Added Curve25519-donna changes.

Added a wrapper class that implements the following API calls which for
Curve25519.
+ ScalarMult to compute the shared key.
+ ScalarBaseMult to get public key.
+ ConvertToPrivateKey returns a private key from random bytes.

Per agl/wtc, grabbed the rev 234205ff from the git repo
(https://github.com/agl/curve25519-donna/tree/234205ff1ecaf6b3c1dc76798a462c4293f31fdb)
and checked it in to crypto/ because that version has pure Google copyright.

R=wtc@chromium.org,agl@chromium.org,rsleevi@chromium.org
TEST=crypto unit tests

Review URL: https://chromiumcodereview.appspot.com/12457004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@187074 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 36 insertions, 0 deletions

diff --git a/crypto/curve25519.cc b/crypto/curve25519.cc
new file mode 100644
index 0000000..3346df9
--- /dev/null
+++ b/crypto/curve25519.cc
@@ -0,0 +1,36 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "crypto/curve25519.h"
+
+// Curve25519 is specified in terms of byte strings, not numbers, so all
+// implementations take and return the same sequence of bits. So the byte
+// order is implicitly specified as in, say, SHA1.
+//
+// Prototype for |curve25519_donna| function in
+// third_party/curve25519-donna/curve25519-donna.c
+extern "C" int curve25519_donna(uint8*, const uint8*, const uint8*);
+
+namespace crypto {
+
+namespace curve25519 {
+
+void ScalarMult(const uint8* private_key,
+                const uint8* peer_public_key,
+                uint8* shared_key) {
+  curve25519_donna(shared_key, private_key, peer_public_key);
+}
+
+// kBasePoint is the base point (generator) of the elliptic curve group.
+// It is little-endian version of '9' followed by 31 zeros.
+// See "Computing public keys" section of http://cr.yp.to/ecdh.html.
+static const unsigned char kBasePoint[32] = {9};
+
+void ScalarBaseMult(const uint8* private_key, uint8* public_key) {
+  curve25519_donna(public_key, private_key, kBasePoint);
+}
+
+}  // namespace curve25519
+
+}  // namespace crypto