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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: square-mktab.c,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
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4 | * |
5 | * Build precomputed tables for the Square block cipher |
6 | * |
7 | * (c) 2000 Straylight/Edgeware |
8 | */ |
9 | |
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10 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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18 | * |
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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. |
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23 | * |
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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 | |
36 | #include <mLib/bits.h> |
37 | |
38 | /*----- Magic variables ---------------------------------------------------*/ |
39 | |
40 | static octet s[256], si[256]; |
41 | static uint32 t[4][256], ti[4][256]; |
42 | static uint32 u[4][256]; |
43 | static octet rc[32]; |
44 | |
45 | /*----- Main code ---------------------------------------------------------*/ |
46 | |
47 | /* --- @mul@ --- * |
48 | * |
49 | * Arguments: @unsigned x, y@ = polynomials over %$\gf{2^8}$% |
50 | * @unsigned m@ = modulus |
51 | * |
52 | * Returns: The product of two polynomials. |
53 | * |
54 | * Use: Computes a product of polynomials, quite slowly. |
55 | */ |
56 | |
57 | static unsigned mul(unsigned x, unsigned y, unsigned m) |
58 | { |
59 | unsigned a = 0; |
60 | unsigned i; |
61 | |
62 | for (i = 0; i < 8; i++) { |
63 | if (y & 1) |
64 | a ^= x; |
65 | y >>= 1; |
66 | x <<= 1; |
67 | if (x & 0x100) |
68 | x ^= m; |
69 | } |
70 | |
71 | return (a); |
72 | } |
73 | |
74 | /* --- @sbox@ --- * |
75 | * |
76 | * Build the S-box. |
77 | * |
78 | * This is built from inversion in the multiplicative group of |
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79 | * %$\gf{2^8}[x]/(p(x))$%, where %$p(x) = x^8+x^7+x^6+x^5+x^4+x^2+1$%, |
80 | * followed by an affine transformation treating inputs as vectors over |
81 | * %$\gf{2}$%. The result is a horrible function. |
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82 | * |
83 | * The inversion is done slightly sneakily, by building log and antilog |
84 | * tables. Let %$a$% be an element of the finite field. If the inverse of |
85 | * %$a$% is %$a^{-1}$%, then %$\log a a^{-1} = 0$%. Hence |
86 | * %$\log a = -\log a^{-1}$%. This saves fiddling about with Euclidean |
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87 | * algorithm. |
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88 | */ |
89 | |
90 | #define S_MOD 0x1f5 |
91 | |
92 | static void sbox(void) |
93 | { |
94 | octet log[256], alog[256]; |
95 | unsigned x; |
96 | unsigned i; |
97 | unsigned g; |
98 | |
99 | /* --- Find a suitable generator, and build log tables --- */ |
100 | |
101 | log[0] = 0; |
102 | for (g = 2; g < 256; g++) { |
103 | x = 1; |
104 | for (i = 0; i < 256; i++) { |
105 | log[x] = i; |
106 | alog[i] = x; |
107 | x = mul(x, g, S_MOD); |
108 | if (x == 1 && i != 254) |
109 | goto again; |
110 | } |
111 | goto done; |
112 | again:; |
113 | } |
114 | fprintf(stderr, "couldn't find generator\n"); |
115 | exit(EXIT_FAILURE); |
116 | done:; |
117 | |
118 | /* --- Now grind through and do the affine transform --- * |
119 | * |
120 | * The matrix multiply is an AND and a parity op. The add is an XOR. |
121 | */ |
122 | |
123 | for (i = 0; i < 256; i++) { |
124 | unsigned j; |
125 | octet m[] = { 0xd6, 0x7b, 0x3d, 0x1f, 0x0f, 0x05, 0x03, 0x01 }; |
126 | unsigned v = i ? alog[255 - log[i]] : 0; |
127 | |
128 | assert(i == 0 || mul(i, v, S_MOD) == 1); |
129 | |
130 | x = 0; |
131 | for (j = 0; j < 8; j++) { |
132 | unsigned r; |
133 | r = v & m[j]; |
134 | r = (r >> 4) ^ r; |
135 | r = (r >> 2) ^ r; |
136 | r = (r >> 1) ^ r; |
137 | x = (x << 1) | (r & 1); |
138 | } |
139 | x ^= 0xb1; |
140 | s[i] = x; |
141 | si[x] = i; |
142 | } |
143 | } |
144 | |
145 | /* --- @tbox@ --- * |
146 | * |
147 | * Construct the t tables for doing the round function efficiently. |
148 | */ |
149 | |
150 | static void tbox(void) |
151 | { |
152 | unsigned i; |
153 | |
154 | for (i = 0; i < 256; i++) { |
155 | uint32 a, b, c, d; |
156 | uint32 w; |
