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/*
* ElGamal
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#ifndef BOTAN_ELGAMAL_H__
#define BOTAN_ELGAMAL_H__
#include <botan/dl_algo.h>
#include <botan/numthry.h>
#include <botan/reducer.h>
#include <botan/blinding.h>
#include <botan/pk_ops.h>
namespace Botan {
/**
* ElGamal Public Key
*/
class BOTAN_DLL ElGamal_PublicKey : public virtual DL_Scheme_PublicKey
{
public:
std::string algo_name() const { return "ElGamal"; }
DL_Group::Format group_format() const { return DL_Group::ANSI_X9_42; }
size_t max_input_bits() const { return (group_p().bits() - 1); }
ElGamal_PublicKey(const AlgorithmIdentifier& alg_id,
const MemoryRegion<byte>& key_bits) :
DL_Scheme_PublicKey(alg_id, key_bits, DL_Group::ANSI_X9_42)
{}
ElGamal_PublicKey(const DL_Group& group, const BigInt& y);
protected:
ElGamal_PublicKey() {}
};
/**
* ElGamal Private Key
*/
class BOTAN_DLL ElGamal_PrivateKey : public ElGamal_PublicKey,
public virtual DL_Scheme_PrivateKey
{
public:
bool check_key(RandomNumberGenerator& rng, bool) const;
ElGamal_PrivateKey(const AlgorithmIdentifier& alg_id,
const MemoryRegion<byte>& key_bits,
RandomNumberGenerator& rng);
ElGamal_PrivateKey(RandomNumberGenerator& rng,
const DL_Group& group,
const BigInt& priv_key = 0);
};
/**
* ElGamal encryption operation
*/
class BOTAN_DLL ElGamal_Encryption_Operation : public PK_Ops::Encryption
{
public:
size_t max_input_bits() const { return mod_p.get_modulus().bits() - 1; }
ElGamal_Encryption_Operation(const ElGamal_PublicKey& key);
SecureVector<byte> encrypt(const byte msg[], size_t msg_len,
RandomNumberGenerator& rng);
private:
Fixed_Base_Power_Mod powermod_g_p, powermod_y_p;
Modular_Reducer mod_p;
};
/**
* ElGamal decryption operation
*/
class BOTAN_DLL ElGamal_Decryption_Operation : public PK_Ops::Decryption
{
public:
size_t max_input_bits() const { return mod_p.get_modulus().bits() - 1; }
ElGamal_Decryption_Operation(const ElGamal_PrivateKey& key);
SecureVector<byte> decrypt(const byte msg[], size_t msg_len);
private:
Fixed_Exponent_Power_Mod powermod_x_p;
Modular_Reducer mod_p;
Blinder blinder;
};
}
#endif
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