/*
 * Copyright (C) 2021 Southern Storm Software, Pty Ltd.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#ifndef LWCRYPTO_ROMULUS_M_AEAD_H
#define LWCRYPTO_ROMULUS_M_AEAD_H

#include <stddef.h>

/**
 * \file romulus-m-aead.h
 * \brief Romulus-M authenticated encryption algorithm.
 *
 * Romulus is a family of authenticated encryption algorithms that
 * are built around the SKINNY-128-384+ tweakable block cipher.
 * This API implements the Romulus-N variant which has a 128-bit key,
 * a 128-bit nonce, and a 128-bit tag.
 *
 * The Romulus-M variant is resistant to nonce reuse as long as the
 * combination of the associated data and plaintext is unique.  If the
 * same associated data and plaintext are reused under the same nonce,
 * then the scheme will leak that the same plaintext has been sent for a
 * second time but will not reveal the plaintext itself.
 *
 * References: https://romulusae.github.io/romulus/
 */

#ifdef __cplusplus
extern "C" {
#endif

/**
 * \brief Size of the key for Romulus-M.
 */
#define ROMULUS_M_KEY_SIZE 16

/**
 * \brief Size of the authentication tag for Romulus-M.
 */
#define ROMULUS_M_TAG_SIZE 16

/**
 * \brief Size of the nonce for Romulus-M.
 */
#define ROMULUS_M_NONCE_SIZE 16

/**
 * \brief Encrypts and authenticates a packet with Romulus-M.
 *
 * \param c Buffer to receive the output.
 * \param clen On exit, set to the length of the output which includes
 * the ciphertext and the 16 byte authentication tag.
 * \param m Buffer that contains the plaintext message to encrypt.
 * \param mlen Length of the plaintext message in bytes.
 * \param ad Buffer that contains associated data to authenticate
 * along with the packet but which does not need to be encrypted.
 * \param adlen Length of the associated data in bytes.
 * \param npub Points to the public nonce for the packet which must
 * be 16 bytes in length.
 * \param k Points to the 16 bytes of the key to use to encrypt the packet.
 *
 * \return 0 on success, or a negative value if there was an error in
 * the parameters.
 *
 * \sa romulus_m_aead_decrypt()
 */
int romulus_m_aead_encrypt
    (unsigned char *c, size_t *clen,
     const unsigned char *m, size_t mlen,
     const unsigned char *ad, size_t adlen,
     const unsigned char *npub,
     const unsigned char *k);

/**
 * \brief Decrypts and authenticates a packet with Romulus-M.
 *
 * \param m Buffer to receive the plaintext message on output.
 * \param mlen Receives the length of the plaintext message on output.
 * \param c Buffer that contains the ciphertext and authentication
 * tag to decrypt.
 * \param clen Length of the input data in bytes, which includes the
 * ciphertext and the 16 byte authentication tag.
 * \param ad Buffer that contains associated data to authenticate
 * along with the packet but which does not need to be encrypted.
 * \param adlen Length of the associated data in bytes.
 * \param npub Points to the public nonce for the packet which must
 * be 16 bytes in length.
 * \param k Points to the 16 bytes of the key to use to decrypt the packet.
 *
 * \return 0 on success, -1 if the authentication tag was incorrect,
 * or some other negative number if there was an error in the parameters.
 *
 * \sa romulus_m_aead_encrypt()
 */
int romulus_m_aead_decrypt
    (unsigned char *m, size_t *mlen,
     const unsigned char *c, size_t clen,
     const unsigned char *ad, size_t adlen,
     const unsigned char *npub,
     const unsigned char *k);

#ifdef __cplusplus
}
#endif

#endif