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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: des.c,v 1.2 2000/06/17 10:52:32 mdw Exp $ |
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4 | * |
5 | * The Data Encryption Standard |
6 | * |
7 | * (c) 1999 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: des.c,v $ |
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33 | * Revision 1.2 2000/06/17 10:52:32 mdw |
34 | * Support new key size interface. |
35 | * |
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36 | * Revision 1.1 1999/09/03 08:41:11 mdw |
37 | * Initial import. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <assert.h> |
44 | #include <stdio.h> |
45 | #include <stdlib.h> |
46 | #include <string.h> |
47 | |
48 | #include <mLib/bits.h> |
49 | |
50 | #include "blkc.h" |
51 | #include "des-base.h" |
52 | #include "des.h" |
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53 | #include "gcipher.h" |
54 | |
55 | /*----- Global variables --------------------------------------------------*/ |
56 | |
57 | const octet des_keysz[] = { KSZ_SET, 7, 8, 0 }; |
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58 | |
59 | /*----- Main code ---------------------------------------------------------*/ |
60 | |
61 | /* --- @permute@ --- * |
62 | * |
63 | * Arguments: @const char *p@ = pointer to permutation table |
64 | * @uint32 a, b@ = source value to permute |
65 | * @uint32 *d@ = destination for value |
66 | * |
67 | * Returns: --- |
68 | * |
69 | * Use: Performs a 64-bit permutation. The table is given in the |
70 | * normal (but bizarre) DES bit numbering system. That's not to |
71 | * say that the tables in this source file are like the normal |
72 | * DES tables, because they're not. |
73 | */ |
74 | |
75 | static void permute(const char *p, uint32 a, uint32 b, uint32 *d) |
76 | { |
77 | uint32 x = 0, y = 0; |
78 | int i; |
79 | |
80 | for (i = 0; i < 32; i++) { |
81 | int q = p[i]; |
82 | uint32 t; |
83 | if (!q) |
84 | continue; |
85 | else if (q <= 32) |
86 | t = a; |
87 | else { |
88 | t = b; |
89 | q -= 32; |
90 | } |
91 | if (t & (1 << (32 - q))) |
92 | x |= (1 << (31 - i)); |
93 | } |
94 | |
95 | p += 32; |
96 | |
97 | for (i = 0; i < 32; i++) { |
98 | int q = p[i]; |
99 | uint32 t; |
100 | if (!q) |
101 | continue; |
102 | else if (q <= 32) |
103 | t = a; |
104 | else { |
105 | t = b; |
106 | q -= 32; |
107 | } |
108 | if (t & (1 << (32 - q))) |
109 | y |= (1 << (31 - i)); |
110 | } |
111 | |
112 | d[0] = x; |
113 | d[1] = y; |
114 | } |
115 | |
116 | /* --- @des_init@ --- * |
117 | * |
118 | * Arguments: @des_ctx *k@ = pointer to key block |
119 | * @const void *buf@ = pointer to key buffer |
120 | * @size_t sz@ = size of key material |
121 | * |
122 | * Returns: --- |
123 | * |
124 | * Use: Initializes a DES key buffer. The key buffer may be either 7 |
125 | * or 8 bytes long. If it's 8 bytes, the key is assumed to be |
126 | * padded with parity bits in the low order bit of each octet. |
127 | * These are stripped out without checking prior to the actual |
128 | * key scheduling. |
129 | */ |
130 | |
131 | void des_init(des_ctx *k, const void *buf, size_t sz) |
132 | { |
133 | uint32 x, y; |
134 | uint32 *kp = k->k; |
135 | int i; |
136 | |
137 | /* --- @pc1@ --- * |
138 | * |
139 | * This cryptographically useless permutation is used to mangle the key |
140 | * before it's subjected to the key schedule proper. I've not actually |
141 | * messed it about much except for inserting padding at the beginning of |
142 | * the two halves of the key. |
143 | */ |
144 | |
145 | static const char pc1[] = { |
146 | 0, 0, 0, 0, |
147 | 57, 49, 41, 33, 25, 17, 9, |
148 | 1, 58, 50, 42, 34, 26, 18, |
149 | 10, 2, 59, 51, 43, 35, 27, |
150 | 19, 11, 3, 60, 52, 44, 36, |
151 | 0, 0, 0, 0, |
152 | 63, 55, 47, 39, 31, 23, 15, |
153 | 7, 62, 54, 46, 38, 30, 22, |
154 | 14, 6, 61, 53, 45, 37, 29, |
155 | 21, 13, 5, 28, 20, 12, 4 |
156 | }; |
157 | |
158 | /* --- @pc2@ --- * |
159 | * |
160 | * This irritating but necessary permutation mangles the key between the |
