libressl/include64/openssl/curve25519.h

   1 /*      $OpenBSD: curve25519.h,v 1.3 2019/05/11 15:55:52 tb Exp $ */
   2 /*
   3  * Copyright (c) 2015, Google Inc.
   4  *
   5  * Permission to use, copy, modify, and/or distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  12  * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
  14  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  15  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 #ifndef HEADER_CURVE25519_H
  19 #define HEADER_CURVE25519_H
  20
  21 #include <stdint.h>
  22
  23 #include <openssl/opensslconf.h>
  24
  25 #if defined(__cplusplus)
  26 extern "C" {
  27 #endif
  28
  29 /*
  30  * Curve25519.
  31  *
  32  * Curve25519 is an elliptic curve. See https://tools.ietf.org/html/rfc7748.
  33  */
  34
  35 /*
  36  * X25519.
  37  *
  38  * X25519 is the Diffie-Hellman primitive built from curve25519. It is
  39  * sometimes referred to as curve25519, but X25519 is a more precise name.
  40  * See http://cr.yp.to/ecdh.html and https://tools.ietf.org/html/rfc7748.
  41  */
  42
  43 #define X25519_KEY_LENGTH 32
  44
  45 /*
  46  * X25519_keypair sets |out_public_value| and |out_private_key| to a freshly
  47  * generated, public/private key pair.
  48  */
  49 void X25519_keypair(uint8_t out_public_value[X25519_KEY_LENGTH],
  50     uint8_t out_private_key[X25519_KEY_LENGTH]);
  51
  52 /*
  53  * X25519 writes a shared key to |out_shared_key| that is calculated from the
  54  * given private key and the peer's public value. It returns one on success and
  55  * zero on error.
  56  *
  57  * Don't use the shared key directly, rather use a KDF and also include the two
  58  * public values as inputs.
  59  */
  60 int X25519(uint8_t out_shared_key[X25519_KEY_LENGTH],
  61     const uint8_t private_key[X25519_KEY_LENGTH],
  62     const uint8_t peers_public_value[X25519_KEY_LENGTH]);
  63
  64 #if defined(__cplusplus)
  65 }  /* extern C */
  66 #endif
  67
  68 #endif  /* HEADER_CURVE25519_H */