Creating an external signer for EthSigner

EthSigner supports the addition of more external signers in same way as HashiCorp Vault.

To create an external signer:

1. Clone the EthSigner repository.

2. Create a Gradle module for the new signer in the ethsigner/signer directory.

3. To ensure the module for the new signer is built, add the module to the settings.gradle file.

4. In the new module, create a concrete child class of SignerSubCommand.

   The new SignerSubCommand must include the parameters (tagged with PicoCLI annotations) to initialize your signer.

5. Update the createSigner() function to be the entry point to create and return your signer. Your signer is exposed only as a TransactionSigner.

   note

   The new signing class is responsible for fulfilling the TransactionSigner interface. To fulfill the TransactionSigner interface, the class must be able to create a signature for a block of bytes and provide the address associated with the key pair in the signer. ::: 6. In EthSignerApp.java, register the new SignerSubCommand with the cmdLineParser as for existing signers.

6. Update the EthSigner::app module dependency list to include the module created in step 2.