crypto: add simple P224 implementation.

This is intended to be the underlying group for an EKE implementation for
Remoting.

BUG=none
TEST=crypto_unittests

Review URL: http://codereview.chromium.org/8431007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@108866 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 56 insertions, 0 deletions

diff --git a/crypto/p224.h b/crypto/p224.h
new file mode 100644
index 0000000..58dc0f1
--- /dev/null
+++ b/crypto/p224.h
@@ -0,0 +1,56 @@
+// Copyright (c) 2011 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.
+
+#ifndef CRYPTO_P224_H_
+#define CRYPTO_P224_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/string_piece.h"
+
+namespace crypto {
+
+// P224 implements an elliptic curve group, commonly known as P224 and defined
+// in FIPS 186-3, section D.2.2.
+namespace p224 {
+
+// An element of the field (ℤ/pℤ) is represented with 8, 28-bit limbs in
+// little endian order.
+typedef uint32 FieldElement[8];
+
+struct Point {
+  // SetFromString the value of the point from the 56 byte, external
+  // representation. The external point representation is an (x, y) pair of a
+  // point on the curve. Each field element is represented as a big-endian
+  // number < p.
+  bool SetFromString(const base::StringPiece& in);
+
+  // ToString returns an external representation of the Point.
+  std::string ToString() const;
+
+  // An Point is represented in Jacobian form (x/z², y/z³).
+  FieldElement x, y, z;
+};
+
+// ScalarMult computes *out = in*scalar where scalar is a 28-byte, big-endian
+// number.
+void ScalarMult(const Point& in, const uint8* scalar, Point* out);
+
+// ScalarBaseMult computes *out = g*scalar where g is the base point of the
+// curve and scalar is a 28-byte, big-endian number.
+void ScalarBaseMult(const uint8* scalar, Point* out);
+
+// Add computes *out = a+b.
+void Add(const Point& a, const Point& b, Point* out);
+
+// Negate calculates out = -a;
+void Negate(const Point& a, Point* out);
+
+}  // namespace p224
+
+}  // namespace crypto
+
+#endif  // CRYPTO_P224_H_