161 | * simple rotation-based schedule and the actual XOR with which it modifies |
162 | * the behaviour of the cipher. |
163 | * |
164 | * This version of the table doesn't look much like the original. This is |
165 | * because some parts of the world have been permuted in order to make |
166 | * things simpler for the round function. In particular, everything is |
167 | * rotated left one place to avoid problems with the wraparound of the |
168 | * expansion permutation, and the key is split between odd and even S-boxes |
169 | * rather than high and low ones. That's without the complication of the |
170 | * padding bits in the representation of the 56-bit proto-key. |
171 | */ |
172 | |
173 | static const char pc2[] = { |
174 | 0, 0, 3 + 4, 28 + 4, 15 + 4, 6 + 4, 21 + 4, 10 + 4, /* S-box 2 */ |
175 | 0, 0, 16 + 4, 7 + 4, 27 + 4, 20 + 4, 13 + 4, 2 + 4, /* S-box 4 */ |
176 | 0, 0, 30 + 8, 40 + 8, 51 + 8, 45 + 8, 33 + 8, 48 + 8, /* S-box 6 */ |
177 | 0, 0, 46 + 8, 42 + 8, 50 + 8, 36 + 8, 29 + 8, 32 + 8, /* S-box 8 */ |
178 | 0, 0, 14 + 4, 17 + 4, 11 + 4, 24 + 4, 1 + 4, 5 + 4, /* S-box 1 */ |
179 | 0, 0, 23 + 4, 19 + 4, 12 + 4, 4 + 4, 26 + 4, 8 + 4, /* S-box 3 */ |
180 | 0, 0, 41 + 8, 52 + 8, 31 + 8, 37 + 8, 47 + 8, 55 + 8, /* S-box 5 */ |
181 | 0, 0, 44 + 8, 49 + 8, 39 + 8, 56 + 8, 34 + 8, 53 + 8 /* S-box 7 */ |
182 | }; |
183 | |
184 | /* --- @v@ --- * |
185 | * |
186 | * Contains the rotation amounts for the key halves. |
187 | */ |
188 | |
189 | static const char v[] = { |
190 | 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 |
191 | }; |
192 | |
193 | /* --- Extract the key into my registers --- * |
194 | * |
195 | * The 7 byte case is rather horrible. It expands the key to the 8 byte |
196 | * case before going any further. It could probably do with its own @pc1@ |
197 | * table. |
198 | */ |
199 | |
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200 | KSZ_ASSERT(des, sz); |
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201 | |
202 | if (sz == 8) { |
203 | const octet *p = buf; |
204 | x = LOAD32(p); y = LOAD32(p + 4); |
205 | } else { |
206 | const octet *p = buf; |
207 | x = LOAD32(p); |
208 | x = (x & 0xfe000000) | ((x & 0x01fffff0) >> 1); |
209 | x = (x & 0xfffe0000) | ((x & 0x0001fff8) >> 1); |
210 | x = (x & 0xfffffe00) | ((x & 0x000001fc) >> 1); |
211 | y = LOAD32(p + 3) << 1; /* Note: misaligned */ |
212 | y = (y & 0x000000fe) | ((y & 0x1fffff00) << 1); |
213 | y = (y & 0x0000fefe) | ((y & 0x3fff0000) << 1); |
214 | y = (y & 0x00fefefe) | ((y & 0x7f000000) << 1); |
215 | } |
216 | |
217 | /* --- Permute using the pointless PC1 --- */ |
218 | |
219 | { |
220 | uint32 ka[2]; |
221 | permute(pc1, x, y, ka); |
222 | x = ka[0]; y = ka[1]; |
223 | } |
224 | |
225 | /* --- Now for the key schedule proper --- */ |
226 | |
227 | for (i = 0; i < 16; i++) { |
228 | if (v[i] == 1) { |
229 | x = ((x << 1) | (x >> 27)) & 0x0fffffff; |
230 | y = ((y << 1) | (y >> 27)) & 0x0fffffff; |
231 | } else { |
232 | x = ((x << 2) | (x >> 26)) & 0x0fffffff; |
233 | y = ((y << 2) | (y >> 26)) & 0x0fffffff; |
234 | } |
235 | permute(pc2, x, y, kp); |
236 | kp += 2; |
237 | } |
238 | } |
239 | |
240 | /* --- @des_eblk@, @des_dblk@ --- * |
241 | * |
242 | * Arguments: @const des_ctx *k@ = pointer to key block |
243 | * @const uint32 s[2]@ = pointer to source block |
244 | * @uint32 d[2]@ = pointer to destination block |
245 | * |
246 | * Returns: --- |
247 | * |
248 | * Use: Low-level block encryption and decryption. |
249 | */ |
250 | |
251 | void des_eblk(const des_ctx *k, const uint32 *s, uint32 *d) |
252 | { |
253 | uint32 x = s[0], y = s[1]; |
254 | DES_IP(x, y); |
255 | DES_EBLK(k->k, x, y, x, y); |
256 | DES_IPINV(x, y); |
257 | d[0] = x, d[1] = y; |
258 | } |
259 | |
260 | void des_dblk(const des_ctx *k, const uint32 *s, uint32 *d) |
261 | { |
262 | uint32 x = s[0], y = s[1]; |
263 | DES_IP(x, y); |
264 | DES_DBLK(k->k, x, y, x, y); |
265 | DES_IPINV(x, y); |
266 | d[0] = x, d[1] = y; |
267 | } |
268 | |
269 | BLKC_TEST(DES, des) |
270 | |
271 | /*----- That's all, folks -------------------------------------------------*/ |