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/* Copyright 2017 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef __CROS_EC_CURVE25519_H
#define __CROS_EC_CURVE25519_H
#include <stdint.h>
/* 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_PRIVATE_KEY_LEN 32
#define X25519_PUBLIC_VALUE_LEN 32
/**
* Generate a public/private key pair.
* @param out_public_value generated public key.
* @param out_private_value generated private key.
*/
void X25519_keypair(uint8_t out_public_value[32], uint8_t out_private_key[32]);
/**
* Diffie-Hellman function.
* @param out_shared_key
* @param private_key
* @param out_public_value
* @return one on success and zero on error.
*
* X25519() writes a shared key to @out_shared_key that is calculated from the
* given private key and the peer's public value.
*
* 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[32], const uint8_t private_key[32],
const uint8_t peers_public_value[32]);
/**
* Compute the matching public key.
* @param out_public_value computed public key.
* @param private_key private key to use.
*
* X25519_public_from_private() calculates a Diffie-Hellman public value from
* the given private key and writes it to @out_public_value.
*/
void X25519_public_from_private(uint8_t out_public_value[32],
const uint8_t private_key[32]);
/*
* Low-level x25519 function, defined by either the generic or cortex-m0
* implementation. Must not be called directly.
*/
void x25519_scalar_mult(uint8_t out[32],
const uint8_t scalar[32],
const uint8_t point[32]);
#endif /* __CROS_EC_CURVE25519_H */
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