Add Diffie-Hellman support to crypto module

Fixes #573

doc/api/crypto.markdown

@@ -146,3 +146,58 @@ the PEM encoded certificate, and `signature`, which is the previously calculates
 signature for the data, in the `signature_format` which can be `'binary'`, `'hex'` or `'base64'`.
 
 Returns true or false depending on the validity of the signature for the data and public key.
+
+### crypto.createDiffieHellman(prime_length)
+
+Creates a Diffie-Hellman key exchange object and generates a prime of the
+given bit length. The generator used is `2`.
+
+### crypto.createDiffieHellman(prime, encoding='binary')
+
+Creates a Diffie-Hellman key exchange object using the supplied prime. The
+generator used is `2`. Encoding can be `'binary'`, `'hex'`, or `'base64'`.
+
+### diffieHellman.generateKeys(encoding='binary')
+
+Generates private and public Diffie-Hellman key values, and returns the
+public key in the specified encoding. This key should be transferred to the
+other party. Encoding can be `'binary'`, `'hex'`, or `'base64'`.
+
+### diffieHellman.computeSecret(other_public_key, input_encoding='binary', output_encoding=input_encoding)
+
+Computes the shared secret using `other_public_key` as the other party's
+public key and returns the computed shared secret. Supplied key is
+interpreted using specified `input_encoding`, and secret is encoded using
+specified `output_encoding`. Encodings can be `'binary'`, `'hex'`, or
+`'base64'`. If no output encoding is given, the input encoding is used as
+output encoding.
+
+### diffieHellman.getPrime(encoding='binary')
+
+Returns the Diffie-Hellman prime in the specified encoding, which can be
+`'binary'`, `'hex'`, or `'base64'`.
+
+### diffieHellman.getGenerator(encoding='binary')
+
+Returns the Diffie-Hellman prime in the specified encoding, which can be
+`'binary'`, `'hex'`, or `'base64'`.
+
+### diffieHellman.getPublicKey(encoding='binary')
+
+Returns the Diffie-Hellman public key in the specified encoding, which can
+be `'binary'`, `'hex'`, or `'base64'`.
+
+### diffieHellman.getPrivateKey(encoding='binary')
+
+Returns the Diffie-Hellman private key in the specified encoding, which can
+be `'binary'`, `'hex'`, or `'base64'`.
+
+### diffieHellman.setPublicKey(public_key, encoding='binary')
+
+Sets the Diffie-Hellman public key. Key encoding can be `'binary'`, `'hex'`,
+or `'base64'`.
+
+### diffieHellman.setPrivateKey(public_key, encoding='binary')
+
+Sets the Diffie-Hellman private key. Key encoding can be `'binary'`, `'hex'`, or `'base64'`.
+

lib/crypto.js

@@ -29,6 +29,7 @@ try {
   var Decipher = binding.Decipher;
   var Sign = binding.Sign;
   var Verify = binding.Verify;
+  var DiffieHellman = binding.DiffieHellman;
   var crypto = true;
 } catch (e) {
 
@@ -139,3 +140,15 @@ exports.Verify = Verify;
 exports.createVerify = function(algorithm) {
   return (new Verify).init(algorithm);
 };
+
+exports.DiffieHellman = DiffieHellman;
+exports.createDiffieHellman = function(size_or_key, enc) {
+  if (!size_or_key) {
+    return new DiffieHellman();
+  } else if (!enc) {
+    return new DiffieHellman(size_or_key);
+  } else {
+    return new DiffieHellman(size_or_key, enc);
+  }
+
+}