add support for Dark Wallet-style addresses

These functions are prefixed DW which stands for Dark Wallet. The code for the
Dark Wallet address format can be found here:

https://github.com/darkwallet/darkwallet/blob/develop/js/util/stealth.js

Note that I deliberately support only the simplest possible format, which is
where there is only one payload pubkey and the prefix is blank. I should now go
back and replace my old toString, fromString, toBuffer, fromBuffer functions
with these Dark Wallet versions, since they are much more well-thought out than
mine.

lib/expmt/stealthaddress.js

@@ -2,6 +2,8 @@ var Stealthkey = require('./stealthkey');
 var Base58check = require('../base58check');
 var Pubkey = require('../pubkey');
 var KDF = require('../kdf');
+var BufferWriter = require('../bufferwriter');
+var BufferReader = require('../bufferreader');
 
 var StealthAddress = function StealthAddress(addrstr) {
   if (!(this instanceof StealthAddress))
@@ -20,6 +22,9 @@ var StealthAddress = function StealthAddress(addrstr) {
   }
 };
 
+StealthAddress.mainver = 42;
+StealthAddress.testver = 43;
+
 StealthAddress.prototype.set = function(obj) {
   this.payloadPubkey = obj.payloadPubkey || this.payloadPubkey;
   this.scanPubkey = obj.scanPubkey || this.scanPubkey;
@@ -56,6 +61,29 @@ StealthAddress.prototype.fromBuffer = function(buf) {
   return this;
 };
 
+StealthAddress.prototype.fromDWBuffer = function(buf) {
+  var parsed = StealthAddress.parseDWBuffer(buf);
+  if ((parsed.version !== StealthAddress.mainver) && (parsed.version !== StealthAddress.testver))
+    throw new Error('Invalid version');
+  if (parsed.options !== 0)
+    throw new Error('Invalid options');
+  if (!parsed.scanPubkey)
+    throw new Error('Invalid scanPubkey');
+  if (parsed.payloadPubkeys.length !== 1)
+    throw new Error('Must have exactly one payloadPubkey');
+  if (parsed.nSigs !== 1)
+    throw new Error('Must require exactly one signature');
+  if (parsed.prefix.toString() !== "")
+    throw new Error('Only blank prefixes supported');
+  this.scanPubkey = parsed.scanPubkey;
+  this.payloadPubkey = parsed.payloadPubkeys[0];
+  return this;
+};
+
+StealthAddress.prototype.fromDWString = function(str) {
+  return this.fromDWBuffer(Base58check(str).toBuffer());
+};
+
 StealthAddress.prototype.fromString = function(str) {
   var buf = Base58check.decode(str);
   this.fromBuffer(buf);
@@ -86,6 +114,27 @@ StealthAddress.prototype.toBuffer = function() {
   return Buffer.concat([pBuf, sBuf]);
 };
 
+StealthAddress.prototype.toDWBuffer = function(networkstr) {
+  if (networkstr === 'testnet')
+    var version = StealthAddress.testver;
+  else
+    var version = StealthAddress.mainver;
+  var bw = new BufferWriter();
+  bw.writeUInt8(version);
+  bw.writeUInt8(0); //options
+  bw.write(this.scanPubkey.toDER(true));
+  bw.writeUInt8(1); //number of payload keys - we only support 1 (not multisig)
+  bw.write(this.payloadPubkey.toDER(true));
+  bw.writeUInt8(1); //number of signatures - we only support 1 (not multisig)
+  bw.writeUInt8(0); //prefix length - we do not support prefix yet
+  var buf = bw.concat();
+  return buf;
+};
+
+StealthAddress.prototype.toDWString = function(networkstr) {
+  return Base58check(this.toDWBuffer(networkstr)).toString();
+};
+
 StealthAddress.prototype.toString = function() {
   var buf = this.toBuffer();
   var b58 = Base58check.encode(buf);
@@ -93,4 +142,20 @@ StealthAddress.prototype.toString = function() {
   return b58;
 };
 
