Gem for creating and signing Ethereum transactions.
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se3000 Merge pull request #37 from se3000/bugs/fix-backwards-compatibility
rename default_chain_id back to chain_id
Latest commit 8da9832 Oct 10, 2018

Eth Travis-CI Code Climate Gitter

A simple library to build and sign Ethereum transactions. Allows separation of key and node management. Sign transactions and handle keys anywhere you can run ruby, broadcast transactions through any node.


Add this line to your application's Gemfile:

gem 'eth'

And then execute:

$ bundle

Or install it yourself as:

$ gem install eth



Create a new public/private key and get its address:

key =
key.address # EIP55 checksummed address

Import an existing key:

old_key = priv: private_key

Or decrypt an encrypted key:

decrypted_key = Eth::Key.decrypt'./some/path.json'), 'p455w0rD'

You can also encrypt your keys for use with other ethereum libraries:

encrypted_key_info = Eth::Key.encrypt key, 'p455w0rD'


Build a transaction from scratch:

tx ={
  data: hex_data,
  gas_limit: 21_000,
  gas_price: 3_141_592,
  nonce: 1,
  to: key2.address,
  value: 1_000_000_000_000,

Or decode an encoded raw transaction:

tx = Eth::Tx.decode hex

Then sign the transaction:

tx.sign key

Get the raw transaction with tx.hex, and broadcast it through any Ethereum node. Or, just get the TXID with tx.hash.


Validate an EIP55 checksummed address:

Eth::Utils.valid_address? address

Or add a checksum to an existing address:

Eth::Utils.format_address "0x4bc787699093f11316e819b5692be04a712c4e69" # => "0x4bc787699093f11316e819B5692be04A712C4E69"

Personal Signatures

You can recover public keys and generate web3/metamask-compatible signatures:

# Generate signature
key.personal_sign('hello world')

# Recover signature
message = 'test'
signature = '0x3eb24bd327df8c2b614c3f652ec86efe13aa721daf203820241c44861a26d37f2bffc6e03e68fc4c3d8d967054c9cb230ed34339b12ef89d512b42ae5bf8c2ae1c'
Eth::Key.personal_recover(message, signature) # => 043e5b33f0080491e21f9f5f7566de59a08faabf53edbc3c32aaacc438552b25fdde531f8d1053ced090e9879cbf2b0d1c054e4b25941dab9254d2070f39418afc


In order to prevent replay attacks, you must specify which Ethereum chain your transactions are created for. See EIP 155 for more detail.

Eth.configure do |config|
  config.chain_id = 1 # nil by default, meaning valid on any chain


Bug reports and pull requests are welcome on GitHub at Tests are encouraged.


First install the Ethereum common tests:

git submodule update --init

Then run the associated tests:



The gem is available as open source under the terms of the MIT License.


  • Better test suite.
  • Expose API for HD keys.
  • Support signing with libsecp256k1.