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/*
* Diffie-Hellman
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/pk_utils.h>
#include <botan/dh.h>
#include <botan/workfactor.h>
#include <botan/pow_mod.h>
#include <botan/blinding.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();
}
namespace {
/**
* DH operation
*/
class DH_KA_Operation : public PK_Ops::Key_Agreement
{
public:
typedef DH_PrivateKey Key_Type;
DH_KA_Operation(const DH_PrivateKey& key, const std::string&);
secure_vector<byte> agree(const byte w[], size_t w_len);
private:
const BigInt& m_p;
Fixed_Exponent_Power_Mod m_powermod_x_p;
Blinder m_blinder;
};
DH_KA_Operation::DH_KA_Operation(const DH_PrivateKey& dh, const std::string&) :
m_p(dh.group_p()),
m_powermod_x_p(dh.get_x(), m_p),
m_blinder(m_p,
[](const BigInt& k) { return k; },
[this](const BigInt& k) { return m_powermod_x_p(inverse_mod(k, m_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 >= m_p - 1)
throw Invalid_Argument("DH agreement - invalid key provided");
BigInt r = m_blinder.unblind(m_powermod_x_p(m_blinder.blind(input)));
return BigInt::encode_1363(r, m_p.bytes());
}
}
BOTAN_REGISTER_PK_KEY_AGREE_OP("DH", DH_KA_Operation);
}
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