integration tests: add stealth address example

test/integration/darkwallet.js

@@ -0,0 +1,39 @@
+var assert = require('assert')
+
+var bigi = require('bigi')
+var bitcoin = require('../../')
+
+describe('bitcoinjs-lib (darkwallet examples)', function() {
+  it('can generate a single-key stealth address', function() {
+    var receiver = bitcoin.ECKey.fromWIF('5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss')
+    var sender = bitcoin.ECKey.fromWIF('Kxr9tQED9H44gCmp6HAdmemAzU3n84H3dGkuWTKvE23JgHMW8gct') // XXX: ephemeral, must be random to preserve privacy
+
+    var G = bitcoin.ECKey.curve.G
+    var d = receiver.d // secret (receiver only)
+    var Q = receiver.pub.Q // shared
+
+    var e = sender.d // secret (sender only)
+    var P = sender.pub.Q // shared
+
+    // derived shared secret
+    var eQ = Q.multiply(e) // sender
+    var dP = P.multiply(d) // receiver
+    assert.deepEqual(eQ.getEncoded(), dP.getEncoded())
+
+    var c = bigi.fromBuffer(bitcoin.crypto.sha256(eQ.getEncoded()))
+    var cG = G.multiply(c)
+
+    // derived public key
+    var QprimeS = Q.add(cG)
+    var QprimeR = G.multiply(d.add(c))
+    assert.deepEqual(QprimeR.getEncoded(), QprimeS.getEncoded())
+
+    // derived shared-secret address
+    var address = new bitcoin.ECPubKey(QprimeS).getAddress().toString()
+
+    assert.equal(address, '1EwCNJNZM5q58YPPTnjR1H5BvYRNeyZi47')
+  })
+
+  // TODO
+  it.skip('can generate a dual-key stealth address', function() {})
+})