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/* $OpenBSD: curve25519.h,v 1.3 2019/05/11 15:55:52 tb Exp $ */
/*
* Copyright (c) 2015, 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 HEADER_CURVE25519_H
#define HEADER_CURVE25519_H
#include <stdint.h>
#include <openssl/opensslconf.h>
#if defined(__cplusplus)
extern "C" {
#endif
/*
* Curve25519.
*
* Curve25519 is an elliptic curve. See https://tools.ietf.org/html/rfc7748.
*/
/*
* X25519.
*
* X25519 is the Diffie-Hellman primitive built from curve25519. It is
* sometimes referred to as curve25519, but X25519 is a more precise name.
* See http://cr.yp.to/ecdh.html and https://tools.ietf.org/html/rfc7748.
*/
#define X25519_KEY_LENGTH 32
/*
* X25519_keypair sets |out_public_value| and |out_private_key| to a freshly
* generated, public/private key pair.
*/
void X25519_keypair(uint8_t out_public_value[X25519_KEY_LENGTH],
uint8_t out_private_key[X25519_KEY_LENGTH]);
/*
* X25519 writes a shared key to |out_shared_key| that is calculated from the
* given private key and the peer's public value. It returns one on success and
* zero on error.
*
* Don't use the shared key directly, rather use a KDF and also include the two
* public values as inputs.
*/
int X25519(uint8_t out_shared_key[X25519_KEY_LENGTH],
const uint8_t private_key[X25519_KEY_LENGTH],
const uint8_t peers_public_value[X25519_KEY_LENGTH]);
#if defined(__cplusplus)
} /* extern C */
#endif
#endif /* HEADER_CURVE25519_H */
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