eckey

eckey

JavaScript component for Elliptical curve cryptography for crypto currencies such as Bitcoin, Litecoin, Dogecoin, etc.

Why?

This module provides a convenient way to compute relevant crypto currency operations that adhere to elliptical curve cryptography. To really understand how private keys, public keys, addresses, and how elliptical curve cryptography works with JavaScript, read this: http://procbits.com/2013/08/27/generating-a-bitcoin-address-with-javascript

Installation

npm install --save eckey

Usage

API

ECKey([bytes], [compressed])

Constructor function.

• bytes: The private key bytes. Must be 32 bytes in length. Should be an Array, Uint8Array, or a Buffer.
• compressed: Specify whether the key should be compressed or not.

var ECKey = require('eckey');
var secureRandom = require('secure-random'); 

var bytes = secureRandom(32); //https://github.com/jprichardson/secure-random
var key1 = new ECKey(bytes);
var key2 = ECKey(bytes); //<--- can also use without "new"
var compressedKey = new ECKey(bytes, true);

Note: Previous versions of this module would generate a random array of bytes for you if you didn't pass as input any to the constructor. This behavior has been removed to remove complexity and to ensure that the random generation is done securely. In the past, it wasn't.

compressed

Get/set whether the point on the curve is compressed. Affects the output of the WIF (wallet import format) and the address.

privateKey

Get/set the private key. When setting, the type can be either an Array, Buffer, or Uint8Array. When getting, the type is always Buffer. Setting would be useful if you don't pass a private key to the constructor.

var ECKey = require('eckey');
var conv = require('binstring');

var privateKeyHex = "1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd";

var key = new ECKey(conv(privateKeyHex, {in: 'hex', out: 'buffer'}), false);
console.log(key.privatekey.toString('hex')); // => 1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd

var keyCompressed = ECKey(conv(privateKeyHex, {in: 'hex', out: 'buffer'}), true);

//nothing changes when compressed
console.log(key.privatekey.toString('hex')); // => 1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd

privateExportKey

Get the private key along with a byte for compression if compressed is true. i.e.

if compressed
  privateExportKey = privateKey + 0x01
else
  privateExportKey = privateKey

This is useful inconjunction with the package coinstring to generate Wallet Import Format keys.

var ECKey = require('eckey');
var conv = require('binstring');

var privateKeyHex = "1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd";

var key = new ECKey(conv(privateKeyHex, {in: 'hex', out: 'buffer'}), false);
console.log(key.privateExportKey.toString('hex')); // => 1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd

var keyCompressed = new ECKey(conv(privateKeyHex, {in: 'hex', out: 'buffer'}), true);

//notice the extra "01" at the end?
console.log(key.privateExportKey.toString('hex')); // => 1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd01

publicKey

Get the public key. The type is Buffer.

var ECKey = require('eckey');
var conv = require('binstring');

var privateKeyHex = "1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd";

var key = new ECKey(conv(privateKeyHex, {in: 'hex', out: 'buffer'}), false);
console.log(key.publickey.toString('hex')); 
// => 04d0988bfa799f7d7ef9ab3de97ef481cd0f75d2367ad456607647edde665d6f6fbdd594388756a7beaf73b4822bc22d36e9bda7db82df2b8b623673eefc0b7495

var keyCompressed = ECKey(conv(privateKeyHex, {in: 'hex', out: 'buffer'}), true);

console.log(key.publickey.toString('hex')); 
// => 03d0988bfa799f7d7ef9ab3de97ef481cd0f75d2367ad456607647edde665d6f6f

publicPoint

Get the Public Key Point on the Ellipitical Curve.

toString()

Returns the string representation of the private key.

var ECKey = require('eckey');
var conv = require('binstring');

var privateKeyHex = "1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd";
var key = new ECKey(conv(privateKeyHex, {in: 'hex', out: 'buffer'}), true);

console.log(key.toString()) // => 1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd

References

• http://procbits.com/2013/08/27/generating-a-bitcoin-address-with-javascript
• https://github.com/bitcoinjs/bitcoinjs-lib/blob/master/src/eckey.js
• https://github.com/vbuterin/bitcoinjs-lib/blob/master/src/eckey.js