ECDH (Node)

.gitignore

@@ -1,2 +1,3 @@
 /node_modules/
 /npm-debug.log
+/build/

.npmignore

@@ -1,3 +1,4 @@
-.travis.yml
-.jshint*
-karma.conf.js
+/.travis.yml
+/.jshint*
+/karma.conf.js
+/build/

README.md

@@ -4,12 +4,7 @@ JavaScript Elliptic curve cryptography library for both browserify and node.
 
 ## Motivation
 
-There is currently no any isomorphic ECC library which provides ECDSA, ECDH and ECIES for both Node.js and Browser and uses the fastest libraries available (e.g. [secp256k1-node](https://github.com/wanderer/secp256k1-node) is much faster than other libraries but can be used only on Node.js). So `eccrypto` is an attempt to create one. Current goals:
-
-- [x] ~~Convert private key to public~~
-- [x] ~~ECDSA~~
-- [ ] ECDH
-- [ ] ECIES
+There is currently no any isomorphic ECC library which provides ECDSA, ECDH and ECIES for both Node.js and Browser and uses the fastest implementation available (e.g. [secp256k1-node](https://github.com/wanderer/secp256k1-node) is much faster than other libraries but can be used only on Node.js). So `eccrypto` is an attempt to create one.
 
 ## Implementation details
 
@@ -61,6 +56,19 @@ eccrypto.sign(privateKey, msg).then(function(sig) {
 ### ECDH
 
 ```js
+var crypto = require("crypto");
+var eccrypto = require("eccrypto");
+
+var privateKeyA = crypto.randomBytes(32);
+var publicKeyA = eccrypto.getPublic(privateKeyA);
+var privateKeyB = crypto.randomBytes(32);
+var publicKeyB = eccrypto.getPublic(privateKeyB);
+
+eccrypto.derive(privateKeyA, publicKeyB).then(function(sharedKey1) {
+  eccrypto.derive(privateKeyB, publicKeyA).then(function(sharedKey2) {
+    console.log("Both shared keys are equal:", sharedKey1, sharedKey2);
+  });
+});
 ```
 
 ### ECIES

binding.gyp

@@ -0,0 +1,61 @@
+{
+  "targets": [
+    {
+      "target_name": "ecdh",
+      "include_dirs": ["<!(node -e \"require('nan')\")"],
+      "cflags": ["-Wall", "-O2"],
+      "sources": ["ecdh.cc"],
+      "conditions": [
+        ["OS=='win'", {
+          "conditions": [
+            [
+              "target_arch=='x64'", {
+                "variables": {
+                  "openssl_root%": "C:/OpenSSL-Win64"
+                },
+              }, {
+                "variables": {
+                  "openssl_root%": "C:/OpenSSL-Win32"
+                }
+              }
+            ]
+          ],
+          "libraries": [
+            "-l<(openssl_root)/lib/libeay32.lib",
+          ],
+          "include_dirs": [
+            "<(openssl_root)/include",
+          ],
+        }, {
+          "conditions": [
+            [
+              "target_arch=='ia32'", {
+                "variables": {
+                  "openssl_config_path": "<(nodedir)/deps/openssl/config/piii"
+                }
+              }
+            ],
+            [
+              "target_arch=='x64'", {
+                "variables": {
+                  "openssl_config_path": "<(nodedir)/deps/openssl/config/k8"
+                },
+              }
+            ],
+            [
+              "target_arch=='arm'", {
+                "variables": {
+                  "openssl_config_path": "<(nodedir)/deps/openssl/config/arm"
+                }
+              }
+            ],
+          ],
+          "include_dirs": [
+            "<(nodedir)/deps/openssl/openssl/include",
+            "<(openssl_config_path)"
+          ]
+        }
+      ]]
+    }
+  ]
+}

