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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: des.c,v 1.3 2004/04/08 01:36:15 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 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <assert.h> |
33 | #include <stdio.h> |
34 | #include <stdlib.h> |
35 | #include <string.h> |
36 | |
37 | #include <mLib/bits.h> |
38 | |
39 | #include "blkc.h" |
40 | #include "des-base.h" |
41 | #include "des.h" |
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42 | #include "gcipher.h" |
43 | |
44 | /*----- Global variables --------------------------------------------------*/ |
45 | |
46 | const octet des_keysz[] = { KSZ_SET, 7, 8, 0 }; |
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47 | |
48 | /*----- Main code ---------------------------------------------------------*/ |
49 | |
50 | /* --- @permute@ --- * |
51 | * |
52 | * Arguments: @const char *p@ = pointer to permutation table |
53 | * @uint32 a, b@ = source value to permute |
54 | * @uint32 *d@ = destination for value |
55 | * |
56 | * Returns: --- |
57 | * |
58 | * Use: Performs a 64-bit permutation. The table is given in the |
59 | * normal (but bizarre) DES bit numbering system. That's not to |
60 | * say that the tables in this source file are like the normal |
61 | * DES tables, because they're not. |
62 | */ |
63 | |
64 | static void permute(const char *p, uint32 a, uint32 b, uint32 *d) |
65 | { |
66 | uint32 x = 0, y = 0; |
67 | int i; |
68 | |
69 | for (i = 0; i < 32; i++) { |
70 | int q = p[i]; |
71 | uint32 t; |
72 | if (!q) |
73 | continue; |
74 | else if (q <= 32) |
75 | t = a; |
76 | else { |
77 | t = b; |
78 | q -= 32; |
79 | } |
80 | if (t & (1 << (32 - q))) |
81 | x |= (1 << (31 - i)); |
82 | } |
83 | |
84 | p += 32; |
85 | |
86 | for (i = 0; i < 32; i++) { |
87 | int q = p[i]; |
88 | uint32 t; |
89 | if (!q) |
90 | continue; |
91 | else if (q <= 32) |
92 | t = a; |
93 | else { |
94 | t = b; |
95 | q -= 32; |
96 | } |
97 | if (t & (1 << (32 - q))) |
98 | y |= (1 << (31 - i)); |
99 | } |
100 | |
101 | d[0] = x; |
102 | d[1] = y; |
103 | } |
104 | |
105 | /* --- @des_init@ --- * |
106 | * |
107 | * Arguments: @des_ctx *k@ = pointer to key block |
108 | * @const void *buf@ = pointer to key buffer |
109 | * @size_t sz@ = size of key material |
110 | * |
111 | * Returns: --- |
112 | * |
113 | * Use: Initializes a DES key buffer. The key buffer may be either 7 |
114 | * or 8 bytes long. If it's 8 bytes, the key is assumed to be |
115 | * padded with parity bits in the low order bit of each octet. |
116 | * These are stripped out without checking prior to the actual |
117 | * key scheduling. |
118 | */ |
119 | |
120 | void des_init(des_ctx *k, const void *buf, size_t sz) |
121 | { |
122 | uint32 x, y; |
123 | uint32 *kp = k->k; |
124 | int i; |
125 | |
126 | /* --- @pc1@ --- * |
127 | * |
128 | * This cryptographically useless permutation is used to mangle the key |
129 | * before it's subjected to the key schedule proper. I've not actually |
130 | * messed it about much except for inserting padding at the beginning of |
131 | * the two halves of the key. |
132 | */ |
133 | |
134 | static const char pc1[] = { |
135 | 0, 0, 0, 0, |
136 | 57, 49, 41, 33, 25, 17, 9, |
137 | 1, 58, 50, 42, 34, 26, 18, |
138 | 10, 2, 59, 51, 43, 35, 27, |
139 | 19, 11, 3, 60, 52, 44, 36, |
140 | 0, 0, 0, 0, |
141 | 63, 55, 47, 39, 31, 23, 15, |
142 | 7, 62, 54, 46, 38, 30, 22, |
143 | 14, 6, 61, 53, 45, 37, 29, |
144 | 21, 13, 5, 28, 20, 12, 4 |
145 | }; |
146 | |
147 | /* --- @pc2@ --- * |
148 | * |
149 | * This irritating but necessary permutation mangles the key between the |
150 | * simple rotation-based schedule and the actual XOR with which it modifies |
151 | * the behaviour of the cipher. |
152 | * |
153 | * This version of the table doesn't look much like the original. This is |
