| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: skipjack.h,v 1.2 2000/08/01 00:28:34 mdw Exp $ |
| 4 | * |
| 5 | * The Skipjack block cipher |
| 6 | * |
| 7 | * (c) 2000 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of Catacomb. |
| 13 | * |
| 14 | * Catacomb is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU Library General Public License as |
| 16 | * published by the Free Software Foundation; either version 2 of the |
| 17 | * License, or (at your option) any later version. |
| 18 | * |
| 19 | * Catacomb is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU Library General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU Library General Public |
| 25 | * License along with Catacomb; if not, write to the Free |
| 26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 27 | * MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Revision history --------------------------------------------------* |
| 31 | * |
| 32 | * $Log: skipjack.h,v $ |
| 33 | * Revision 1.2 2000/08/01 00:28:34 mdw |
| 34 | * Performance improvement: read keys in as 32-bit words and deal them out |
| 35 | * byte-by-byte. |
| 36 | * |
| 37 | * Revision 1.1 2000/07/15 15:39:33 mdw |
| 38 | * The NSA's Skipjack block cipher. |
| 39 | * |
| 40 | */ |
| 41 | |
| 42 | /*----- Notes on the Skipjack block cipher --------------------------------* |
| 43 | * |
| 44 | * Skipjack was designed by the NSA, as a type II algorithm to be used in the |
| 45 | * Clipper system. It was initially classified, so that it couldn't be used |
| 46 | * without the key escrow feature, though a team of `respectable' |
| 47 | * cryptographers, including Dorothy Denning, had a quick look at it and |
| 48 | * pronounced it `good', as if this was meant to be convincing. It is |
| 49 | * apparently a particular parameterization of a family which includes type I |
| 50 | * algorithms. Since declassification, Biham has discovered a miss-in-the- |
| 51 | * middle attack which breaks Skipjack with 31 rounds faster than brute |
| 52 | * force. |
| 53 | * |
| 54 | * This implementation is provided for interest's sake, and possibly for |
| 55 | * interoperability, rather than as a good cipher to use. |
| 56 | */ |
| 57 | |
| 58 | #ifndef CATACOMB_SKIPJACK_H |
| 59 | #define CATACOMB_SKIPJACK_H |
| 60 | |
| 61 | #ifdef __cplusplus |
| 62 | extern "C" { |
| 63 | #endif |
| 64 | |
| 65 | /*----- Header files ------------------------------------------------------*/ |
| 66 | |
| 67 | #include <stddef.h> |
| 68 | |
| 69 | #include <mLib/bits.h> |
| 70 | |
| 71 | /*----- Magical numbers ---------------------------------------------------*/ |
| 72 | |
| 73 | #define SKIPJACK_BLKSZ 8 |
| 74 | #define SKIPJACK_KEYSZ 10 |
| 75 | #define SKIPJACK_CLASS (N, B, 64) |
| 76 | |
| 77 | extern const octet skipjack_keysz[]; |
| 78 | |
| 79 | /*----- Data structures ---------------------------------------------------*/ |
| 80 | |
| 81 | typedef struct skipjack_ctx { |
| 82 | uint32 ka, kb, kc, kd, ke; |
| 83 | } skipjack_ctx; |
| 84 | |
| 85 | /*----- Functions provided ------------------------------------------------*/ |
| 86 | |
| 87 | /* --- @skipjack_init@ --- * |
| 88 | * |
| 89 | * Arguments: @skipjack_ctx *k@ = pointer to key block |
| 90 | * @const void *buf@ = pointer to key buffer |
| 91 | * @size_t sz@ = size of key material |
| 92 | * |
| 93 | * Returns: --- |
| 94 | * |
| 95 | * Use: Initializes a Skipjack key buffer. The key buffer must be |
| 96 | * exactly 10 bytes long. |
| 97 | */ |
| 98 | |
| 99 | extern void skipjack_init(skipjack_ctx */*k*/, |
| 100 | const void */*buf*/, size_t /*sz*/); |
| 101 | |
| 102 | /* --- @skipjack_eblk@, @skipjack_dblk@ --- * |
| 103 | * |
| 104 | * Arguments: @const skipjack_ctx *k@ = pointer to key block |
| 105 | * @const uint32 s[2]@ = pointer to source block |
| 106 | * @uint32 d[2]@ = pointer to skipjacktination block |
| 107 | * |
| 108 | * Returns: --- |
| 109 | * |
| 110 | * Use: Low-level block encryption and decryption. |
| 111 | */ |
| 112 | |
| 113 | extern void skipjack_eblk(const skipjack_ctx */*k*/, |
| 114 | const uint32 */*s*/, uint32 */*d*/); |
| 115 | extern void skipjack_dblk(const skipjack_ctx */*k*/, |
| 116 | const uint32 */*s*/, uint32 */*d*/); |
| 117 | |
| 118 | /*----- That's all, folks -------------------------------------------------*/ |
| 119 | |
| 120 | #ifdef __cplusplus |
| 121 | } |
| 122 | #endif |
| 123 | |
| 124 | #endif |