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 */ 69