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/*
Copyright (C) 2000-2007 MySQL AB
Use is subject to license terms
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301 USA.
*/
/* dh.cpp implements Diffie-Hellman support
*/
#include "runtime.hpp"
#include "dh.hpp"
#include "asn.hpp"
#include <math.h>
namespace TaoCrypt {
namespace { // locals
unsigned int DiscreteLogWorkFactor(unsigned int n)
{
// assuming discrete log takes about the same time as factoring
if (n<5)
return 0;
else
return (unsigned int)(2.4 * pow((double)n, 1.0/3.0) *
pow(log(double(n)), 2.0/3.0) - 5);
}
} // namespace locals
// Generate a DH Key Pair
void DH::GenerateKeyPair(RandomNumberGenerator& rng, byte* priv, byte* pub)
{
GeneratePrivate(rng, priv);
GeneratePublic(priv, pub);
}
// Generate private value
void DH::GeneratePrivate(RandomNumberGenerator& rng, byte* priv)
{
Integer x(rng, Integer::One(), min(p_ - 1,
Integer::Power2(2*DiscreteLogWorkFactor(p_.BitCount())) ) );
x.Encode(priv, p_.ByteCount());
}
// Generate public value
void DH::GeneratePublic(const byte* priv, byte* pub)
{
const word32 bc(p_.ByteCount());
Integer x(priv, bc);
Integer y(a_exp_b_mod_c(g_, x, p_));
y.Encode(pub, bc);
}
// Generate Agreement
void DH::Agree(byte* agree, const byte* priv, const byte* otherPub, word32
otherSz)
{
const word32 bc(p_.ByteCount());
Integer x(priv, bc);
Integer y;
if (otherSz)
y.Decode(otherPub, otherSz);
else
y.Decode(otherPub, bc);
Integer z(a_exp_b_mod_c(y, x, p_));
z.Encode(agree, bc);
}
DH::DH(Source& source)
{
Initialize(source);
}
void DH::Initialize(Source& source)
{
DH_Decoder decoder(source);
decoder.Decode(*this);
}
} // namespace
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