154 | * because some parts of the world have been permuted in order to make |
155 | * things simpler for the round function. In particular, everything is |
156 | * rotated left one place to avoid problems with the wraparound of the |
157 | * expansion permutation, and the key is split between odd and even S-boxes |
158 | * rather than high and low ones. That's without the complication of the |
159 | * padding bits in the representation of the 56-bit proto-key. |
160 | */ |
161 | |
162 | static const char pc2[] = { |
163 | 0, 0, 3 + 4, 28 + 4, 15 + 4, 6 + 4, 21 + 4, 10 + 4, /* S-box 2 */ |
164 | 0, 0, 16 + 4, 7 + 4, 27 + 4, 20 + 4, 13 + 4, 2 + 4, /* S-box 4 */ |
165 | 0, 0, 30 + 8, 40 + 8, 51 + 8, 45 + 8, 33 + 8, 48 + 8, /* S-box 6 */ |
166 | 0, 0, 46 + 8, 42 + 8, 50 + 8, 36 + 8, 29 + 8, 32 + 8, /* S-box 8 */ |
167 | 0, 0, 14 + 4, 17 + 4, 11 + 4, 24 + 4, 1 + 4, 5 + 4, /* S-box 1 */ |
168 | 0, 0, 23 + 4, 19 + 4, 12 + 4, 4 + 4, 26 + 4, 8 + 4, /* S-box 3 */ |
169 | 0, 0, 41 + 8, 52 + 8, 31 + 8, 37 + 8, 47 + 8, 55 + 8, /* S-box 5 */ |
170 | 0, 0, 44 + 8, 49 + 8, 39 + 8, 56 + 8, 34 + 8, 53 + 8 /* S-box 7 */ |
171 | }; |
172 | |
173 | /* --- @v@ --- * |
174 | * |
175 | * Contains the rotation amounts for the key halves. |
176 | */ |
177 | |
178 | static const char v[] = { |
179 | 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 |
180 | }; |
181 | |
182 | /* --- Extract the key into my registers --- * |
183 | * |
184 | * The 7 byte case is rather horrible. It expands the key to the 8 byte |
185 | * case before going any further. It could probably do with its own @pc1@ |
186 | * table. |
187 | */ |
188 | |
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189 | KSZ_ASSERT(des, sz); |
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190 | |
191 | if (sz == 8) { |
192 | const octet *p = buf; |
193 | x = LOAD32(p); y = LOAD32(p + 4); |
194 | } else { |
195 | const octet *p = buf; |
196 | x = LOAD32(p); |
197 | x = (x & 0xfe000000) | ((x & 0x01fffff0) >> 1); |
198 | x = (x & 0xfffe0000) | ((x & 0x0001fff8) >> 1); |
199 | x = (x & 0xfffffe00) | ((x & 0x000001fc) >> 1); |
200 | y = LOAD32(p + 3) << 1; /* Note: misaligned */ |
201 | y = (y & 0x000000fe) | ((y & 0x1fffff00) << 1); |
202 | y = (y & 0x0000fefe) | ((y & 0x3fff0000) << 1); |
203 | y = (y & 0x00fefefe) | ((y & 0x7f000000) << 1); |
204 | } |
205 | |
206 | /* --- Permute using the pointless PC1 --- */ |
207 | |
208 | { |
209 | uint32 ka[2]; |
210 | permute(pc1, x, y, ka); |
211 | x = ka[0]; y = ka[1]; |
212 | } |
213 | |
214 | /* --- Now for the key schedule proper --- */ |
215 | |
216 | for (i = 0; i < 16; i++) { |
217 | if (v[i] == 1) { |
218 | x = ((x << 1) | (x >> 27)) & 0x0fffffff; |
219 | y = ((y << 1) | (y >> 27)) & 0x0fffffff; |
220 | } else { |
221 | x = ((x << 2) | (x >> 26)) & 0x0fffffff; |
222 | y = ((y << 2) | (y >> 26)) & 0x0fffffff; |
223 | } |
224 | permute(pc2, x, y, kp); |
225 | kp += 2; |
226 | } |
227 | } |
228 | |
229 | /* --- @des_eblk@, @des_dblk@ --- * |
230 | * |
231 | * Arguments: @const des_ctx *k@ = pointer to key block |
232 | * @const uint32 s[2]@ = pointer to source block |
233 | * @uint32 d[2]@ = pointer to destination block |
234 | * |
235 | * Returns: --- |
236 | * |
237 | * Use: Low-level block encryption and decryption. |
238 | */ |
239 | |
240 | void des_eblk(const des_ctx *k, const uint32 *s, uint32 *d) |
241 | { |
242 | uint32 x = s[0], y = s[1]; |
243 | DES_IP(x, y); |
244 | DES_EBLK(k->k, x, y, x, y); |
245 | DES_IPINV(x, y); |
246 | d[0] = x, d[1] = y; |
247 | } |
248 | |
249 | void des_dblk(const des_ctx *k, const uint32 *s, uint32 *d) |
250 | { |
251 | uint32 x = s[0], y = s[1]; |
252 | DES_IP(x, y); |
253 | DES_DBLK(k->k, x, y, x, y); |
254 | DES_IPINV(x, y); |
255 | d[0] = x, d[1] = y; |
256 | } |
257 | |
258 | BLKC_TEST(DES, des) |
259 | |
260 | /*----- That's all, folks -------------------------------------------------*/ |