/*

* ElGamal

* (C) 1999-2007,2023 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#ifndef BOTAN_ELGAMAL_H_

#define BOTAN_ELGAMAL_H_

#include <botan/pk_keys.h>

#include <memory>

namespace Botan {

class BigInt;

class DL_Group;

class DL_PublicKey;

class DL_PrivateKey;

/**

* ElGamal Public Key

*/

class BOTAN_PUBLIC_API(2, 0) ElGamal_PublicKey : public virtual Public_Key {

   public:

      bool supports_operation(PublicKeyOperation op) const override { return (op == PublicKeyOperation::Encryption); }

      /**

      * Load a public key from the ASN.1 encoding

      * @param alg_id the X.509 algorithm identifier

      * @param key_bits DER encoded public key bits

      */

      ElGamal_PublicKey(const AlgorithmIdentifier& alg_id, std::span<const uint8_t> key_bits);

      /**

      * Create a public key.

      * @param group the underlying DL group

      * @param y the public value y = g^x mod p

      */

      ElGamal_PublicKey(const DL_Group& group, const BigInt& y);

      AlgorithmIdentifier algorithm_identifier() const override;

      std::vector<uint8_t> public_key_bits() const override;

      bool check_key(RandomNumberGenerator& rng, bool strong) const override;

      size_t estimated_strength() const override;

      size_t key_length() const override;

      std::string algo_name() const override { return "ElGamal"; }

      const BigInt& get_int_field(std::string_view field) const override;

      std::unique_ptr<Private_Key> generate_another(RandomNumberGenerator& rng) const final;

      std::unique_ptr<PK_Ops::Encryption> create_encryption_op(RandomNumberGenerator& rng,

                                                               std::string_view params,

                                                               std::string_view provider) const override;

   private:

      friend class ElGamal_PrivateKey;

      ElGamal_PublicKey() = default;

      ElGamal_PublicKey(std::shared_ptr<const DL_PublicKey> key) : m_public_key(std::move(key)) {}

      std::shared_ptr<const DL_PublicKey> m_public_key;

};

/**

* ElGamal Private Key

*/

BOTAN_DIAGNOSTIC_PUSH

BOTAN_DIAGNOSTIC_IGNORE_INHERITED_VIA_DOMINANCE

class BOTAN_PUBLIC_API(2, 0) ElGamal_PrivateKey final : public ElGamal_PublicKey,

                                                        public virtual Private_Key {

   public:

      /**

      * Load a private key from the ASN.1 encoding

      * @param alg_id the X.509 algorithm identifier

      * @param key_bits DER encoded key bits in ANSI X9.42 format

      */

      ElGamal_PrivateKey(const AlgorithmIdentifier& alg_id, std::span<const uint8_t> key_bits);

      /**

      * Create a new random private key.

      * @param rng random number generator to use

      * @param group the group to be used in the key

      */

      ElGamal_PrivateKey(RandomNumberGenerator& rng, const DL_Group& group);

      /**

      * Load a private key from the integer encoding

      * @param group the group to be used in the key

      * @param private_key the key's secret value

      */

      ElGamal_PrivateKey(const DL_Group& group, const BigInt& private_key);

      bool check_key(RandomNumberGenerator& rng, bool) const override;

      std::unique_ptr<Public_Key> public_key() const override;

      secure_vector<uint8_t> private_key_bits() const override;

      secure_vector<uint8_t> raw_private_key_bits() const override;

      const BigInt& get_int_field(std::string_view field) const override;

      std::unique_ptr<PK_Ops::Decryption> create_decryption_op(RandomNumberGenerator& rng,

                                                               std::string_view params,

                                                               std::string_view provider) const override;

   private:

      std::shared_ptr<const DL_PrivateKey> m_private_key;

};

BOTAN_DIAGNOSTIC_POP

}  // namespace Botan

#endif