eth-crypto

eth-crypto

Cryptographic javascript-functions for ethereum and how to use them together with web3 and solidity.

Tutorials

Creating Keys and use them for ethereum-transactions

In this tutorial we will create an ethereum-identity and use it so send transactions to the blockchain. Creating transactions.

Sign and validate data with solidity

In this tutorial we will sign data in javascript and validate the signature inside of a smart-contract. Signed Data.

Sending encrypted and signed data to other identites

Functions

Install

  npm install eth-crypto --save

// es6
import EthCrypto from 'eth-crypto';

// node
const EthCrypto = require('eth-crypto');

API

createIdentity()

Creates a new ethereum-identity with privateKey, publicKey and address as hex-string.

  const identity = EthCrypto.createIdentity();
  /* > {
      address: '0x3f243FdacE01Cfd9719f7359c94BA11361f32471',
      privateKey: '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07',
      publicKey: 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'
  } */

publicKeyByPrivateKey()

Derives the publicKey from a privateKey and returns it as hex-string.

  const publicKey = EthCrypto.publicKeyByPrivateKey(
      '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07'
  );
  // > 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'

addressByPublicKey()

Derives the ethereum-address from the publicKey.

  const address = EthCrypto.publicKeyToAddress(
      'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'
  );
  // > '0x3f243FdacE01Cfd9719f7359c94BA11361f32471'

sign()

Signs the message with the privateKey. Returns the signature as object with hex-strings.

  const signature = EthCrypto.sign(
      '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07', // privateKey
      'foobar' // message
  );
  /* > {
        v: '0x1b',
        r: '0xc04b809d8f33c46ff80c44ba58e866ff0d5126d9943b58bee03cc5279450cacc',
        s: '0x757a3393b695ba83b2aba0c35c150399bf7959493aad80d51d917435b1a7ebda'
    } */

recover()

Recovers the signers address from the signature.

    const signer = EthCrypto.recover(
      {
          v: '0x1b',
          r: '0xc04b809d8f33c46ff80c44ba58e866ff0d5126d9943b58bee03cc5279450cacc',
          s: '0x757a3393b695ba83b2aba0c35c150399bf7959493aad80d51d917435b1a7ebda'
      }, // signature
      'foobar' // signed message
  );
  // > '0x3f243FdacE01Cfd9719f7359c94BA11361f32471'

encryptWithPublicKey()

Encrypts the message with the publicKey so that only the corresponding privateKey can decrypt it. Returns (async) the encrypted data as object with hex-strings.

    const encrypted = await EthCrypto.encryptWithPublicKey(
        'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...', // publicKey
        'foobar' // message
    );
    /* >  {
            iv: '02aeac54cb45283b427bd1a5028552c1',
            ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',
            ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',
            mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'
        } */

decryptWithPrivateKey()

Decrypts the encrypted data with the privateKey. Returns (async) the message as string.

    const message = await EthCrypto.decryptWithPrivateKey(
        '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07', // privateKey
        {
            iv: '02aeac54cb45283b427bd1a5028552c1',
            ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',
            ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',
            mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'
        } // encrypted-data
    );
    // 'foobar'

signTransaction()

Signs a raw transaction with the privateKey. Returns a serialized tx which can be submitted to the node.

const identity = EthCrypto.createIdentity();
const rawTx = {
    from: identity.address,
    to: '0x86Fa049857E0209aa7D9e616F7eb3b3B78ECfdb0',
    value: 1000000000000000000,
    gasPrice: 5000000000,
    nonce: 0,
    gasLimit: 21000
};
const signedTx = EthCrypto.signTransaction(
    rawTx,
    identity.privateKey
);
console.log(signedTx);
// > '071d3a2040a2d2cb...'

// you can now send the tx to the node
const receipt = await web3.eth.sendSignedTransaction(signedTx);

txDataByCompiled()

Creates the data-string which must be submitted with an transaction to create a contract-instance.

const solc = require('solc');

// create compiled solidity-code
const compiled = solc.compile(
    'contract ExampleContract {...',
    1
).contracts[':ExampleContract'];

const createCode = EthCrypto.txDataByCompiled(
    compiled.interface, // abi
    compiled.bytecode, // bytecode
    [identity.address] // constructor-arguments
);

// now you can submit this to the blockchain
const serializedTx = EthCrypto.signTransaction(
    {
        from: identity.address,
        nonce: 0,
        gasLimit: 5000000,
        gasPrice: 5000000000,
        data: createCode
    },
    identity.privateKey
);
const receipt = await web3.eth.sendSignedTransaction(serializedTx);