~mdw / catacomb / blame
| Commit | Line | Data |
|---|---|---|
| 643eb1bb MW |
1 | /* -*-c-*- |
| 2 | * | |
| 3 | * The X448 key-agreement algorithm | |
| 4 | * | |
| 5 | * (c) 2017 Straylight/Edgeware | |
| 6 | */ | |
| 7 | ||
| 8 | /*----- Licensing notice --------------------------------------------------* | |
| 9 | * | |
| 10 | * This file is part of Catacomb. | |
| 11 | * | |
| 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. | |
| 16 | * | |
| 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. | |
| 21 | * | |
| 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, | |
| 25 | * MA 02111-1307, USA. | |
| 26 | */ | |
| 27 | ||
| 28 | #ifndef CATACOMB_X448_H | |
| 29 | #define CATACOMB_X448_H | |
| 30 | ||
| 31 | #ifdef __cplusplus | |
| 32 | extern "C" { | |
| 33 | #endif | |
| 34 | ||
| 35 | /*----- Notes on the X448 key-agreement algorithm -------------------------* | |
| 36 | * | |
| 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, | |
| c578d5d8 MW |
39 | * https://eprint.iacr.org/2015/625/. (The curve here is 4-isogenous to |
| 40 | * Hamburg's curve.) | |
| 643eb1bb MW |
41 | * |
| 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. | |
| 46 | */ | |
| 47 | ||
| 48 | /*----- Header files ------------------------------------------------------*/ | |
| 49 | ||
| 50 | #include <mLib/bits.h> | |
| 51 | ||
| 52 | #ifndef CATACOMB_KEY_H | |
| 53 | # include "key.h" | |
| 54 | #endif | |
| 55 | ||
| 56 | /*----- Key fetching ------------------------------------------------------*/ | |
| 57 | ||
| 58 | typedef struct x448_priv { key_bin priv, pub; } x448_priv; | |
| 59 | typedef struct x448_pub { key_bin pub; } x448_pub; | |
| 60 | ||
| 61 | extern const key_fetchdef x448_pubfetch[], x448_privfetch[]; | |
| 62 | #define X448_PUBFETCHSZ 3 | |
| 63 | #define X448_PRIVFETCHSZ 6 | |
| 64 | ||
| 65 | /*----- Important constants -----------------------------------------------*/ | |
| 66 | ||
| 67 | #define X448_KEYSZ 56 | |
| 68 | #define X448_PUBSZ 56 | |
| 69 | #define X448_OUTSZ 56 | |
| 70 | ||
| 71 | extern const octet x448_base[56]; | |
| 72 | ||
| 73 | /*----- Functions provided ------------------------------------------------*/ | |
| 74 | ||
| 75 | /* --- @x448@ --- * | |
| 76 | * | |
| 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 | |
| 80 | * | |
| 81 | * Returns: --- | |
| 82 | * | |
| 83 | * Use: Calculates X448 of @k@ and @qx@. | |
| 84 | */ | |
| 85 | ||
| 86 | extern void x448(octet /*zz*/[X448_OUTSZ], | |
| 87 | const octet /*k*/[X448_KEYSZ], | |
| 88 | const octet /*qx*/[X448_PUBSZ]); | |
| 89 | ||
| 90 | /*----- That's all, folks -------------------------------------------------*/ | |
| 91 | ||
| 92 | #ifdef __cplusplus | |
| 93 | } | |
| 94 | #endif | |
| 95 | ||
| 96 | #endif |