ecurve
JavaScript component for Elliptic Curve Cryptography. Works in Node.js and the browser.
Package Info
- github: https://github.com/cryptocoinjs/ecurve
- tests: https://github.com/cryptocoinjs/ecurve/tree/master/test
- issues: https://github.com/cryptocoinjs/ecurve/issues
- license: MIT
- versioning: http://semver-ftw.org
Usage
Installation
npm install --save ecurve
Examples
The ecurve module works closely with the [bigi](http://cryptocoinjs.com/modules/misc/bigi/)(BigInteger) module. So it may useful to
require it in your code.
Get ECParams object:
var ecurve = require('ecurve')
var ecparams = ecurve.getCurveByName('secp256k1')
console.log(ecparams.n.toString(16))
// => fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141
console.log(ecparams.G.getEncoded().toString('hex')) //getEncoded() returns type 'Buffer' instead of 'BigInteger'
// => 0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798
console.log(ecparams.h.toString(16))
// => 1
Computing Bitcoin Address from Private Key:
var crypto = require('crypto')
var BigInteger = require('bigi') //npm install --save bigi@1.1.0
var ecurve = require('ecurve') //npm install --save ecurve@1.0.0
var cs = require('coinstring') //npm install --save coinstring@2.0.0
var privateKey = new Buffer("1184cd2cdd640ca42cfc3a091c51d549b2f016d454b2774019c2b2d2e08529fd", 'hex')
var ecparams = ecurve.getCurveByName('secp256k1')
var curvePt = ecparams.G.multiply(BigInteger.fromBuffer(privateKey))
var x = curvePt.affineX.toBuffer(32)
var y = curvePt.affineY.toBuffer(32)
var publicKey = Buffer.concat([new Buffer([0x04]), x, y])
console.log(publicKey.toString('hex'))
// => 04d0988bfa799f7d7ef9ab3de97ef481cd0f75d2367ad456607647edde665d6f6fbdd594388756a7beaf73b4822bc22d36e9bda7db82df2b8b623673eefc0b7495
//alternatively
publicKey = curvePt.getEncoded(false) //false forces uncompressed public key
console.log(publicKey.toString('hex'))
// => 04d0988bfa799f7d7ef9ab3de97ef481cd0f75d2367ad456607647edde665d6f6fbdd594388756a7beaf73b4822bc22d36e9bda7db82df2b8b623673eefc0b7495
//want compressed?
publicKey = curvePt.getEncoded(true) //true forces compressed public key
console.log(publicKey.toString('hex'))
// => 03d0988bfa799f7d7ef9ab3de97ef481cd0f75d2367ad456607647edde665d6f6f
var sha = crypto.createHash('sha256').update(publicKey).digest()
var pubkeyHash = crypto.createHash('rmd160').update(sha).digest()
// pubkeyHash of compressed public key
console.log(pubkeyHash.toString('hex'))
// => a1c2f92a9dacbd2991c3897724a93f338e44bdc1
// address of compressed public key
console.log(cs.encode(pubkeyHash, 0x0)) //<-- 0x0 is for public addresses
// => 1FkKMsKNJqWSDvTvETqcCeHcUQQ64kSC6s
console.log(cs.encode(privateKey, 0x80)) //<--- 0x80 is for private addresses
// => 5Hx15HFGyep2CfPxsJKe2fXJsCVn5DEiyoeGGF6JZjGbTRnqfiD
console.log(cs.encode(Buffer.concat([privateKey, new Buffer([0])]), 0x80)) // <-- compressed private address
// => KwomKti1X3tYJUUMb1TGSM2mrZk1wb1aHisUNHCQXTZq5aqzCxDY
Package CoinKey conveniently does the aforementioned example for you.
API
ecurve exports the following:
getCurveByName(curveString)
Use this to get the Bitcoin (all crypto currencies as well) curve parameters: secp256k1.
Does not support secp224r1 anymore.