i2pd/Signature.cpp
2015-04-08 13:49:27 -04:00

54 lines
1.3 KiB
C++

#include <cryptopp/integer.h>
#include <cryptopp/eccrypto.h>
#include "Signature.h"
namespace i2p
{
namespace crypto
{
class Ed25519
{
public:
Ed25519 (): b(256)
{
q = CryptoPP::Integer::Power2 (255) - CryptoPP::Integer (19); // 2^255-19
l = CryptoPP::Integer::Power2 (252) + CryptoPP::Integer ("27742317777372353535851937790883648493");
// 2^252 + 27742317777372353535851937790883648493
d = CryptoPP::Integer (-121665) * CryptoPP::Integer (121666).InverseMod (q); // -121665/121666
}
private:
CryptoPP::ECP::Point Sum (const CryptoPP::ECP::Point& p1, const CryptoPP::ECP::Point& p2)
{
CryptoPP::Integer m = d*p1.x*p2.x*p1.y*p2.y,
x = a_times_b_mod_c (p1.x*p2.y + p2.x*p1.y, (CryptoPP::Integer::One() + m).InverseMod (q), q),
y = a_times_b_mod_c (p1.y*p2.y + p1.x*p2.x, (CryptoPP::Integer::One() - m).InverseMod (q), q);
return CryptoPP::ECP::Point {x, y};
}
CryptoPP::ECP::Point Mul (const CryptoPP::ECP::Point& p, const CryptoPP::Integer& e)
{
CryptoPP::ECP::Point res {0, 1};
if (!e.IsZero ())
{
auto bitCount = e.BitCount ();
for (int i = bitCount - 1; i >= 0; i--)
{
res = Sum (res, res);
if (e.GetBit (i)) res = Sum (res, p);
}
}
return res;
}
private:
CryptoPP::Integer b, q, l, d;
};
}
}