags, target, anchor }) => {
    const signer = new ArweaveSigner(wallet);
    const dataItem = createData(data, signer, { tags, target, anchor });
    return dataItem.sign(signer).then(async () => ({
      id: await dataItem.id,
      raw: await dataItem.getRaw(),
    }));
  };

  return signer;
}

arweave browser extension

NOTE: This implementation works with ArweaveWalletKit, ArConnect, and Arweave.app

import { Buffer } from "buffer/index.js";
import * as WarpArBundles from "warp-arbundles";

if (!globalThis.Buffer) globalThis.Buffer = Buffer;
const { DataItem } = WarpArBundles;

function createDataItemSigner(arweaveWallet) {
  /**
   * createDataItem can be passed here for the purposes of unit testing
   * with a stub
   */
  const signer = async ({
    data,
    tags,
    target,
    anchor,
    createDataItem = (buf) => new DataItem(buf),
  }) => {
    /**
     * signDataItem interface according to ArweaveWalletConnector
     *
     * https://github.com/jfbeats/ArweaveWalletConnector/blob/7c167f79cd0cf72b6e32e1fe5f988a05eed8f794/src/Arweave.ts#L46C23-L46C23
     */
    const view = await arweaveWallet.signDataItem({
      data,
      tags,
      target,
      anchor,
    });
    const dataItem = createDataItem(Buffer.from(view));
    return {
      id: await dataItem.id,
      raw: await dataItem.getRaw(),
    };
  };

  return signer;
}

ethereum key

import { EthereumSigner, createData } from "@dha-team/arbundles";

function createDataItemSigner(wallet) {
  const signer = async ({ data, tags, target, anchor }) => {
    const signer = new EthereumSigner(wallet);
    const dataItem = createData(data, signer, { tags, target, anchor });
    return dataItem.sign(signer).then(async () => ({
      id: await dataItem.id,
      raw: await dataItem.getRaw(),
    }));
  };

  return signer;
}

Summary

Using the signer function developers can control how dataItems are signed without having to share the signing process with aoconnect.