1 // Copyright 2012 The Chromium OS 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 LIBWEAVE_THIRD_PARTY_CHROMIUM_P224_H_ 6 #define LIBWEAVE_THIRD_PARTY_CHROMIUM_P224_H_ 7 8 #include <stddef.h> 9 #include <stdint.h> 10 11 #include <string> 12 13 #include "base/strings/string_piece.h" 14 15 namespace crypto { 16 17 // P224 implements an elliptic curve group, commonly known as P224 and defined 18 // in FIPS 186-3, section D.2.2. 19 namespace p224 { 20 21 // An element of the field (/p) is represented with 8, 28-bit limbs in 22 // little endian order. 23 typedef uint32_t FieldElement[8]; 24 25 struct Point { 26 // SetFromString the value of the point from the 56 byte, external 27 // representation. The external point representation is an (x, y) pair of a 28 // point on the curve. Each field element is represented as a big-endian 29 // number < p. 30 bool SetFromString(const base::StringPiece& in); 31 32 // ToString returns an external representation of the Point. 33 std::string ToString() const; 34 35 // An Point is represented in Jacobian form (x/z, y/z). 36 FieldElement x, y, z; 37 }; 38 39 // kScalarBytes is the number of bytes needed to represent an element of the 40 // P224 field. 41 static const size_t kScalarBytes = 28; 42 43 // ScalarMult computes *out = in*scalar where scalar is a 28-byte, big-endian 44 // number. 45 void ScalarMult(const Point& in, const uint8_t* scalar, Point* out); 46 47 // ScalarBaseMult computes *out = g*scalar where g is the base point of the 48 // curve and scalar is a 28-byte, big-endian number. 49 void ScalarBaseMult(const uint8_t* scalar, Point* out); 50 51 // Add computes *out = a+b. 52 void Add(const Point& a, const Point& b, Point* out); 53 54 // Negate calculates out = -a; 55 void Negate(const Point& a, Point* out); 56 57 } // namespace p224 58 59 } // namespace crypto 60 61 #endif // LIBWEAVE_THIRD_PARTY_CHROMIUM_P224_H_ 62