ecdh.cc

@@ -0,0 +1,102 @@
+#include <node.h>
+#include <nan.h>
+#include <openssl/evp.h>
+#include <openssl/ec.h>
+
+#define PRIVKEY_SIZE 32
+#define PUBKEY_SIZE 65
+#define CHECK(cond) do { if (!(cond)) goto error; } while (0)
+
+using node::Buffer;
+using v8::Handle;
+using v8::FunctionTemplate;
+using v8::Object;
+using v8::String;
+
+int derive(const uint8_t* privkey_a, const uint8_t* pubkey_b, uint8_t* shared) {
+  int rc = -1;
+  int res;
+  BIGNUM* pkey_bn = NULL;
+  BIGNUM* peerkey_bn_x = NULL;
+  BIGNUM* peerkey_bn_y = NULL;
+  EC_KEY* pkey = NULL;
+  EC_KEY* peerkey = NULL;
+  EVP_PKEY* evp_pkey = NULL;
+  EVP_PKEY* evp_peerkey = NULL;
+  EVP_PKEY_CTX* ctx = NULL;
+  size_t shared_len = PRIVKEY_SIZE;
+
+  // Private key A.
+  CHECK((pkey_bn = BN_bin2bn(privkey_a, PRIVKEY_SIZE, NULL)) != NULL);
+  CHECK((pkey = EC_KEY_new_by_curve_name(NID_secp256k1)) != NULL);
+  CHECK(EC_KEY_set_private_key(pkey, pkey_bn) == 1);
+  CHECK((evp_pkey = EVP_PKEY_new()) != NULL);
+  CHECK(EVP_PKEY_set1_EC_KEY(evp_pkey, pkey) == 1);
+
+  // Public key B.
+  CHECK((peerkey_bn_x = BN_bin2bn(pubkey_b+1, PRIVKEY_SIZE, NULL)) != NULL);
+  CHECK((peerkey_bn_y = BN_bin2bn(pubkey_b+33, PRIVKEY_SIZE, NULL)) != NULL);
+  CHECK((peerkey = EC_KEY_new_by_curve_name(NID_secp256k1)) != NULL);
+  res = EC_KEY_set_public_key_affine_coordinates(peerkey,
+                                                 peerkey_bn_x,
+                                                 peerkey_bn_y);
+  CHECK(res == 1);
+  CHECK((evp_peerkey = EVP_PKEY_new()) != NULL);
+  CHECK(EVP_PKEY_set1_EC_KEY(evp_peerkey, peerkey) == 1);
+
+  // Derive shared secret.
+  CHECK((ctx = EVP_PKEY_CTX_new(evp_pkey, NULL)) != NULL);
+  CHECK(EVP_PKEY_derive_init(ctx) == 1);
+  CHECK(EVP_PKEY_derive_set_peer(ctx, evp_peerkey) == 1);
+  CHECK((EVP_PKEY_derive(ctx, shared, &shared_len)) == 1);
+  CHECK(shared_len == PRIVKEY_SIZE);
+
+  rc = 0;
+error:
+  EVP_PKEY_CTX_free(ctx);
+  EVP_PKEY_free(evp_peerkey);
+  EC_KEY_free(peerkey);
+  BN_free(peerkey_bn_y);
+  BN_free(peerkey_bn_x);
+  EVP_PKEY_free(evp_pkey);
+  EC_KEY_free(pkey);
+  BN_free(pkey_bn);
+  return rc;
+}
+
+NAN_METHOD(Derive) {
+  NanScope();
+
+  if (args.Length() != 2 ||
+      !args[0]->IsObject() ||  // privkey_a
+      !args[1]->IsObject()) {  // pubkey_b
+    return NanThrowError("Bad input");
+  }
+
+  char* privkey_a = Buffer::Data(args[0]->ToObject());
+  size_t privkey_a_len = Buffer::Length(args[0]->ToObject());
+  char* pubkey_b = Buffer::Data(args[1]->ToObject());
+  size_t pubkey_b_len = Buffer::Length(args[1]->ToObject());
+  if (privkey_a == NULL ||
+      privkey_a_len != PRIVKEY_SIZE ||
+      pubkey_b == NULL ||
+      pubkey_b_len != PUBKEY_SIZE ||
+      pubkey_b[0] != 4) {
+    return NanThrowError("Bad input");
+  }
+
+  uint8_t* shared = (uint8_t *)malloc(PRIVKEY_SIZE);
+  if (derive((uint8_t *)privkey_a, (uint8_t *)pubkey_b, shared)) {
+    free(shared);
+    return NanThrowError("Internal error");
+  }
+  NanReturnValue(NanBufferUse((char *)shared, PRIVKEY_SIZE));
+}
+
+void InitAll(Handle<Object> exports) {
+  exports->Set(
+      NanNew<String>("derive"),
+      NanNew<FunctionTemplate>(Derive)->GetFunction());
+}
+
+NODE_MODULE(ecdh, InitAll)

index.js

@@ -8,7 +8,10 @@
 var promise = typeof Promise === "undefined" ?
               require("es6-promise").Promise :
               Promise;
+// TODO(Kagami): We may fallback to pure JS implementation
+// (`browser.js`) if this modules are failed to load.
 var secp256k1 = require("secp256k1");
+var ecdh = require("./build/Release/ecdh");
 
 /**
  * Compute the public key for a given private key.
@@ -44,3 +47,16 @@ exports.verify = function(publicKey, msg, sig) {
     return secp256k1.verify(publicKey, msg, sig) === 1 ? resolve() : reject();
   });
 };
+
+/**
+ * Derive shared secret for given private and public keys.
+ * @param {Buffer} privateKeyA - Sender's private key
+ * @param {Buffer} publicKeyB - Recipient's public key
+ * @return {Promise.<Buffer>} A promise that resolves with the derived
+ * shared secret (Px) and rejects on bad key.
+ */
+exports.derive = function(privateKeyA, publicKeyB) {
+  return new promise(function(resolve) {
+    resolve(ecdh.derive(privateKeyA, publicKeyB));
+  });
+};

package.json

@@ -5,6 +5,7 @@
   "main": "index.js",
   "browser": "browser.js",
   "scripts": {
+    "install": "node-gyp rebuild || exit 0",
     "test": "mocha && xvfb-run -a karma start && jshint .",
     "m": "mocha",
     "k": "xvfb-run -a karma start",
@@ -49,6 +50,9 @@
   "dependencies": {
     "elliptic": "^1.0.1",
     "es6-promise": "^2.0.1",
+    "nan": "^1.4.1"
+  },
+  "optionalDependencies": {
     "secp256k1": "~0.0.13"
   }
 }

test.js

@@ -81,8 +81,6 @@ 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) {
@@ -92,7 +90,7 @@ describe("ECDH", function() {
       return eccrypto.derive(privateKeyB, publicKeyA).then(function(Px2) {
         expect(Buffer.isBuffer(Px2)).to.be.true;
         expect(Px2.length).to.equal(32);
-        expect(Px.toString("hex")).to.equal(Px2.toString("hex"));
+        expect(bufferEqual(Px, Px2)).to.be.true;
       });
     });
   });
@@ -110,6 +108,8 @@ describe("ECDH", function() {
   });
 });
 
+if (typeof window !== "undefined") {
+
 describe("ECIES", function() {
   var ephemPrivateKey = Buffer(32);
   ephemPrivateKey.fill(4);