StealthMessage

This code should be regarded as being a proof-of-concept, and needs more review
before being used in production code. At least one thing is guaranteed to
change, and that is the format of a stealth address.

index.js

@@ -28,8 +28,9 @@ bitcore.expmt.AES = require('./lib/expmt/aes');
 bitcore.expmt.AESCBC = require('./lib/expmt/aescbc');
 bitcore.expmt.CBC = require('./lib/expmt/cbc');
 bitcore.expmt.ECIES = require('./lib/expmt/ecies');
-bitcore.expmt.Stealthkey = require('./lib/expmt/stealthkey');
 bitcore.expmt.StealthAddress = require('./lib/expmt/stealthaddress');
+bitcore.expmt.Stealthkey = require('./lib/expmt/stealthkey');
+bitcore.expmt.StealthMessage = require('./lib/expmt/stealthmessage');
 
 //dependencies, subject to change
 bitcore.deps = {};

lib/expmt/stealthkey.js

@@ -60,12 +60,12 @@ Stealthkey.prototype.getReceiveKeypair = function(senderPubkey) {
   return key;
 };
 
-Stealthkey.prototype.isForMe = function(senderPubkey, myPossiblePubkeyhash) {
+Stealthkey.prototype.isForMe = function(senderPubkey, myPossiblePubkeyhashbuf) {
   var pubkey = this.getReceivePubkey(senderPubkey);
   var pubkeybuf = pubkey.toDER(true);
   var pubkeyhash = Hash.sha256ripemd160(pubkeybuf);
 
-  if (pubkeyhash.toString('hex') === myPossiblePubkeyhash.toString('hex'))
+  if (pubkeyhash.toString('hex') === myPossiblePubkeyhashbuf.toString('hex'))
     return true;
   else
     return false;

lib/expmt/stealthmessage.js

@@ -0,0 +1,85 @@
+var Stealthkey = require('./stealthkey');
+var StealthAddress = require('./stealthaddress');
+var ECIES = require('./ecies');
+var Message = require('../message');
+var Keypair = require('../keypair');
+var Address = require('../address');
+var Pubkey = require('../pubkey');
+
+var StealthMessage = function StealthMessage(obj) {
+  if (!(this instanceof StealthMessage))
+    return new StealthMessage(obj);
+  if (obj)
+    this.set(obj);
+};
+
+StealthMessage.prototype.set = function(obj) {
+  this.messagebuf = obj.messagebuf || this.messagebuf;
+  this.encbuf = obj.encbuf || this.encbuf;
+  this.toStealthAddress = obj.toStealthAddress || this.toStealthAddress;
+  this.toStealthkey = obj.toStealthkey || this.toStealthkey;
+  this.fromKeypair = obj.fromKeypair || this.fromKeypair;
+  this.receiveAddress = obj.receiveAddress || this.receiveAddress;
+  return this;
+};
+
+StealthMessage.encrypt = function(messagebuf, toStealthAddress, fromKeypair, ivbuf) {
+  var sm = StealthMessage().set({
+    messagebuf: messagebuf,
+    toStealthAddress: toStealthAddress,
+    fromKeypair: fromKeypair
+  });
+  sm.encrypt(ivbuf);
+  var buf = Buffer.concat([
+    sm.receiveAddress.hashbuf,
+    sm.fromKeypair.pubkey.toDER(true),
+    sm.encbuf
+  ]);
+  return buf;
+};
+
+StealthMessage.decrypt = function(buf, toStealthkey) {
+  var sm = StealthMessage().set({
+    toStealthkey: toStealthkey,
+    receiveAddress: Address().set({hashbuf: buf.slice(0, 20)}),
+    fromKeypair: Keypair().set({pubkey: Pubkey().fromDER(buf.slice(20, 20 + 33))}),
+    encbuf: buf.slice(20 + 33)
+  });
+  return sm.decrypt().messagebuf;
+};
+
+StealthMessage.isForMe = function(buf, toStealthkey) {
+  var sm = StealthMessage().set({
+    toStealthkey: toStealthkey,
+    receiveAddress: Address().set({hashbuf: buf.slice(0, 20)}),
+    fromKeypair: Keypair().set({pubkey: Pubkey().fromDER(buf.slice(20, 20 + 33))}),
+    encbuf: buf.slice(20 + 33)
+  });
+  return sm.isForMe();
+};
+
+StealthMessage.prototype.encrypt = function(ivbuf) {
+  if (!this.fromKeypair)
+    this.fromKeypair = Keypair().fromRandom();
+  var receivePubkey = this.toStealthAddress.getReceivePubkey(this.fromKeypair);
+  this.receiveAddress = Address().fromPubkey(receivePubkey);
+  this.encbuf = ECIES.encrypt(this.messagebuf, Keypair().set({pubkey: receivePubkey}), this.fromKeypair, ivbuf);
+  return this;
+};
+
+StealthMessage.prototype.decrypt = function() {
+  var receiveKeypair = this.toStealthkey.getReceiveKeypair(this.fromKeypair.pubkey);
+  this.messagebuf = ECIES.decrypt(this.encbuf, receiveKeypair);
+  return this;
+};
+
+StealthMessage.prototype.isForMe = function() {
+  var receivePubkey = this.toStealthkey.getReceivePubkey(this.fromKeypair.pubkey);
+  var receiveAddress = Address().fromPubkey(receivePubkey);
+  if (receiveAddress.toString('hex') === this.receiveAddress.toString('hex'))
+    return true;
+  else
+    return false;
+};
+
+module.exports = StealthMessage;

