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| 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_ |
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