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Ethereum Tool

Command line tool for offline template-based transaction signing.

If you like this tool, please consider a donation at:



Download the latest ZIP from:

Install (Mac OS X, Linux, or FreeBSD) via:

sudo unzip -o -d /usr/local/


Run the tool via:


Offline key management

Reboot your machine using a Linux Live USB stick so you work in a clean and secure environment.

The password command might give you some inspiration for a strong password.

ethereum-tool password

Create a new key and corresponding transaction template via:

ethereum-tool createkey -d keystore -t templates

The keystore directory will contain the new key. The templates directory will contain the corresponding transaction template.

Store the key in a save way (e.g., multiple USB keys or so). The transaction template can be used to prepare transactions to be signed.

Verify the key via:

ethereum-tool verifykey -f keystore/UTC--...

You can also create a transaction template from an existing key via:

ethereum-tool verifykey -f keystore/UTC--... -t templates

Preparing a transaction

Preparing a transaction requires an online machine.

Copy the transaction template to a transaction.json file to prepare a new transaction.

You need to change some fields within the transaction.json file.

First of all the nonce need to be set correct. Retrieve the correct nonce of your address via:

ethereum-tool nonce -l http://localhost:8545 -a your_address_here

This of course requires a running and synched Ethereum node.

You also might want to adjust the gas price. Query the current gas price (as reported by your local node) via:

ethereum-tool gasprice -l http://localhost:8545

Notice that this might not be the sharpest gas price possible. Check out the network speed to see the currently used gas prices:

ethereum-tool speed -l http://localhost:8545

Offline transaction signing

After the transaction JSON file has been prepared we boot again via our Linux Live USB to have a clean and secure environment.

Sign the transaction via:

ethereum-tool sign -f keystore/UTC--... -t transaction.json -o transaction

Inspect the signed transaction via:

ethereum-tool inspect -f transaction

Transmitting the transaction

This requires an online machine of course.

Transmit the transaction to the network via:

ethereum-tool transmit -l http://localhost:8545 -f transaction

Check the status of the transaction via:

ethereum-tool confirm -l http://localhost:8545 -f transaction


Build the project via Maven:

mvn clean install

We use Netbeans as IDE. If you send pull requests, please keep the code clean to ease the review process.

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