From cc316e94555e6210d3582ac43fd71181ef78ddc9 Mon Sep 17 00:00:00 2001
From: "Ryan X. Charles" <ryan@bitpay.com>
Date: Thu, 28 Aug 2014 14:43:21 -0700
Subject: [PATCH] ECIES

---
 index.js           |  1 +
 lib/expmt/ecies.js | 52 ++++++++++++++++++++++++++++++++++++++++++++++
 test/test.ecies.js | 41 ++++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+)
 create mode 100644 lib/expmt/ecies.js
 create mode 100644 test/test.ecies.js

diff --git a/index.js b/index.js
index 097bf4b..18db7a0 100644
--- a/index.js
+++ b/index.js
@@ -24,6 +24,7 @@ bitcore.Signature = require('./lib/signature');
 bitcore.expmt = {};
 bitcore.expmt.AES = require('./lib/expmt/aes');
 bitcore.expmt.CBC = require('./lib/expmt/cbc');
+bitcore.expmt.ECIES = require('./lib/ecies');
 bitcore.expmt.SymEnc = require('./lib/expmt/symenc');
 bitcore.expmt.Stealth = require('./lib/expmt/stealth');
 
diff --git a/lib/expmt/ecies.js b/lib/expmt/ecies.js
new file mode 100644
index 0000000..b96cf2a
--- /dev/null
+++ b/lib/expmt/ecies.js
@@ -0,0 +1,52 @@
+var SymEnc = require('./symenc');
+var Key = require('../key');
+var Point = require('../point');
+var Hash = require('../hash');
+var Pubkey = require('../pubkey');
+
+// http://en.wikipedia.org/wiki/Integrated_Encryption_Scheme
+var ECIES = function ECIES() {
+  if (!(this instanceof ECIES))
+    return new ECIES();
+};
+
+ECIES.encrypt = function(messagebuf, tokey, fromkey, ivbuf) {
+  var r = fromkey.privkey.bn;
+  var R = fromkey.pubkey.point;
+  var Rpubkey = fromkey.pubkey;
+  var Rbuf = Rpubkey.toDER(true);
+  var KB = tokey.pubkey.point;
+  var P = KB.mul(r);
+  var S = P.getX();
+  var Sbuf = S.toBuffer({size: 32});
+  var kEkM = Hash.sha512(Sbuf);
+  var kE = kEkM.slice(0, 32);
+  var kM = kEkM.slice(32, 64);
+  var c = SymEnc.encryptCipherkey(messagebuf, kE, ivbuf);
+  var d = Hash.sha256hmac(c, kM);
+  var encbuf = Buffer.concat([Rbuf, c, d]);
+  return encbuf;
+};
+
+ECIES.decrypt = function(encbuf, tokey) {
+  var kB = tokey.privkey.bn;
+  var frompubkey = Pubkey().fromDER(encbuf.slice(0, 33));
+  var R = frompubkey.point;
+  var P = R.mul(kB);
+  if (P.eq(new Point()))
+    throw new Error('P equals 0');
+  var S = P.getX();
+  var Sbuf = S.toBuffer({size: 32});
+  var kEkM = Hash.sha512(Sbuf);
+  var kE = kEkM.slice(0, 32);
+  var kM = kEkM.slice(32, 64);
+  var c = encbuf.slice(33, encbuf.length - 32);
+  var d = encbuf.slice(encbuf.length - 32, encbuf.length);
+  var d2 = Hash.sha256hmac(c, kM);
+  if (d.toString('hex') !== d2.toString('hex'))
+    throw new Error('Invalid checksum');
+  var messagebuf = SymEnc.decryptCipherkey(c, kE);
+  return messagebuf;
+};
+
+module.exports = ECIES;
diff --git a/test/test.ecies.js b/test/test.ecies.js
new file mode 100644
index 0000000..4ee661b
--- /dev/null
+++ b/test/test.ecies.js
@@ -0,0 +1,41 @@
+var ECIES = require('../lib/expmt/ecies');
+var should = require('chai').should();
+var Key = require('../lib/key');
+var Hash = require('../lib/hash');
+
+describe('#ECIES', function() {
+  
+  it('should make a new ECIES object', function() {
+    var ecies = new ECIES();
+    should.exist(ecies);
+  });
+
+  it('should make a new ECIES object when called without "new"', function() {
+    var ecies = ECIES();
+    should.exist(ecies);
+  });
+
+  var fromkey = Key().fromRandom();
+  var tokey = Key().fromRandom();
+  var messagebuf = Hash.sha256(new Buffer('my message is the hash of this string'));
+
+  describe('@encrypt', function() {
+
+    it('should return a buffer', function() {
+      var encbuf = ECIES.encrypt(messagebuf, tokey, fromkey);
+      Buffer.isBuffer(encbuf).should.equal(true);
+    });
+
+  });
+
+  describe('@decrypt', function() {
+
+    it('should decrypt that which was encrypted', function() {
+      var encbuf = ECIES.encrypt(messagebuf, tokey, fromkey);
+      var messagebuf2 = ECIES.decrypt(encbuf, tokey);
+      messagebuf2.toString('hex').should.equal(messagebuf.toString('hex'));
+    });
+
+  });
+
+});