crypto/p224.h

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