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ethlightjs

README.md

EthLightJs

A minimal ethereum javascript wallet.

Get Started

git clone https://github.com/ConsenSys/LightWallet.git
cd LightWallet
npm install
npm run build-js

This will create the file ethlightjs.min.js that can be included in an HTML page:

<html>
  <body>
    <script src="ethlightjs.min.js"></script>
  </body>
</html>

To build a node package:

npm install path/to/LightWallet

To create a keystore, and sign and send a transaction:

keystore Function definitions

These are the interface functions for the keystore object. The keystore object holds a 12-word seed according to BIP39 spec. From this seed you can generate addresses and private keys, and use the private keys to sign transactions.

Note: Addresses and RLP encoded data are in the form of hex-strings. Hex-strings do not start with 0x.

keystore(seed, password)

Constructor of the keystore object. The seed seed is encrypted with password and stored encrypted in the keystore.

Inputs

  • words: string defining a 12-word seed according to BIP39
  • password: password to encrypt the seed

keystore.generateRandomSeed()

Generates a string consisting of a random 12-word seed and returns it.

keystore.generateNewAddress(password)

Generates a new address/private key pair from the seed and stores them in the keystore. The private key is stored encrypted with the users password.

keystore.deserialize(serialized_keystore)

Takes a serialized keystore string serialized_keystore and returns a new keystore object.

keystore.serialize()

Serializes the current keystore object into a JSON-encoded string and returns that string.

keystore.getAddresses()

Returns a list of hex-string addresses currently stored in the keystore.

keystore.getSeed(password)

Given the password, decrypts and returns the users 12-word seed.

keystore.exportPrivateKey(address, password)

Given the password, decrypts and returns the private key corresponding to address. This should be done sparingly as the recommended practice is for the keystore to sign transactions using keystore.signTx, so there is normally no need to export private keys.

keystore.signTx(rawTx, password, signingAddress)

Signs a transaction with the private key corresponding to signingAddress

Inputs

  • rawTx: Hex-string defining an RLP-encoded raw transaction.
  • password: the users password (string)
  • fromAddress: hex-string defining the address to send the transaction from.

Return value

Hex-string corresponding to the RLP-encoded raw transaction.

txutils Function definitions

txutils.createContractTx(fromAddress, txObject)

Using the data in txObject, creates an RLP-encoded transaction that will create the contract with compiled bytecode defined by txObject.data. Also computes the address of the created contract.

Inputs

  • fromAddress: Address to send the transaction from
  • txObject.gasLimit: Gas limit
  • txObject.gasPrice: Gas price
  • txObject.value: Endowment (optional)
  • txObject.nonce: Nonce of fromAddress
  • txObject.data: Compiled code of the contract

Output

Object obj with fields

  • obj.tx: RLP encoded transaction (hex string)
  • obj.addr: Address of the created contract

txutils.functionTx(abi, functionName, args, txObject)

Creates a transaction calling a function with name functionName, with arguments args conforming to abi. The function is defined in a contract with address txObject.to.

Inputs

  • abi: Json-formatted ABI as returned from the solc compiler
  • functionName: string with the function name
  • args: Array with the arguments to the function
  • txObject.to: Address of the contract
  • txObject.gasLimit: Gas limit
  • txObject.gasPrice: Gas price
  • txObject.value: Value to send
  • txObject.nonce: Nonce of sending address

Output

RLP-encoded hex string defining the transaction.

txutils.valueTx(txObject)

Creates a transaction sending value to txObject.to.

Inputs

  • txObject.to: Address to send to
  • txObject.gasLimit: Gas limit
  • txObject.gasPrice: Gas price
  • txObject.value: Value to send
  • txObject.nonce: Nonce of sending address

Output

RLP-encoded hex string defining the transaction.

helpers Function definitions

These are helper functions for packaging up some of the functionality in the keystore and txutils. They create, sign and send a transaction using txutils and keystore.

They use an object blockchainApi that define the following functions:

  • blockchainApi.getNonce(address): Returns the nonce of an address
  • blockchainApi.getBalance(address): Returns the balance of an address
  • blockchainApi.injectTransaction(rawTx): Injects a signed transaction into the network

We include two APIs: web3api and blockappsapi with predefined functions calling either an ethereum client or the blockapps backend.

helpers.sendFunctionTx(abi, contractAddr, functionName, args, fromAddr, txObject, blockchainApi, keystore, password)

Creates, signs, and sends a transaction calling a function functionName conforming to abi of a contract at address contractAddr with arguments args. Returns the hash of the transaction. The abi is a JSON object specifying the ABI of the contract.

The object txObject contains the following optional arguments:

  • txObject.gasLimit: Gas limit
  • txObject.gasPrice: Gas price
  • txObject.value: Value to send in the function call
  • txObject.nonce: Nonce of fromAddress

If the arguments are not provided default values will be used.

helpers.sendCreateContractTx(bytecode, fromAddr, txObject, blockchainApi, keystore, password)

Signs and sends a transaction creating the contract with compiled code bytecode. The object txObject contains optional arguments as described in the helpers.sendFunctionTx() section. Returns the address of the newly created contract.

helpers.sendValueTx(fromAddr, toAddr, value, txObject, blockchainApi, keystore, password)

Signs and send a transaction sending value wei from fromAddr to toAddr. The object txObject contains the optional items in the helpers.sendFunctionTx() section, except txObject.value.

Examples

See the file example_usage.js for usage of keystore and txutils.

See the file example_helpers.js for using the helpers functions.

See the file example_web.html for an example of how to use the LightWallet functionality in the browser.

Tests

Run all tests:

npm run test
npm run coverage

License