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/*
* Diffie-Hellman
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/dh.h>
#include <botan/numthry.h>
#include <botan/workfactor.h>
namespace Botan {
/*
* DH_PublicKey Constructor
*/
DH_PublicKey::DH_PublicKey(const DL_Group& grp, const BigInt& y1)
{
group = grp;
y = y1;
}
/*
* Return the public value for key agreement
*/
std::vector<byte> DH_PublicKey::public_value() const
{
return unlock(BigInt::encode_1363(y, group_p().bytes()));
}
/*
* Create a DH private key
*/
DH_PrivateKey::DH_PrivateKey(RandomNumberGenerator& rng,
const DL_Group& grp,
const BigInt& x_arg)
{
group = grp;
x = x_arg;
if(x == 0)
{
const BigInt& p = group_p();
x.randomize(rng, 2 * dl_work_factor(p.bits()));
}
if(y == 0)
y = power_mod(group_g(), x, group_p());
if(x == 0)
gen_check(rng);
else
load_check(rng);
}
/*
* Load a DH private key
*/
DH_PrivateKey::DH_PrivateKey(const AlgorithmIdentifier& alg_id,
const secure_vector<byte>& key_bits,
RandomNumberGenerator& rng) :
DL_Scheme_PrivateKey(alg_id, key_bits, DL_Group::ANSI_X9_42)
{
if(y == 0)
y = power_mod(group_g(), x, group_p());
load_check(rng);
}
/*
* Return the public value for key agreement
*/
std::vector<byte> DH_PrivateKey::public_value() const
{
return DH_PublicKey::public_value();
}
DH_KA_Operation::DH_KA_Operation(const DH_PrivateKey& dh,
RandomNumberGenerator& rng) :
p(dh.group_p()), powermod_x_p(dh.get_x(), p)
{
BigInt k(rng, p.bits() - 1);
blinder = Blinder(k, powermod_x_p(inverse_mod(k, p)), p);
}
secure_vector<byte> DH_KA_Operation::agree(const byte w[], size_t w_len)
{
BigInt input = BigInt::decode(w, w_len);
if(input <= 1 || input >= p - 1)
throw Invalid_Argument("DH agreement - invalid key provided");
BigInt r = blinder.unblind(powermod_x_p(blinder.blind(input)));
return BigInt::encode_1363(r, p.bytes());
}
}
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