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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: skipjack.h,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
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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 | |
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30 | /*----- Notes on the Skipjack block cipher --------------------------------* |
31 | * |
32 | * Skipjack was designed by the NSA, as a type II algorithm to be used in the |
33 | * Clipper system. It was initially classified, so that it couldn't be used |
34 | * without the key escrow feature, though a team of `respectable' |
35 | * cryptographers, including Dorothy Denning, had a quick look at it and |
36 | * pronounced it `good', as if this was meant to be convincing. It is |
37 | * apparently a particular parameterization of a family which includes type I |
38 | * algorithms. Since declassification, Biham has discovered a miss-in-the- |
39 | * middle attack which breaks Skipjack with 31 rounds faster than brute |
40 | * force. |
41 | * |
42 | * This implementation is provided for interest's sake, and possibly for |
43 | * interoperability, rather than as a good cipher to use. |
44 | */ |
45 | |
46 | #ifndef CATACOMB_SKIPJACK_H |
47 | #define CATACOMB_SKIPJACK_H |
48 | |
49 | #ifdef __cplusplus |
50 | extern "C" { |
51 | #endif |
52 | |
53 | /*----- Header files ------------------------------------------------------*/ |
54 | |
55 | #include <stddef.h> |
56 | |
57 | #include <mLib/bits.h> |
58 | |
59 | /*----- Magical numbers ---------------------------------------------------*/ |
60 | |
61 | #define SKIPJACK_BLKSZ 8 |
62 | #define SKIPJACK_KEYSZ 10 |
63 | #define SKIPJACK_CLASS (N, B, 64) |
64 | |
65 | extern const octet skipjack_keysz[]; |
66 | |
67 | /*----- Data structures ---------------------------------------------------*/ |
68 | |
69 | typedef struct skipjack_ctx { |
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70 | uint32 ka, kb, kc, kd, ke; |
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71 | } skipjack_ctx; |
72 | |
73 | /*----- Functions provided ------------------------------------------------*/ |
74 | |
75 | /* --- @skipjack_init@ --- * |
76 | * |
77 | * Arguments: @skipjack_ctx *k@ = pointer to key block |
78 | * @const void *buf@ = pointer to key buffer |
79 | * @size_t sz@ = size of key material |
80 | * |
81 | * Returns: --- |
82 | * |
83 | * Use: Initializes a Skipjack key buffer. The key buffer must be |
84 | * exactly 10 bytes long. |
85 | */ |
86 | |
87 | extern void skipjack_init(skipjack_ctx */*k*/, |
88 | const void */*buf*/, size_t /*sz*/); |
89 | |
90 | /* --- @skipjack_eblk@, @skipjack_dblk@ --- * |
91 | * |
92 | * Arguments: @const skipjack_ctx *k@ = pointer to key block |
93 | * @const uint32 s[2]@ = pointer to source block |
94 | * @uint32 d[2]@ = pointer to skipjacktination block |
95 | * |
96 | * Returns: --- |
97 | * |
98 | * Use: Low-level block encryption and decryption. |
99 | */ |
100 | |
101 | extern void skipjack_eblk(const skipjack_ctx */*k*/, |
102 | const uint32 */*s*/, uint32 */*d*/); |
103 | extern void skipjack_dblk(const skipjack_ctx */*k*/, |
104 | const uint32 */*s*/, uint32 */*d*/); |
105 | |
106 | /*----- That's all, folks -------------------------------------------------*/ |
107 | |
108 | #ifdef __cplusplus |
109 | } |
110 | #endif |
111 | |
112 | #endif |