tests: improved readability for stealth address code

test/integration/stealth.js

@@ -6,42 +6,67 @@ var bitcoin = require('../../')
 
 var ecurve = require('ecurve')
 var secp256k1 = ecurve.getCurveByName('secp256k1')
+var G = secp256k1.G
+var n = secp256k1.n
+
+// c = sha256: e * (d * G)
+// cQ = (d * G) + (c * G)
+function stealthSend (e, Q) {
+  var eQ = Q.multiply(e) // shared secret
+
+  var c = bigi.fromBuffer(bitcoin.crypto.sha256(eQ.getEncoded()))
+  var cG = G.multiply(c)
+
+  var cQ = new bitcoin.ECPair(null, Q.add(cG))
+
+  return cQ
+}
+
+// c = sha256: d * (e * G)
+// cQ = (d + c) * G
+function stealthReceive (d, eG) {
+  var eQ = eG.multiply(d) // shared secret
+
+  var c = bigi.fromBuffer(bitcoin.crypto.sha256(eQ.getEncoded()))
+  var cQ = new bitcoin.ECPair(d.add(c).mod(n))
+
+  return cQ
+}
 
 describe('bitcoinjs-lib (crypto)', function () {
   it('can generate a single-key stealth address', function () {
-    var G = secp256k1.G
+    // XXX: should be randomly generated, see next test for example
-    var n = secp256k1.n
+    var recipient = bitcoin.ECPair.fromWIF('5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss') // private to recipient
+    var nonce = bitcoin.ECPair.fromWIF('KxVqB96pxbw1pokzQrZkQbLfVBjjHFfp2mFfEp8wuEyGenLFJhM9') // private to sender
 
-    function stealthSend (Q) {
+    // ... recipient reveals public key (recipient.Q) to sender
-      var noncePair = bitcoin.ECPair.makeRandom()
+    var forSender = stealthSend(nonce.d, recipient.Q)
-      var e = noncePair.d
+    assert.equal(forSender.getAddress(), '1CcZWwCpACJL3AxqoDbwEt4JgDFuTHUspE')
-      var eQ = Q.multiply(e) // shared secret
+    assert.throws(function () { forSender.toWIF() }, /Error: Missing private key/)
-      var c = bigi.fromBuffer(bitcoin.crypto.sha256(eQ.getEncoded()))
-      var cG = G.multiply(c)
-      var Qprime = Q.add(cG)
 
-      return {
+    // ... sender reveals nonce public key (nonce.Q) to recipient
-        shared: new bitcoin.ECPair(null, Qprime),
+    var forRecipient = stealthReceive(recipient.d, nonce.Q)
-        nonce: noncePair.Q
+    assert.equal(forRecipient.getAddress(), '1CcZWwCpACJL3AxqoDbwEt4JgDFuTHUspE')
-      }
+    assert.equal(forRecipient.toWIF(), 'L1yjUN3oYyCXV3LcsBrmxCNTa62bZKWCybxVJMvqjMmmfDE8yk7n')
-    }
 
-    function stealthReceive (d, P) {
+    // sender and recipient, both derived same address
-      var dP = P.multiply(d) // shared secret
+    assert.equal(forSender.getAddress(), forRecipient.getAddress())
-      var c = bigi.fromBuffer(bitcoin.crypto.sha256(dP.getEncoded()))
+  })
-      return new bitcoin.ECPair(d.add(c).mod(n))
-    }
 
-    // receiver private key
+  it('can generate a single-key stealth address (randomly)', function () {
-    var receiver = bitcoin.ECPair.fromWIF('5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss')
+    var recipient = bitcoin.ECPair.makeRandom() // private to recipient
+    var nonce = bitcoin.ECPair.makeRandom() // private to sender
 
-    var stealthS = stealthSend(receiver.Q) // public, done by sender
+    // ... recipient reveals public key (recipient.Q) to sender
-    // ... sender now reveals nonce to receiver
+    var forSender = stealthSend(nonce.d, recipient.Q)
+    assert.throws(function () { forSender.toWIF() }, /Error: Missing private key/)
 
-    var stealthR = stealthReceive(receiver.d, stealthS.nonce) // private, done by receiver
+    // ... sender reveals nonce public key (nonce.Q) to recipient
+    var forRecipient = stealthReceive(recipient.d, nonce.Q)
+    assert.doesNotThrow(function () { forRecipient.toWIF() })
 
-    // and check that we derived both sides correctly
+    // sender and recipient, both derived same address
-    assert.equal(stealthS.shared.getAddress(), stealthR.getAddress())
+    assert.equal(forSender.getAddress(), forRecipient.getAddress())
   })
 
   // TODO