p224.h revision 59c5f4b0fb104e8e4806e4934a3d5d112ad695ab 
1// Copyright (c) 2012 The Chromium 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 CRYPTO_P224_H_
6#define CRYPTO_P224_H_
7
8#include <string>
9
10#include "base/basictypes.h"
11#include "base/strings/string_piece.h"
12#include "crypto/crypto_export.h"
13
14namespace crypto {
15
16// P224 implements an elliptic curve group, commonly known as P224 and defined
17// in FIPS 186-3, section D.2.2.
18namespace p224 {
19
20// An element of the field (ℤ/pℤ) is represented with 8, 28-bit limbs in
21// little endian order.
22typedef uint32 FieldElement[8];
23
24struct CRYPTO_EXPORT Point {
25  // SetFromString the value of the point from the 56 byte, external
26  // representation. The external point representation is an (x, y) pair of a
27  // point on the curve. Each field element is represented as a big-endian
28  // number < p.
29  bool SetFromString(const base::StringPiece& in);
30
31  // ToString returns an external representation of the Point.
32  std::string ToString() const;
33
34  // An Point is represented in Jacobian form (x/z², y/z³).
35  FieldElement x, y, z;
36};
37
38// kScalarBytes is the number of bytes needed to represent an element of the
39// P224 field.
40static const size_t kScalarBytes = 28;
41
42// ScalarMult computes *out = in*scalar where scalar is a 28-byte, big-endian
43// number.
44void CRYPTO_EXPORT ScalarMult(const Point& in, const uint8* scalar, Point* out);
45
46// ScalarBaseMult computes *out = g*scalar where g is the base point of the
47// curve and scalar is a 28-byte, big-endian number.
48void CRYPTO_EXPORT ScalarBaseMult(const uint8* scalar, Point* out);
49
50// Add computes *out = a+b.
51void CRYPTO_EXPORT Add(const Point& a, const Point& b, Point* out);
52
53// Negate calculates out = -a;
54void CRYPTO_EXPORT Negate(const Point& a, Point* out);
55
56}  // namespace p224
57
58}  // namespace crypto
59
60#endif  // CRYPTO_P224_H_
61