/*
   * 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

  /* One digit is u64 qword. */

  #define ECC_CURVE_NIST_P192_DIGITS  3
  #define ECC_CURVE_NIST_P256_DIGITS  4

  #define ECC_MAX_DIGITS             (512 / 64)

  
  #define ECC_DIGITS_TO_BYTES_SHIFT 3
  
  /**

   * struct ecc_point - elliptic curve point in affine coordinates
   *
   * @x:		X coordinate in vli form.
   * @y:		Y coordinate in vli form.
   * @ndigits:	Length of vlis in u64 qwords.
   */
  struct ecc_point {
  	u64 *x;
  	u64 *y;
  	u8 ndigits;
  };

  #define ECC_POINT_INIT(x, y, ndigits)	(struct ecc_point) { x, y, ndigits }

  /**
   * struct ecc_curve - definition of elliptic curve
   *
   * @name:	Short name of the curve.
   * @g:		Generator point of the curve.
   * @p:		Prime number, if Barrett's reduction is used for this curve
   *		pre-calculated value 'mu' is appended to the @p after ndigits.
   *		Use of Barrett's reduction is heuristically determined in
   *		vli_mmod_fast().
   * @n:		Order of the curve group.
   * @a:		Curve parameter a.
   * @b:		Curve parameter b.
   */
  struct ecc_curve {
  	char *name;
  	struct ecc_point g;
  	u64 *p;
  	u64 *n;
  	u64 *a;
  	u64 *b;
  };
  
  /**

   * 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);

  
  /**
   * ecc_is_pubkey_valid_partial() - Partial public key validation
   *
   * @curve:		elliptic curve domain parameters
   * @pk:			public key as a point
   *
   * Valdiate public key according to SP800-56A section 5.6.2.3.4 ECC Partial
   * Public-Key Validation Routine.
   *
   * Note: There is no check that the public key is in the correct elliptic curve
   * subgroup.
   *
   * Return: 0 if validation is successful, -EINVAL if validation is failed.
   */
  int ecc_is_pubkey_valid_partial(const struct ecc_curve *curve,
  				struct ecc_point *pk);
  
  /**

   * ecc_is_pubkey_valid_full() - Full public key validation
   *
   * @curve:		elliptic curve domain parameters
   * @pk:			public key as a point
   *
   * Valdiate public key according to SP800-56A section 5.6.2.3.3 ECC Full
   * Public-Key Validation Routine.
   *
   * Return: 0 if validation is successful, -EINVAL if validation is failed.
   */
  int ecc_is_pubkey_valid_full(const struct ecc_curve *curve,
  			     struct ecc_point *pk);
  
  /**

   * vli_is_zero() - Determine is vli is zero
   *
   * @vli:		vli to check.
   * @ndigits:		length of the @vli
   */
  bool vli_is_zero(const u64 *vli, unsigned int ndigits);
  
  /**
   * vli_cmp() - compare left and right vlis
   *
   * @left:		vli
   * @right:		vli
   * @ndigits:		length of both vlis
   *
   * Returns sign of @left - @right, i.e. -1 if @left < @right,
   * 0 if @left == @right, 1 if @left > @right.
   */
  int vli_cmp(const u64 *left, const u64 *right, unsigned int ndigits);
  
  /**
   * vli_sub() - Subtracts right from left
   *
   * @result:		where to write result
   * @left:		vli
   * @right		vli
   * @ndigits:		length of all vlis
   *
   * Note: can modify in-place.
   *
   * Return: carry bit.
   */
  u64 vli_sub(u64 *result, const u64 *left, const u64 *right,
  	    unsigned int ndigits);
  
  /**

   * vli_from_be64() - Load vli from big-endian u64 array
   *
   * @dest:		destination vli
   * @src:		source array of u64 BE values
   * @ndigits:		length of both vli and array
   */
  void vli_from_be64(u64 *dest, const void *src, unsigned int ndigits);
  
  /**
   * vli_from_le64() - Load vli from little-endian u64 array
   *
   * @dest:		destination vli
   * @src:		source array of u64 LE values
   * @ndigits:		length of both vli and array
   */
  void vli_from_le64(u64 *dest, const void *src, unsigned int ndigits);
  
  /**

   * vli_mod_inv() - Modular inversion
   *
   * @result:		where to write vli number
   * @input:		vli value to operate on
   * @mod:		modulus
   * @ndigits:		length of all vlis
   */
  void vli_mod_inv(u64 *result, const u64 *input, const u64 *mod,
  		 unsigned int ndigits);

  /**
   * vli_mod_mult_slow() - Modular multiplication
   *
   * @result:		where to write result value
   * @left:		vli number to multiply with @right
   * @right:		vli number to multiply with @left
   * @mod:		modulus
   * @ndigits:		length of all vlis
   *
   * Note: Assumes that mod is big enough curve order.
   */
  void vli_mod_mult_slow(u64 *result, const u64 *left, const u64 *right,
  		       const u64 *mod, unsigned int ndigits);
  
  /**
   * ecc_point_mult_shamir() - Add two points multiplied by scalars
   *
   * @result:		resulting point
   * @x:			scalar to multiply with @p
   * @p:			point to multiply with @x
   * @y:			scalar to multiply with @q
   * @q:			point to multiply with @y
   * @curve:		curve
   *
   * Returns result = x * p + x * q over the curve.
   * This works faster than two multiplications and addition.
   */
  void ecc_point_mult_shamir(const struct ecc_point *result,
  			   const u64 *x, const struct ecc_point *p,
  			   const u64 *y, const struct ecc_point *q,
  			   const struct ecc_curve *curve);

  #endif