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_ 61