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.
10 #include "base/basictypes.h"
11 #include "base/strings/string_piece.h"
12 #include "crypto/crypto_export.h"
16 // P224 implements an elliptic curve group, commonly known as P224 and defined
17 // in FIPS 186-3, section D.2.2.
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];
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
29 bool SetFromString(const base::StringPiece
& in
);
31 // ToString returns an external representation of the Point.
32 std::string
ToString() const;
34 // An Point is represented in Jacobian form (x/z², y/z³).
38 // kScalarBytes is the number of bytes needed to represent an element of the
40 static const size_t kScalarBytes
= 28;
42 // ScalarMult computes *out = in*scalar where scalar is a 28-byte, big-endian
44 void CRYPTO_EXPORT
ScalarMult(const Point
& in
, const uint8
* scalar
, Point
* out
);
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
);
50 // Add computes *out = a+b.
51 void CRYPTO_EXPORT
Add(const Point
& a
, const Point
& b
, Point
* out
);
53 // Negate calculates out = -a;
54 void CRYPTO_EXPORT
Negate(const Point
& a
, Point
* out
);
60 #endif // CRYPTO_P224_H_