/*
   * Copyright (c) 2013, Kenneth MacKay
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *  * Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   *  * 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
   * HOLDER 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 _CRYPTO_ECC_H
  #define _CRYPTO_ECC_H

  #define ECC_CURVE_NIST_P192_DIGITS  3
  #define ECC_CURVE_NIST_P256_DIGITS  4
  #define ECC_MAX_DIGITS              ECC_CURVE_NIST_P256_DIGITS

  
  #define ECC_DIGITS_TO_BYTES_SHIFT 3
  
  /**
   * ecc_is_key_valid() - Validate a given ECDH private key
   *
   * @curve_id:		id representing the curve to use

   * @ndigits:		curve's number of digits

   * @private_key:	private key to be used for the given curve

   * @private_key_len:	private key length

   *
   * Returns 0 if the key is acceptable, a negative value otherwise
   */
  int ecc_is_key_valid(unsigned int curve_id, unsigned int ndigits,

  		     const u64 *private_key, unsigned int private_key_len);

  
  /**

   * ecc_gen_privkey() -  Generates an ECC private key.
   * The private key is a random integer in the range 0 < random < n, where n is a
   * prime that is the order of the cyclic subgroup generated by the distinguished
   * point G.
   * @curve_id:		id representing the curve to use
   * @ndigits:		curve number of digits
   * @private_key:	buffer for storing the generated private key
   *
   * Returns 0 if the private key was generated successfully, a negative value
   * if an error occurred.
   */
  int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey);
  
  /**

   * ecc_make_pub_key() - Compute an ECC public key

   *
   * @curve_id:		id representing the curve to use

   * @ndigits:		curve's number of digits

   * @private_key:	pregenerated private key for the given curve

   * @public_key:		buffer for storing the generated public key

   *
   * Returns 0 if the public key was generated successfully, a negative value
   * if an error occurred.
   */

  int ecc_make_pub_key(const unsigned int curve_id, unsigned int ndigits,
  		     const u64 *private_key, u64 *public_key);

  
  /**

   * crypto_ecdh_shared_secret() - Compute a shared secret

   *
   * @curve_id:		id representing the curve to use

   * @ndigits:		curve's number of digits

   * @private_key:	private key of part A

   * @public_key:		public key of counterpart B

   * @secret:		buffer for storing the calculated shared secret

   *

   * Note: It is recommended that you hash the result of crypto_ecdh_shared_secret

   * before using it for symmetric encryption or HMAC.
   *
   * Returns 0 if the shared secret was generated successfully, a negative value
   * if an error occurred.
   */

  int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,

  			      const u64 *private_key, const u64 *public_key,
  			      u64 *secret);

  #endif