crypto/p224.h

   1 // Copyright (c) 2011 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 #pragma once
   8
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/string_piece.h"
  13 #include "crypto/crypto_export.h"
  14
  15 namespace crypto {
  16
  17 // P224 implements an elliptic curve group, commonly known as P224 and defined
  18 // in FIPS 186-3, section D.2.2.
  19 namespace p224 {
  20
  21 // An element of the field (ℤ/pℤ) is represented with 8, 28-bit limbs in
  22 // little endian order.
  23 typedef uint32 FieldElement[8];
  24
  25 struct CRYPTO_EXPORT 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.
  41 static const size_t kScalarBytes = 28;
  42
  43 // ScalarMult computes *out = in*scalar where scalar is a 28-byte, big-endian
  44 // number.
  45 void CRYPTO_EXPORT ScalarMult(const Point& in, const uint8* 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.
  49 void CRYPTO_EXPORT ScalarBaseMult(const uint8* scalar, Point* out);
  50
  51 // Add computes *out = a+b.
  52 void CRYPTO_EXPORT Add(const Point& a, const Point& b, Point* out);
  53
  54 // Negate calculates out = -a;
  55 void CRYPTO_EXPORT Negate(const Point& a, Point* out);
  56
  57 }  // namespace p224
  58
  59 }  // namespace crypto
  60
  61 #endif  // CRYPTO_P224_H_