/*-
 * Copyright (c) 2017-2024 Ribose Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef RNP_ELG_H_
#define RNP_ELG_H_

#include <stdint.h>
#include "crypto/rng.h"
#include "crypto/mpi.hpp"
#include "mem.h"

namespace pgp {
namespace eg {

class Signature {
  public:
    /* This is kept only for packet reading. Implementation MUST
     * not create elgamal signatures */
    mpi r{};
    mpi s{};
};

class Encrypted {
  public:
    mpi g;
    mpi m;
};

class Key {
  public:
    mpi p{};
    mpi g{};
    mpi y{};
    /* secret mpi */
    mpi x{};

    void
    clear_secret()
    {
        x.forget();
    }

    ~Key()
    {
        clear_secret();
    }

    bool validate(bool secret) const noexcept;

    /*
     * Performs ElGamal encryption
     * Result of an encryption is composed of two parts - g2k and encm
     *
     * @param rng initialized rnp::RNG
     * @param out encryption result
     * @param in plaintext to be encrypted
     * @param in_len length of the plaintext
     * @param key public key to be used for encryption
     *
     * @pre out: must be valid pointer to corresponding structure
     * @pre in_len: can't be bigger than byte size of `p'
     *
     * @return RNP_SUCCESS
     *         RNP_ERROR_OUT_OF_MEMORY  allocation failure
     *         RNP_ERROR_BAD_PARAMETERS wrong input provided
     */
    rnp_result_t encrypt_pkcs1(rnp::RNG &               rng,
                               Encrypted &              out,
                               const rnp::secure_bytes &in) const;

    /*
     * Performs ElGamal decryption
     *
     * @param rng initialized rnp::RNG
     * @param out decrypted plaintext. Must be capable of storing at least as much bytes as p
     * size
     * @param out_len number of plaintext bytes written will be put here
     * @param in encrypted data
     * @param key private key
     *
     * @pre out, in: must be valid pointers
     * @pre out: length must be long enough to store decrypted data. Max size of
     *           decrypted data is equal to bytes size of `p'
     *
     * @return RNP_SUCCESS
     *         RNP_ERROR_OUT_OF_MEMORY  allocation failure
     *         RNP_ERROR_BAD_PARAMETERS wrong input provided
     */
    rnp_result_t decrypt_pkcs1(rnp::RNG &         rng,
                               rnp::secure_bytes &out,
                               const Encrypted &  in) const;

    /*
     * Generates ElGamal key
     *
     * @param rng pointer to PRNG
     * @param key generated key
     * @param keybits key bitlen
     *
     * @pre `keybits' > 1024
     *
     * @returns RNP_ERROR_BAD_PARAMETERS wrong parameters provided
     *          RNP_ERROR_GENERIC internal error
     *          RNP_SUCCESS key generated and copied to `seckey'
     */
    rnp_result_t generate(rnp::RNG &rng, size_t keybits);
};

} // namespace eg
} // namespace pgp
#endif