+StealthAddress.parseDWBuffer = function(buf) {
+  var br = new BufferReader(buf);
+  var parsed = {};
+  parsed.version = br.readUInt8();
+  parsed.options = br.readUInt8();
+  parsed.scanPubkey = Pubkey().fromBuffer(br.read(33));
+  parsed.nPayloadPubkeys = br.readUInt8();
+  parsed.payloadPubkeys = [];
+  for (var i = 0; i < parsed.nPayloadPubkeys; i++)
+    parsed.payloadPubkeys.push(Pubkey().fromBuffer(br.read(33)));
+  parsed.nSigs = br.readUInt8();
+  parsed.nPrefix = br.readUInt8();
+  parsed.prefix = br.read(parsed.nPrefix / 8);
+  return parsed;
+};
+
 module.exports = StealthAddress;

test/stealthaddress.js

@@ -26,6 +26,7 @@ describe('StealthAddress', function() {
   senderKeypair.privkey2pubkey();
 
   var addressString = '9dDbC9FzZ74r8njQkXD6W27gtrxLiWaeFPHxeo1fynQRXPicqxVt7u95ozbwoVVMXyrzaHKN9owsteg63FgwDfrxWx82SAW';
+  var dwhex = '2a0002697763d7e9becb0c180083738c32c05b0e2fee26d6278020c06bbb04d5f66b32010362408459041e0473298af3824dbabe4d2b7f846825ed4d1c2e2c670c07cb275d0100';
 
   it('should make a new stealth address', function() {
     var sa = new StealthAddress();
@@ -69,6 +70,22 @@ describe('StealthAddress', function() {
 
   });
 
+  describe('#fromDWBuffer', function() {
+
+    it('should parse this DW buffer', function() {
+      StealthAddress().fromDWBuffer(new Buffer(dwhex, 'hex')).toDWBuffer().toString('hex').should.equal(dwhex);
+    });
+
+  });
+
+  describe('#fromDWString', function() {
+
+    it('should parse this DW buffer', function() {
+      StealthAddress().fromDWString(Base58check(new Buffer(dwhex, 'hex')).toString()).toDWBuffer().toString('hex').should.equal(dwhex);
+    });
+
+  });
+
   describe('#fromString', function() {
 
     it('should give a stealthkey address with the right pubkeys', function() {
@@ -126,6 +143,24 @@ describe('StealthAddress', function() {
 
   });
 
+  describe('#toDWBuffer', function() {
+    
+    it('should return this known address buffer', function() {
+      var buf = Base58check.decode(addressString);
+      StealthAddress().fromBuffer(buf).toDWBuffer().toString('hex').should.equal(dwhex);
+    });
+
+  });
+
+  describe('#toDWString', function() {
+    
+    it('should return this known address buffer', function() {
+      var buf = Base58check.decode(addressString);
+      StealthAddress().fromBuffer(buf).toDWString().should.equal(Base58check(new Buffer(dwhex, 'hex')).toString());
+    });
+
+  });
+
   describe('#toString', function() {
     
     it('should return this known address string', function() {
@@ -134,4 +169,20 @@ describe('StealthAddress', function() {
 
   });
 
+  describe('@parseDWBuffer', function() {
+
+    it('should parse this known DW buffer', function() {
+      var buf = new Buffer(dwhex, 'hex');
+      var parsed = StealthAddress.parseDWBuffer(buf);
+      parsed.version.should.equal(42);
+      parsed.options.should.equal(0);
+      parsed.scanPubkey.toString().should.equal('02697763d7e9becb0c180083738c32c05b0e2fee26d6278020c06bbb04d5f66b32');
+      parsed.nPayloadPubkeys.should.equal(1);
+      parsed.payloadPubkeys[0].toString().should.equal('0362408459041e0473298af3824dbabe4d2b7f846825ed4d1c2e2c670c07cb275d');
+      parsed.nSigs.should.equal(1);
+      parsed.prefix.toString().should.equal('');
+    });
+
+  });
+
 });