3 * The X448 key-agreement algorithm
5 * (c) 2017 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
12 * Catacomb is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
17 * Catacomb is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
22 * You should have received a copy of the GNU Library General Public
23 * License along with Catacomb; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
28 #ifndef CATACOMB_X448_H
29 #define CATACOMB_X448_H
35 /*----- Notes on the X448 key-agreement algorithm -------------------------*
37 * This is X448, as described in RFC7748, based on the elliptic curve defined
38 * in Mike Hamburg, `Ed448-Goldilocks, a new elliptic curve', EUROCRYPT 2016,
39 * https://eprint.iacr.org/2015/625/. (The curve here is 4-isogenous to
42 * The RFC-specified operation is simpler than the Diffie--Hellman function
43 * described in Hamburg's paper, since it doesn't involve the `Decaf'
44 * cofactor elimination procedure. Indeed, it looks very much like X25519
45 * with Hamburg's curve slotted in in place of Bernstein's.
48 /*----- Header files ------------------------------------------------------*/
50 #include <mLib/bits.h>
52 #ifndef CATACOMB_KEY_H
56 /*----- Key fetching ------------------------------------------------------*/
58 typedef struct x448_priv
{ key_bin priv
, pub
; } x448_priv
;
59 typedef struct x448_pub
{ key_bin pub
; } x448_pub
;
61 extern const key_fetchdef x448_pubfetch
[], x448_privfetch
[];
62 #define X448_PUBFETCHSZ 3
63 #define X448_PRIVFETCHSZ 6
65 /*----- Important constants -----------------------------------------------*/
71 extern const octet x448_base
[56];
73 /*----- Functions provided ------------------------------------------------*/
77 * Arguments: @octet zz[X448_OUTSZ]@ = where to put the result
78 * @const octet k[X448_KEYSZ]@ = pointer to private key
79 * @const octet qx[X448_PUBSZ]@ = pointer to public value
83 * Use: Calculates X448 of @k@ and @qx@.
86 extern void x448(octet
/*zz*/[X448_OUTSZ
],
87 const octet
/*k*/[X448_KEYSZ
],
88 const octet
/*qx*/[X448_PUBSZ
]);
90 /*----- That's all, folks -------------------------------------------------*/