/* Copyright (c) 2016, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#ifndef OPENSSL_HEADER_NEWHOPE_H
#define OPENSSL_HEADER_NEWHOPE_H

#include <openssl/base.h>
#include <openssl/sha.h>

#if defined(__cplusplus)
extern "C" {
#endif


/* Post-quantum key agreement, based upon the reference
 * implementation. Note: this implementation does not interoperate
 * with the reference implementation!
 *
 * Source: https://github.com/tpoeppelmann/newhope
 *
 * The authors' permission to use their code is gratefully acknowledged. */


/* NEWHOPE_POLY_new returns a new |NEWHOPE_POLY| object, or NULL on error. */
OPENSSL_EXPORT NEWHOPE_POLY *NEWHOPE_POLY_new(void);

/* NEWHOPE_POLY_free frees |p|. */
OPENSSL_EXPORT void NEWHOPE_POLY_free(NEWHOPE_POLY *p);

/* NEWHOPE_OFFERMSG_LENGTH is the length of the offering party's message to the
 * accepting party. */
#define NEWHOPE_OFFERMSG_LENGTH (((1024 * 14) / 8) + 32)

/* NEWHOPE_ACCEPTMSG_LENGTH is the length of the accepting party's message to
 * the offering party. */
#define NEWHOPE_ACCEPTMSG_LENGTH (((1024 * 14) / 8) + 1024 / 4)

/* NEWHOPE_offer initializes |out_msg| and |out_sk| for a new key
 * exchange. |msg| must have room for |NEWHOPE_OFFERMSG_LENGTH| bytes. Neither
 * output may be cached. */
OPENSSL_EXPORT void NEWHOPE_offer(uint8_t out_msg[NEWHOPE_OFFERMSG_LENGTH],
                                  NEWHOPE_POLY *out_sk);

/* NEWHOPE_accept completes a key exchange given an offer message |msg|. The
 * result of the key exchange is written to |out_key|, which must have space for
 * |SHA256_DIGEST_LENGTH| bytes. The message to be send to the offering party is
 * written to |out_msg|, which must have room for |NEWHOPE_ACCEPTMSG_LENGTH|
 * bytes. Returns 1 on success and 0 on error. */
OPENSSL_EXPORT int NEWHOPE_accept(uint8_t out_key[SHA256_DIGEST_LENGTH],
                                  uint8_t out_msg[NEWHOPE_ACCEPTMSG_LENGTH],
                                  const uint8_t msg[NEWHOPE_OFFERMSG_LENGTH],
                                  size_t msg_len);

/* NEWHOPE_finish completes a key exchange for the offering party, given an
 * accept message |msg| and the previously generated secret |sk|. The result of
 * the key exchange is written to |out_key|, which must have space for
 * |SHA256_DIGEST_LENGTH| bytes. Returns 1 on success and 0 on error. */
OPENSSL_EXPORT int NEWHOPE_finish(uint8_t out_key[SHA256_DIGEST_LENGTH],
                                  const NEWHOPE_POLY *sk,
                                  const uint8_t msg[NEWHOPE_ACCEPTMSG_LENGTH],
                                  size_t msg_len);


#if defined(__cplusplus)
} /* extern "C" */
#endif

#endif /* OPENSSL_HEADER_NEWHOPE_H */