beskay / ethereum-offline-tx

Transaction helper for offline transactions

Sign and Send Offline Transactions

A web app and CLI tool to send transactions from an airgapped device.

Right now the development is halted, there are a few things left on the todo list which have to be implemented at a later date (from me -- or maybe from you if you want to contribute :) )

• The web app is not done yet and doesnt run on an offline computer, need to figure out how to support this
• Rewrite the CLI tool in Golang/Rust/C, basically any compiled language. OR use the recently released NodeJS single executable file. The goal is to not requiring NodeJS preinstalled on the airgapped device.

Web app

A web interface to simplify the process of sending an offline transaction, built with React.js and TypeScript.

Right now only basic Ether transfers are supported, but smart contract interactions will follow soon.

Demo

Getting started

1. Clone this repository on your online computer

git clone [e-mail]:beskay/ethereum-offline-tx.git

2. In a terminal, run npm install to install the required dependencies

cd ethereum-offline-tx
cd webapp
npm install

CLI-Tool

Simple command-line interface to send transactions from an offline ethereum wallet.

Prerequisites

• Node.js installed
• A valid Etherscan API key -> Getting an Etherscan API key

If you dont have Node.js installed on your offline computer, visit the official download page. Its possible to install node without an internet connection.

Getting Started

1. Clone this repository on your online computer

git clone [e-mail]:beskay/ethereum-offline-tx.git

2. In a terminal, run npm install to install the required dependencies

cd ethereum-offline-tx
cd CLI
npm install

3. Zip and copy the folder to your offline computer

Creating and sending a transaction

ON YOUR OFFLINE COMPUTER

1. Replace the example transaction in signTx.js with the actual tx you want to submit, see appendix for a short explanation of the transaction fields.

2. Run node signTx.js "YOUR_PRIVATE_KEY"

3. Copy the generated tx.json file to a USB drive

ON YOUR ONLINE COMPUTER

1. Copy tx.json from your USB drive to this directory

2. Run node sendTx.js "ENDPOINT_URL" "YOUR_ETHERSCAN_API_KEY", e.g. node sendTx.js "https://api.etherscan.io/" "AA456 ... 2E" for mainnet

3. Double check the tx you want to send, if everything is correct type yes and hit enter

4. Done!

Scripts

• getPrivatekey.js

Prints the first 10 addresses + corresponding privatekey from a given mnemonic. Usage:

node scripts/getPrivatekey.js "your mnenmonic phrase"

• signMessage.js

Signs a given message with given private key. Replace message in signMessage.js and run

node scripts/signMessage.js "YOUR_PRIVATE_KEY"

Further info

• List of endpoint URLs
• List of chain IDs

Credits to repository ethereum-raw-transactions, which was used as a template.

Appendix

Transaction fields

Parameter	Description
to	the address to send Ether to
value	the amount of Ether to send
data	arbitrary data for contract calls, first four bytes specify which function to call, the rest are the function arguments, set it to "" for basic Ether transfers
gasLimit	the maximum units of gas to consume, 21000 for basic Ether transfers
maxPriorityFeePerGas	tip paid to miners, introduced in EIP-1559
maxFeePerGas	maximum price paid per unit of gas, introduced in EIP-1559
nonce	number of transactions sent from the address, set to 0 for the first tx
type	set to 0x2, to denote EIP-1559 type transactions
chainId	chainId to send the transaction (e.g. 1 for mainnet, 5 for goerli test network, ...)

More info on transactions, especially more in-depth explanation of the data field, see also the transactions chapter of the Ethereum book.