ECIES (Browser)

browser.js

@@ -13,6 +13,8 @@
 var EC = require("elliptic").ec;
 
 var ec = new EC("secp256k1");
+// TODO(Kagami): Try to support IE11.
+var subtle = window.crypto.subtle || window.crypto.webkitSubtle;
 
 function assert(condition, message) {
   if (!condition) {
@@ -20,9 +22,54 @@ function assert(condition, message) {
   }
 }
 
-exports.getPublic = function(privateKey) {
+function randomBytes(size) {
+  var arr = new Uint8Array(size);
+  window.crypto.getRandomValues(arr);
+  return new Buffer(arr);
+}
+
+function sha512(msg) {
+  return subtle.digest({name: "SHA-512"}, msg).then(function(hash) {
+    return new Buffer(new Uint8Array(hash));
+  });
+}
+
+function getAes(op) {
+  return function(iv, key, msg) {
+    var importAlgorithm = {name: "AES-CBC"};
+    var keyp = subtle.importKey("raw", key, importAlgorithm, false, [op]);
+    return keyp.then(function(cryptoKey) {
+      var encAlgorithm = {name: "AES-CBC", iv: iv};
+      return subtle[op](encAlgorithm, cryptoKey, msg);
+    }).then(function(cipherText) {
+      return new Buffer(new Uint8Array(cipherText));
+    });
+  };
+}
+
+var aesCbcEncrypt = getAes("encrypt");
+var aesCbcDecrypt = getAes("decrypt");
+
+function hmacSha256Sign(key, msg) {
+  var algorithm = {name: "HMAC", hash: {name: "SHA-256"}};
+  var keyp = subtle.importKey("raw", key, algorithm, false, ["sign"]);
+  return keyp.then(function(cryptoKey) {
+    return subtle.sign(algorithm, cryptoKey, msg);
+  }).then(function(sig) {
+    return new Buffer(new Uint8Array(sig));
+  });
+}
+
+function hmacSha256Verify(key, msg, sig) {
+  var algorithm = {name: "HMAC", hash: {name: "SHA-256"}};
+  var keyp = subtle.importKey("raw", key, algorithm, false, ["verify"]);
+  return keyp.then(function(cryptoKey) {
+    return subtle.verify(algorithm, cryptoKey, sig, msg);
+  });
+}
+
+var getPublic = exports.getPublic = function(privateKey) {
   // This function has sync API so we throw an error immediately.
-  // (`elliptic` doesn't do this).
   assert(privateKey.length === 32, "Bad private key");
   // XXX(Kagami): `elliptic.utils.encode` returns array for every
   // encoding except `hex`.
@@ -31,23 +78,82 @@ exports.getPublic = function(privateKey) {
 
 exports.sign = function(privateKey, msg) {
   return new Promise(function(resolve) {
+    assert(privateKey.length === 32, "Bad private key");
     var key = ec.keyPair(privateKey);
     resolve(new Buffer(key.sign(msg).toDER()));
   });
 };
 
-exports.verify = function(key, msg, sig) {
+exports.verify = function(publicKey, msg, sig) {
   return new Promise(function(resolve, reject) {
-    key = ec.keyPair(key);
+    assert(publicKey.length === 65, "Bad public key");
+    assert(publicKey[0] === 4, "Bad public key");
+    var key = ec.keyPair(publicKey);
     return key.verify(msg, sig) ? resolve() : reject();
   });
 };
 
