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/*************************************************
* ElGamal Source File *
* (C) 1999-2006 The Botan Project *
*************************************************/
#include <botan/elgamal.h>
#include <botan/numthry.h>
#include <botan/keypair.h>
#include <botan/util.h>
namespace Botan {
/*************************************************
* ElGamal_PublicKey Constructor *
*************************************************/
ElGamal_PublicKey::ElGamal_PublicKey(const DL_Group& grp, const BigInt& y1)
{
group = grp;
y = y1;
X509_load_hook();
}
/*************************************************
* Algorithm Specific X.509 Initialization Code *
*************************************************/
void ElGamal_PublicKey::X509_load_hook()
{
core = ELG_Core(group, y);
check_loaded_public();
}
/*************************************************
* ElGamal Encryption Function *
*************************************************/
SecureVector<byte> ElGamal_PublicKey::encrypt(const byte in[],
u32bit length) const
{
BigInt k = random_integer(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(const DL_Group& grp)
{
group = grp;
x = random_integer(2 * dl_work_factor(group_p().bits()));
PKCS8_load_hook();
check_generated_private();
}
/*************************************************
* ElGamal_PrivateKey Constructor *
*************************************************/
ElGamal_PrivateKey::ElGamal_PrivateKey(const DL_Group& grp, const BigInt& x1,
const BigInt& y1)
{
group = grp;
y = y1;
x = x1;
PKCS8_load_hook();
check_loaded_private();
}
/*************************************************
* Algorithm Specific PKCS #8 Initialization Code *
*************************************************/
void ElGamal_PrivateKey::PKCS8_load_hook()
{
if(y == 0)
y = power_mod(group_g(), x, group_p());
core = ELG_Core(group, y, x);
}
/*************************************************
* 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(bool strong) const
{
if(!DL_Scheme_PrivateKey::check_key(strong))
return false;
if(!strong)
return true;
try {
KeyPair::check_key(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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