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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 <stddef.h>
9 #include <stdint.h>
10 
11 #include <string>
12 
13 #include "base/strings/string_piece.h"
14 #include "crypto/crypto_export.h"
15 
16 namespace crypto {
17 
18 // P224 implements an elliptic curve group, commonly known as P224 and defined
19 // in FIPS 186-3, section D.2.2.
20 namespace p224 {
21 
22 // An element of the field (ℤ/pℤ) is represented with 8, 28-bit limbs in
23 // little endian order.
24 typedef uint32_t FieldElement[8];
25 
26 struct CRYPTO_EXPORT Point {
27   // SetFromString the value of the point from the 56 byte, external
28   // representation. The external point representation is an (x, y) pair of a
29   // point on the curve. Each field element is represented as a big-endian
30   // number < p.
31   bool SetFromString(base::StringPiece in);
32 
33   // ToString returns an external representation of the Point.
34   std::string ToString() const;
35 
36   // An Point is represented in Jacobian form (x/z², y/z³).
37   FieldElement x, y, z;
38 };
39 
40 // kScalarBytes is the number of bytes needed to represent an element of the
41 // P224 field.
42 static const size_t kScalarBytes = 28;
43 
44 // ScalarMult computes *out = in*scalar where scalar is a 28-byte, big-endian
45 // number.
46 void CRYPTO_EXPORT ScalarMult(const Point& in,
47                               const uint8_t* scalar,
48                               Point* out);
49 
50 // ScalarBaseMult computes *out = g*scalar where g is the base point of the
51 // curve and scalar is a 28-byte, big-endian number.
52 void CRYPTO_EXPORT ScalarBaseMult(const uint8_t* scalar, Point* out);
53 
54 // Add computes *out = a+b.
55 void CRYPTO_EXPORT Add(const Point& a, const Point& b, Point* out);
56 
57 // Negate calculates out = -a;
58 void CRYPTO_EXPORT Negate(const Point& a, Point* out);
59 
60 }  // namespace p224
61 
62 }  // namespace crypto
63 
64 #endif  // CRYPTO_P224_H_
65