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