test/stealthmessage.js

@@ -0,0 +1,130 @@
+var StealthMessage = require('../lib/expmt/stealthmessage');
+var Stealthkey = require('../lib/expmt/stealthkey');
+var StealthAddress = require('../lib/expmt/stealthAddress');
+var KDF = require('../lib/kdf');
+var Hash = require('../lib/hash');
+var should = require('chai').should();
+var Address = require('../lib/address');
+
+describe('StealthMessage', function() {
+
+  var payloadKeypair = KDF.buf2keypair(new Buffer('key1'));
+  var scanKeypair = KDF.buf2keypair(new Buffer('key2'));
+  var fromKeypair = KDF.buf2keypair(new Buffer('key3'));
+  var enchex = 'f557994f16d0d628fa4fdb4ab3d7e0bc5f2754f20381c7831a20c7c9ec88dcf092ea3683261798ccda991ed65a3a54a036d8125dec0381c7831a20c7c9ec88dcf092ea3683261798ccda991ed65a3a54a036d8125dec9f86d081884c7d659a2feaa0c55ad01560ba2904d3bc8395b6c4a6f87648edb33db6a22170e5e26f340c7ba943169210234cd6a753ad13919b0ab7d678b47b5e7d63e452382de2c2590fb57ef048f7b3';
+  var encbuf = new Buffer(enchex, 'hex');
+  var ivbuf = Hash.sha256(new Buffer('test')).slice(0, 128 / 8);
+  var sk = Stealthkey().set({payloadKeypair: payloadKeypair, scanKeypair: scanKeypair});
+  var sa = StealthAddress().fromStealthkey(sk);
+  var messagebuf = new Buffer('this is my message');
+  
+  it('should make a new stealthmessage', function() {
+    var sm = new StealthMessage();
+    should.exist(sm);
+    sm = StealthMessage()
+    should.exist(sm);
+  });
+
+  it('should allow "set" style syntax', function() {
+    var encbuf = StealthMessage().set({
+      messagebuf: messagebuf,
+      toStealthAddress: sa
+    }).encrypt().encbuf;
+    should.exist(encbuf);
+    encbuf.length.should.equal(113);
+  });
+
+  describe('#set', function() {
+    
+    it('should set the messagebuf', function() {
+      var sm = StealthMessage().set({messagebuf: messagebuf});
+      should.exist(sm.messagebuf);
+    });
+
+  });
+
+  describe('@encrypt', function() {
+
+    it('should encrypt a message', function() {
+      var encbuf = StealthMessage.encrypt(messagebuf, sa);
+      encbuf.length.should.equal(166);
+    });
+
+    it('should encrypt a message with this fromKeypair and ivbuf the same each time', function() {
+      var encbuf = StealthMessage.encrypt(messagebuf, sa, fromKeypair, ivbuf);
+      encbuf.length.should.equal(166);
+      encbuf.toString('hex').should.equal(enchex);
+    });
+
+  });
+
+  describe('@decrypt', function() {
+
+    it('should decrypt this known message correctly', function() {
+      var messagebuf2 = StealthMessage.decrypt(encbuf, sk);
+      messagebuf2.toString('hex').should.equal(messagebuf.toString('hex'));
+    });
+
+  });
+
+  describe('@isForMe', function() {
+
+    it('should know that this message is for me', function() {
+      StealthMessage.isForMe(encbuf, sk).should.equal(true);
+    });
+
+  });
+
+  describe('#encrypt', function() {
+    
+    it('should encrypt this message', function() {
+      var sm = StealthMessage().set({
+        messagebuf: messagebuf,
+        toStealthAddress: sa,
+        fromKeypair: fromKeypair
+      });
+      sm.encrypt().encbuf.length.should.equal(113);
+    });
+
+  });
+
+  describe('#decrypt', function() {
+    
+    it('should decrypt that which was encrypted', function() {
+      var sm = StealthMessage().set({
+        messagebuf: messagebuf,
+        toStealthAddress: sa
+      }).encrypt();
+      var messagebuf2 = StealthMessage().set({
+        encbuf: sm.encbuf,
+        fromKeypair: sm.fromKeypair,
+        toStealthkey: sk
+      }).decrypt().messagebuf;
+      messagebuf2.toString('hex').should.equal(messagebuf.toString('hex'));
+    });
+
+  });
+
+  describe('#isForMe', function() {
+    
+    it('should know that this message is for me', function() {
+      StealthMessage().set({
+        encbuf: encbuf,
+        toStealthkey: sk,
+        fromKeypair: fromKeypair,
+        receiveAddress: Address().set({hashbuf: encbuf.slice(0, 20)})
+      }).isForMe().should.equal(true);
+    });
+
+    it('should know that this message is not for me', function() {
+      StealthMessage().set({
+        encbuf: encbuf,
+        toStealthkey: sk,
+        fromKeypair: fromKeypair,
+        receiveAddress: Address().set({hashbuf: encbuf.slice(0, 20)})
+      }).isForMe().should.equal(true);
+    });
+
+  });
+
+});