1// Copyright 2012 The Chromium OS Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef LIBWEAVE_THIRD_PARTY_CHROMIUM_P224_H_
6#define LIBWEAVE_THIRD_PARTY_CHROMIUM_P224_H_
7
8#include <stddef.h>
9#include <stdint.h>
10
11#include <string>
12
13#include "base/strings/string_piece.h"
14
15namespace crypto {
16
17// P224 implements an elliptic curve group, commonly known as P224 and defined
18// in FIPS 186-3, section D.2.2.
19namespace p224 {
20
21// An element of the field (ℤ/pℤ) is represented with 8, 28-bit limbs in
22// little endian order.
23typedef uint32_t FieldElement[8];
24
25struct Point {
26  // SetFromString the value of the point from the 56 byte, external
27  // representation. The external point representation is an (x, y) pair of a
28  // point on the curve. Each field element is represented as a big-endian
29  // number < p.
30  bool SetFromString(const base::StringPiece& in);
31
32  // ToString returns an external representation of the Point.
33  std::string ToString() const;
34
35  // An Point is represented in Jacobian form (x/z², y/z³).
36  FieldElement x, y, z;
37};
38
39// kScalarBytes is the number of bytes needed to represent an element of the
40// P224 field.
41static const size_t kScalarBytes = 28;
42
43// ScalarMult computes *out = in*scalar where scalar is a 28-byte, big-endian
44// number.
45void ScalarMult(const Point& in, const uint8_t* scalar, Point* out);
46
47// ScalarBaseMult computes *out = g*scalar where g is the base point of the
48// curve and scalar is a 28-byte, big-endian number.
49void ScalarBaseMult(const uint8_t* scalar, Point* out);
50
51// Add computes *out = a+b.
52void Add(const Point& a, const Point& b, Point* out);
53
54// Negate calculates out = -a;
55void Negate(const Point& a, Point* out);
56
57}  // namespace p224
58
59}  // namespace crypto
60
61#endif  // LIBWEAVE_THIRD_PARTY_CHROMIUM_P224_H_
62