-exports.derive = function(privateKeyA, publicKeyB) {
+var derive = exports.derive = function(privateKeyA, publicKeyB) {
   return new Promise(function(resolve) {
+    assert(privateKeyA.length === 32, "Bad private key");
+    assert(publicKeyB.length === 65, "Bad public key");
+    assert(publicKeyB[0] === 4, "Bad public key");
     var keyA = ec.keyPair(privateKeyA);
     var keyB = ec.keyPair(publicKeyB);
     var Px = keyA.derive(keyB.getPublic());  // BN instance
-    resolve(new Buffer(Px.toString(16), "hex"));
+    resolve(new Buffer(Px.toString(16, 2), "hex"));
+  });
+};
+
+exports.encrypt = function(publicKeyTo, msg, opts) {
+  assert(subtle, "WebCryptoAPI is not supported");
+  opts = opts || {};
+  // Tmp variables to save context from flat promises;
+  var iv, ephemPublicKey, cipherText, macKey;
+  return new Promise(function(resolve) {
+    var ephemPrivateKey = opts.ephemPrivateKey || randomBytes(32);
+    ephemPublicKey = getPublic(ephemPrivateKey);
+    resolve(derive(ephemPrivateKey, publicKeyTo));
+  }).then(function(Px) {
+    return sha512(Px);
+  }).then(function(hash) {
+    iv = opts.iv || randomBytes(16);
+    var encryptionKey = hash.slice(0, 32);
+    macKey = hash.slice(32);
+    return aesCbcEncrypt(iv, encryptionKey, msg);
+  }).then(function(encrypted) {
+    cipherText = encrypted;
+    var dataToMac = Buffer.concat([iv, ephemPublicKey, cipherText]);
+    return hmacSha256Sign(macKey, dataToMac);
+  }).then(function(mac) {
+    return {
+      iv: iv,
+      ephemPublicKey: ephemPublicKey,
+      cipherText: cipherText,
+      mac: mac,
+    };
+  });
+};
+
+exports.decrypt = function(privateKey, opts) {
+  assert(subtle, "WebCryptoAPI is not supported");
+  // Tmp variables to save context from flat promises;
+  var encryptionKey;
+  return derive(privateKey, opts.ephemPublicKey).then(function(Px) {
+    return sha512(Px);
+  }).then(function(hash) {
+    encryptionKey = hash.slice(0, 32);
+    var macKey = hash.slice(32);
+    var dataToMac = Buffer.concat([
+      opts.iv,
+      opts.ephemPublicKey,
+      opts.cipherText
+    ]);
+    return hmacSha256Verify(macKey, dataToMac, opts.mac);
+  }).then(function(goodMac) {
+    assert(goodMac, "Bad MAC");
+    return aesCbcDecrypt(opts.iv, encryptionKey, opts.cipherText);
+  }).then(function(msg) {
+    return new Buffer(new Uint8Array(msg));
   });
 };

index.js

@@ -16,7 +16,7 @@ var secp256k1 = require("secp256k1");
  * @return {Buffer} A 65-byte public key.
  * @function
  */
-var getPublic = exports.getPublic = secp256k1.createPublicKey;
+exports.getPublic = secp256k1.createPublicKey;
 
 /**
  * Create an ECDSA signature.

package.json

@@ -34,6 +34,7 @@
   },
   "homepage": "https://github.com/bitchan/eccrypto",
   "devDependencies": {
+    "buffer-equal": "~0.0.1",
     "chai": "*",
     "jshint": "*",
     "karma": "^0.12.28",
@@ -46,7 +47,7 @@
     "mocha": "*"
   },
   "dependencies": {
-    "elliptic": "^1.0.0",
+    "elliptic": "^1.0.1",
     "es6-promise": "^2.0.1",
     "secp256k1": "~0.0.13"
   }

test.js

@@ -1,5 +1,6 @@
 var expect = require("chai").expect;
 var crypto = require("crypto");
+var bufferEqual = require("buffer-equal");
 var eccrypto = require("./");
 
 var msg = crypto.createHash("sha256").update("test").digest();
@@ -48,15 +49,22 @@ describe("ECDSA", function() {
   });
 
   it("should reject promise on invalid key when signing", function(done) {
-    eccrypto.sign(Buffer("test"), msg).catch(function() {
+    var k4 = Buffer("test");
+    var k192 = Buffer("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", "hex");
+    var k384 = Buffer("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb", "hex");
+    eccrypto.sign(k4, msg).catch(function() {
+      eccrypto.sign(k192, msg).catch(function() {
+        eccrypto.sign(k384, msg).catch(function() {
           done();
         });
       });
+    });
+  });
 
   it("should reject promise on invalid key when verifying", function(done) {
     eccrypto.sign(privateKey, msg).then(function(sig) {
       expect(Buffer.isBuffer(sig)).to.be.true;
-      eccrypto.verify(Buffer("test"), msg, sig).catch(function() {
+      eccrypto.verify(Buffer("test"), msg, sig).catch(function(e) {
         done();
       });
     });
@@ -74,6 +82,7 @@ describe("ECDSA", function() {
 });
 
