StealthTx

For spotting transactions to which you have the stealth key (or at least the
scan key) and creating transactions to a stealth address. So far it is only
partially working - you can see if a transaction is a stealth transaction (or
at least one of a limited kind of stealth transactions), and you can see that
you do not have the stealth key to spend one of these transactions. However, I
have not yet tested whether you can see a stealth transaction that you actually
have the key to. Also, it is not yet easy to spend to a stealth address.

lib/expmt/stealthtx.js

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+var StealthAddress = require('./stealthaddress');
+var StealthKey = require('./stealthkey');
+var Transaction = require('../transaction');
+var Pubkey = require('../pubkey');
+
+var StealthTx = function StealthTx(tx, sa, sk) {
+  if (!(this instanceof StealthTx))
+    return new StealthTx(tx, sa, sk);
+  if (tx instanceof Transaction) {
+    this.tx = tx;
+    this.sa = sa;
+    this.sk = sk;
+  } else if (tx) {
+    var obj = tx;
+    this.set(obj);
+  }
+};
+
+StealthTx.prototype.set = function(obj) {
+  this.sk = obj.sk || this.sk;
+  this.sa = obj.sa || this.sa;
+  this.tx = obj.tx || this.tx;
+  return this;
+};
+
+StealthTx.prototype.isForMe = function() {
+  if (!this.notMine())
+    return true;
+  else
+    return false;
+};
+
+StealthTx.prototype.notMine = function() {
+  var err;
+  if (err = this.notStealth())
+    return "Not stealth: " + err;
+  var txopbuf = this.tx.txouts[0].script.chunks[1].buf;
+  var parsed = StealthTx.parseOpReturnData(txopbuf);
+  var pubkey = parsed.pubkey;
+  var pubkeyhashbuf = this.tx.txouts[1].script.chunks[2].buf;
+  var sk = this.sk;
+  if (sk.isForMe(pubkey, pubkeyhashbuf)) {
+    return false;
+  } else {
+    return "StealthTx not mine";
+  }
+};
+
+//For now, we only support a very limited variety of stealth tx
+StealthTx.prototype.notStealth = function() {
+  var txouts = this.tx.txouts;
+  if (!(txouts.length >= 2))
+    return "Not enough txouts";
+  if (!txouts[0].script.isOpReturn())
+    return "First txout is not OP_RETURN";
+  if (!txouts[1].script.isPubkeyhashOut())
+    return "Second txout is not pubkeyhash";
+  return false;
+};
+
+StealthTx.parseOpReturnData = function(buf) {
+  var parsed = {};
+  parsed.version = buf[0];
+  parsed.noncebuf = buf.slice(1, 5);
+  parsed.pubkey = Pubkey().fromBuffer(buf.slice(5, 5 + 33));
+  return parsed;
+};
+
+module.exports = StealthTx;

test/stealthtx.js

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+var should = require('chai').should();
+var Txout = require('../lib/txout');
+var Stealthkey = require('../lib/expmt/stealthkey');
+var StealthTx = require('../lib/expmt/stealthtx');
+var Transaction = require('../lib/transaction');
+var Varint = require('../lib/varint');
+
+describe('StealthTx', function() {
+  
+  var txhex = '0100000001c828ccce36eca04f96321ad488528af86c7598e67157c4f8e2f462a9e0e3af5f010000006a47304402204525eef6a56cc57fb184e53efdfdc1086d5265da21480d55c2184536440a64f70220349cdc6c66a8507dde0d172fe64aeb57ae56e014b50315f615086a6b85c5424e012102c0633ddb6bf2a8686e2ba4ce8026c94e1e27ef12e73f8fed6d6d2b97199f9b74ffffffff020000000000000000286a2606deadbeef0365b5a5b0ba059666e907b0b5e07b37fdb162d1399ed829315491fe1f30c87b3f905f0100000000001976a9142042d5e7ef9e82346419fbfe7df5ae52fe4bea3c88ac00000000';
+  var txbuf = new Buffer(txhex, 'hex');
+  var txidhex = '66da969fff214c329e27062beaf3baf20ed035801559b31f3e868c2de4cdfc5b';
+  var tx = Transaction(txbuf);
+
+  it('should make a new StealthTx', function() {
+    var stx = new StealthTx();
+    should.exist(stx);
+    stx = StealthTx();
+    should.exist(stx);
+  });
+
+  describe('#isForMe', function() {
+    
+    it('should return false for this known tx and random stealthkey', function() {
+      var sk = Stealthkey().fromRandom();
+      var stx = StealthTx().set({sk: sk, tx: tx});
+      stx.isForMe().should.equal(false);
+    });
+
+  });
+
+  describe('#notMine', function() {
+    
+    it('should return true for this known tx and random stealthkey', function() {
+      var sk = Stealthkey().fromRandom();
+      var stx = StealthTx().set({sk: sk, tx: tx});
+      stx.notMine().should.equal("StealthTx not mine");
+    });
+
+  });
+
+  describe('#notStealth', function() {
+
+    it('should know this is a stealth tx', function() {
+      var stx = StealthTx().set({tx: tx});
+      stx.notStealth().should.equal(false);
+    });
+
+    it('should know this is not a stealth tx', function() {
+      var tx2 = Transaction(tx);
+      tx2.txouts.pop();
+      tx2.txoutsvi = Varint(1);
+      var stx = StealthTx().set({tx: tx2});
+      stx.notStealth().should.equal("Not enough txouts");
+    });
+
+  });
+
+  describe('@parseOpReturnData', function() {
+    var txout = tx.txouts[0];
+    var buf = txout.script.chunks[1].buf;
+    var parsed = StealthTx.parseOpReturnData(buf);
+    (typeof parsed.version).should.equal('number');
+    parsed.noncebuf.length.should.be.above(0);
+    parsed.pubkey.toBuffer().length.should.equal(33);
+  });
+
+});