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/*************************************************
* ElGamal Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/elgamal.h>
#include <botan/numthry.h>
#include <botan/keypair.h>
#include <botan/util.h>
#include <botan/libstate.h>
namespace Botan {
/*************************************************
* ElGamal_PublicKey Constructor *
*************************************************/
ElGamal_PublicKey::ElGamal_PublicKey(const DL_Group& grp, const BigInt& y1)
{
group = grp;
y = y1;
X509_load_hook(global_state().prng_reference());
}
/*************************************************
* Algorithm Specific X.509 Initialization Code *
*************************************************/
void ElGamal_PublicKey::X509_load_hook(RandomNumberGenerator& rng)
{
core = ELG_Core(rng, group, y);
load_check(rng);
}
/*************************************************
* ElGamal Encryption Function *
*************************************************/
SecureVector<byte>
ElGamal_PublicKey::encrypt(const byte in[], u32bit length,
RandomNumberGenerator& rng) const
{
BigInt k(rng, 2 * dl_work_factor(group_p().bits()));
return core.encrypt(in, length, k);
}
/*************************************************
* Return the maximum input size in bits *
*************************************************/
u32bit ElGamal_PublicKey::max_input_bits() const
{
return (group_p().bits() - 1);
}
/*************************************************
* ElGamal_PrivateKey Constructor *
*************************************************/
ElGamal_PrivateKey::ElGamal_PrivateKey(RandomNumberGenerator& rng,
const DL_Group& grp,
const BigInt& x_arg)
{
group = grp;
x = x_arg;
if(x == 0)
{
x.randomize(rng, 2 * dl_work_factor(group_p().bits()));
PKCS8_load_hook(rng, true);
}
else
PKCS8_load_hook(rng, false);
}
/*************************************************
* Algorithm Specific PKCS #8 Initialization Code *
*************************************************/
void ElGamal_PrivateKey::PKCS8_load_hook(RandomNumberGenerator& rng,
bool generated)
{
if(y == 0)
y = power_mod(group_g(), x, group_p());
core = ELG_Core(rng, group, y, x);
if(generated)
gen_check(rng);
else
load_check(rng);
}
/*************************************************
* ElGamal Decryption Function *
*************************************************/
SecureVector<byte> ElGamal_PrivateKey::decrypt(const byte in[],
u32bit length) const
{
return core.decrypt(in, length);
}
/*************************************************
* Check Private ElGamal Parameters *
*************************************************/
bool ElGamal_PrivateKey::check_key(RandomNumberGenerator& rng,
bool strong) const
{
if(!DL_Scheme_PrivateKey::check_key(rng, strong))
return false;
if(!strong)
return true;
try
{
KeyPair::check_key(rng,
get_pk_encryptor(*this, "EME1(SHA-1)"),
get_pk_decryptor(*this, "EME1(SHA-1)")
);
}
catch(Self_Test_Failure)
{
return false;
}
return true;
}
}
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