 if (typeof window !== "undefined") {
+
 describe("ECDH", function() {
   it("should derive shared secret from privkey A and pubkey B", function() {
     return eccrypto.derive(privateKeyA, publicKeyB).then(function(Px) {
@@ -87,5 +96,99 @@ describe("ECDH", function() {
       });
     });
   });
+
+  it("should reject promise on bad keys", function(done) {
+    eccrypto.derive(Buffer("test"), publicKeyB).catch(function() {
+      eccrypto.derive(publicKeyB, publicKeyB).catch(function() {
+        eccrypto.derive(privateKeyA, privateKeyA).catch(function() {
+          eccrypto.derive(privateKeyB, Buffer("test")).catch(function() {
+            done();
+          });
+        });
+      });
+    });
+  });
 });
+
+describe("ECIES", function() {
+  var ephemPrivateKey = Buffer(32);
+  ephemPrivateKey.fill(4);
+  var ephemPublicKey = eccrypto.getPublic(ephemPrivateKey);
+  var iv = Buffer(16);
+  iv.fill(5);
+  var cipherText = Buffer("bbf3f0e7486b552b0e2ba9c4ca8c4579", "hex");
+  var mac = Buffer("dbb14a9b53dbd6b763dba24dc99520f570cdf8095a8571db4bf501b535fda1ed", "hex");
+  var encOpts = {ephemPrivateKey: ephemPrivateKey, iv: iv};
+  var decOpts = {iv: iv, ephemPublicKey: ephemPublicKey, cipherText: cipherText, mac: mac};
+
+  it("should encrypt", function() {
+    return eccrypto.encrypt(publicKeyB, Buffer("test"), encOpts)
+    .then(function(res) {
+      expect(bufferEqual(res.iv, iv)).to.be.true;
+      expect(bufferEqual(res.ephemPublicKey, ephemPublicKey)).to.be.true;
+      expect(bufferEqual(res.cipherText, cipherText)).to.be.true;
+      expect(bufferEqual(res.mac, mac)).to.be.true;
+    });
+  });
+
+  it("should decrypt", function() {
+    return eccrypto.decrypt(privateKeyB, decOpts)
+    .then(function(msg) {
+      expect(msg.toString()).to.equal("test");
+    });
+  });
+
+  it("should encrypt and decrypt", function() {
+    return eccrypto.encrypt(publicKeyA, Buffer("b to a")).then(function(res) {
+      return eccrypto.decrypt(privateKeyA, res);
+    }).then(function(msg) {
+      expect(msg.toString()).to.equal("b to a");
+    });
+  });
+
+  it("should reject promise on bad private key when decrypting", function(done) {
+    eccrypto.encrypt(publicKeyA, Buffer("test")).then(function(res) {
+      eccrypto.decrypt(privateKeyB, res).catch(function() {
+        done();
+      });
+    });
+  });
+
+  it("should reject promise on bad IV when decrypting", function(done) {
+    eccrypto.encrypt(publicKeyA, Buffer("test")).then(function(res) {
+      res.iv[0] ^= 1;
+      eccrypto.decrypt(privateKeyA, res).catch(function() {
+        done();
+      });
+    });
+  });
+
+  it("should reject promise on bad R when decrypting", function(done) {
+    eccrypto.encrypt(publicKeyA, Buffer("test")).then(function(res) {
+      res.ephemPublicKey[0] ^= 1;
+      eccrypto.decrypt(privateKeyA, res).catch(function() {
+        done();
+      });
+    });
+  });
+
+  it("should reject promise on bad cipher text when decrypting", function(done) {
+    eccrypto.encrypt(publicKeyA, Buffer("test")).then(function(res) {
+      res.cipherText[0] ^= 1;
+      eccrypto.decrypt(privateKeyA, res).catch(function() {
+        done();
+      });
+    });
+  });
+
+  it("should reject promise on bad MAC when decrypting", function(done) {
+    eccrypto.encrypt(publicKeyA, Buffer("test")).then(function(res) {
+      res.mac[0] ^= 1;
+      eccrypto.decrypt(privateKeyA, res).catch(function() {
+        done();
+      });
+    });
+  });
+});
+
 }