Create or build a client

Create an account SigningKey

This code defines two functions that convert different types of Ethereum accounts—Externally Owned Accounts (EOAs) and Smart Contract Wallets (SCWs)—into a unified Signer interface. This ensures that both account types conform to a common interface for message signing and deriving shared secrets as per MLS (Message Layer Security) requirements.

• For an EOA, the convertEOAToSigner function creates a signer that can get the account address and sign messages and has placeholder methods for wallet type, chain ID, and block number.

  React Native

  // Example EOA
  export function convertEOAToSigner(eoaAccount: EOAAccount): Signer {
    return {
      getAddress: async () => eoaAccount.address,
      signMessage: async (message: string | Uint8Array) =>
        eoaAccount.signMessage({
          message: typeof message === 'string' ? message : { raw: message },
        }),
      walletType: () => undefined, // Default: 'EOA'
      getChainId: () => undefined,
      getBlockNumber: () => undefined,
    }
  }

• For an SCW, the convertSCWToSigner function similarly creates a signer but includes specific implementations for wallet type and chain ID, and an optional block number computation.

  React Native

  // Example SCW
  export function convertSCWToSigner(scwAccount: SCWAccount): Signer {
    return {
      getAddress: async () => scwAccount.address,
      signMessage: async (message: string) => {
        const byteArray = await scwAccount.signMessage(message)
        return ethers.utils.hexlify(byteArray) // Convert to hex string
      },
      walletType: () => 'SCW',
      getChainId: async () => 8453, // https://chainlist.org/
      getBlockNumber: async () => undefined, // Optional: will be computed at run
    };
  }

Create an XMTP client

Create an XMTP MLS client that can use the signing capabilities provided by the SigningKey parameter. This SigningKey links the client to the appropriate EOA or SCW.

Client.createV3(SigningKey, {
    env: 'production', // 'local' | 'dev' | 'production'
    enableV3: true,
    dbEncryptionKey: keyBytes, // 32 bytes
  })

Should work the same as it does in V2 Client.create(SigningKey, ClientOptions)