Introduction

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Circuitpython module for ethereum wallet creation and signing

Dependencies

This driver depends on:

• Adafruit CircuitPython <https://github.com/adafruit/circuitpython>_

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle <https://circuitpython.org/libraries>_ or individual libraries can be installed using circup <https://github.com/adafruit/circup>_.

Installing from PyPI

On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI <https://pypi.org/project/circuitpython-miniethers/>_. To install for current user:

.. code-block:: shell

pip3 install circuitpython-miniethers

To install system-wide (this may be required in some cases):

.. code-block:: shell

sudo pip3 install circuitpython-miniethers

To install in a virtual environment in your current project:

.. code-block:: shell

mkdir project-name && cd project-name
python3 -m venv .venv
source .env/bin/activate
pip3 install circuitpython-miniethers

Installing to a Connected CircuitPython Device with Circup

Make sure that you have circup installed in your Python environment. Install it with the following command if necessary:

.. code-block:: shell

pip3 install circup

With circup installed and your CircuitPython device connected use the following command to install:

.. code-block:: shell

circup install miniethers

Or the following command to update an existing version:

.. code-block:: shell

circup update

Usage Example

Simple example showcasing wallet creation and message signing.

.. code-block:: python

from circuitpython_miniethers import Signature, Wallet

# The private key is used for both signing methods
# IMPORTANT: In a real app, never hardcode private keys.
# Use environment variables or a secure wallet connection.
privateKey = "0x022b99092266a16a949e6a450f0e88a8288d39d5f1d75c00575a35a0ba270dbc"

# Create a wallet instance from the private key
wallet = Wallet(privateKey)


def generateFlatSignature():
    """
    Signs a simple string message (ERC-191).
    """
    print("--- Signing a Flat String (ERC-191) ---")

    # The message to sign
    message = "hello"

    print(f'Signing message: "{message}"')
    print(f"Signer Address: {wallet.address}")
    print("---")

    flatSignature = wallet.signMessage(message)

    print("Full Flat Signature:", flatSignature)

    # For comparison, let's split the signature into its components
    signature = getattr(Signature, "from")(flatSignature)
    print("Signature Components:")
    print("  r:", signature.r)
    print("  s:", signature.s)
    print("  v:", signature.v)
    print("-----------------------------------------\n")


def signTypedDataMail():
    """
    Signs structured typed data (EIP-712).
    This provides more readable and secure signing prompts in wallets like MetaMask.
    """
    print("--- Signing Typed Data (EIP-712) ---")

    # 1. The Domain Separator: Defines the context of the signature.
    # This prevents a signature from being valid in a different application.
    domain = {
        # The user-friendly name of the signing domain
        "name": "Ether Mail",
        # The current version of the signing domain
        "version": "1",
        # The chain ID of the intended network (1 for Ethereum Mainnet)
        "chainId": 1,
        # The address of the contract that will verify the signature
        "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC",
    }

    # 2. The Types: Defines the structure of the data being signed.
    # You define your primary type ("Mail") and any custom nested types ("Person").
    types = {
        "Person": [
            {"name": "name", "type": "string"},
            {"name": "wallet", "type": "address"},
        ],
        "Mail": [
            {"name": "from", "type": "Person"},  # Nested custom type
            {"name": "to", "type": "Person"},  # Nested custom type
            {"name": "contents", "type": "string"},
        ],
    }

    # 3. The Value: The actual data object to be signed.
    # This object must match the structure defined in `types`.
    value = {
        "from": {
            "name": "Cow",
            "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826",
        },
        "to": {
            "name": "Bob",
            "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB",
        },
        "contents": "Hello, Bob! This is a typed message.",
    }

    print("Signing EIP-712 data for address:", wallet.address)
    print("Domain:", domain)
    print("Value:", value)
    print("---")

    # The `_signTypedData` method handles hashing the structured data according to the EIP-712 spec.
    signature = wallet._signTypedData(domain, types, value)

    print("EIP-712 Signature:", signature)
    print("------------------------------------\n")


# Run both signing functions
def main():
    print("CircuitPython MiniEthers - Ethers.js Compatibility Test\n")
    print(f"Wallet Address: {wallet.address}")
    print(f"Private Key: {wallet.privateKey}")
    print(f"Public Key: {wallet.publicKey}\n")

    generateFlatSignature()
    signTypedDataMail()

    print("\n✅ All tests completed successfully!")


if __name__ == "__main__":
    main()

Documentation

API documentation for this library can be found on Read the Docs <https://circuitpython-miniethers.readthedocs.io/>_.

For information on building library documentation, please check out this guide <https://learn.adafruit.com/creating-and-sharing-a-circuitpython-library/sharing-our-docs-on-readthedocs#sphinx-5-1>_.

Contributing

Contributions are welcome! Please read our Code of Conduct <https://github.com/ShambaC/CircuitPython_MiniEthers/blob/HEAD/CODE_OF_CONDUCT.md>_ before contributing to help this project stay welcoming.

PS

I participated in EthGlobal New Delhi this year where me and my team created a hardware wallet for our project. For that purpose we chose a Raspberry Pi Pico. And that is when we realised that the hardware is pretty constrained which doesnt allow existing libraries to work. So I wrote a package that worked on the Pico.

And after some time I decided that I should package this properly and share it as a library, so that people can use this if they want to. That's the story behind this package.