157 | |
158 | /* --- Build a forwards t-box entry --- */ |
159 | |
160 | a = s[i]; |
161 | b = a << 1; if (b & 0x100) b ^= S_MOD; |
162 | c = a ^ b; |
163 | w = (b << 0) | (a << 8) | (a << 16) | (c << 24); |
164 | t[0][i] = w; |
165 | t[1][i] = ROL32(w, 8); |
166 | t[2][i] = ROL32(w, 16); |
167 | t[3][i] = ROL32(w, 24); |
168 | |
169 | /* --- Build a backwards t-box entry --- */ |
170 | |
171 | a = mul(si[i], 0x0e, S_MOD); |
172 | b = mul(si[i], 0x09, S_MOD); |
173 | c = mul(si[i], 0x0d, S_MOD); |
174 | d = mul(si[i], 0x0b, S_MOD); |
175 | w = (a << 0) | (b << 8) | (c << 16) | (d << 24); |
176 | ti[0][i] = w; |
177 | ti[1][i] = ROL32(w, 8); |
178 | ti[2][i] = ROL32(w, 16); |
179 | ti[3][i] = ROL32(w, 24); |
180 | } |
181 | } |
182 | |
183 | /* --- @ubox@ --- * |
184 | * |
185 | * Construct the tables for performing the key schedule. |
186 | */ |
187 | |
188 | static void ubox(void) |
189 | { |
190 | unsigned i; |
191 | |
192 | for (i = 0; i < 256; i++) { |
193 | uint32 a, b, c; |
194 | uint32 w; |
195 | a = i; |
196 | b = a << 1; if (b & 0x100) b ^= S_MOD; |
197 | c = a ^ b; |
198 | w = (b << 0) | (a << 8) | (a << 16) | (c << 24); |
199 | u[0][i] = w; |
200 | u[1][i] = ROL32(w, 8); |
201 | u[2][i] = ROL32(w, 16); |
202 | u[3][i] = ROL32(w, 24); |
203 | } |
204 | } |
205 | |
206 | /* --- Round constants --- */ |
207 | |
208 | void rcon(void) |
209 | { |
210 | unsigned r = 1; |
211 | int i; |
212 | |
213 | for (i = 0; i < sizeof(rc); i++) { |
214 | rc[i] = r; |
215 | r <<= 1; |
216 | if (r & 0x100) |
217 | r ^= S_MOD; |
218 | } |
219 | } |
220 | |
221 | /* --- @main@ --- */ |
222 | |
223 | int main(void) |
224 | { |
225 | int i, j; |
226 | |
227 | puts("\ |
228 | /* -*-c-*-\n\ |
229 | *\n\ |
230 | * Square tables [generated]\n\ |
231 | */\n\ |
232 | \n\ |
233 | #ifndef CATACOMB_SQUARE_TAB_H\n\ |
234 | #define CATACOMB_SQUARE_TAB_H\n\ |
235 | "); |
236 | |
237 | /* --- Write out the S-box --- */ |
238 | |
239 | sbox(); |
240 | fputs("\ |
241 | /* --- The byte substitution and its inverse --- */\n\ |
242 | \n\ |
243 | #define SQUARE_S { \\\n\ |
244 | ", stdout); |
245 | for (i = 0; i < 256; i++) { |
246 | printf("0x%02x", s[i]); |
247 | if (i == 255) |
248 | fputs(" \\\n}\n\n", stdout); |
249 | else if (i % 8 == 7) |
250 | fputs(", \\\n ", stdout); |
251 | else |
252 | fputs(", ", stdout); |
253 | } |
254 | |
255 | fputs("\ |
256 | #define SQUARE_SI { \\\n\ |
257 | ", stdout); |
258 | for (i = 0; i < 256; i++) { |
259 | printf("0x%02x", si[i]); |
260 | if (i == 255) |
261 | fputs(" \\\n}\n\n", stdout); |
262 | else if (i % 8 == 7) |
263 | fputs(", \\\n ", stdout); |
264 | else |
265 | fputs(", ", stdout); |
266 | } |
267 | |
268 | /* --- Write out the big t tables --- */ |
269 | |
270 | tbox(); |
271 | fputs("\ |
272 | /* --- The big round tables --- */\n\ |
273 | \n\ |
274 | #define SQUARE_T { \\\n\ |
275 | { ", stdout); |
276 | for (j = 0; j < 4; j++) { |
277 | for (i = 0; i < 256; i++) { |
278 | printf("0x%08x", t[j][i]); |
279 | if (i == 255) { |
280 | if (j == 3) |
281 | fputs(" } \\\n}\n\n", stdout); |
282 | else |
283 | fputs(" }, \\\n\ |
284 | \\\n\ |
285 | { ", stdout); |
286 | } else if (i % 4 == 3) |
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287 | fputs(", \\\n ", stdout); |
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288 | else |
289 | fputs(", ", stdout); |
290 | } |
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291 | } |
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292 | |
293 | fputs("\ |
294 | #define SQUARE_TI { \\\n\ |
295 | { ", stdout); |
296 | for (j = 0; j < 4; j++) { |
297 | for (i = 0; i < 256; i++) { |
298 | printf("0x%08x", ti[j][i]); |
299 | if (i == 255) { |
300 | if (j == 3) |
301 | fputs(" } \\\n}\n\n", stdout); |
302 | else |
303 | fputs(" }, \\\n\ |
304 | \\\n\ |
305 | { ", stdout); |
306 | } else if (i % 4 == 3) |
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307 | fputs(", \\\n ", stdout); |
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308 | else |
309 | fputs(", ", stdout); |
310 | } |
311 | } |
312 | |
313 | /* --- Write out the big u tables --- */ |
314 | |
315 | ubox(); |
316 | fputs("\ |
317 | /* --- The key schedule tables --- */\n\ |
318 | \n\ |
319 | #define SQUARE_U { \\\n\ |
320 | { ", stdout); |
321 | for (j = 0; j < 4; j++) { |
322 | for (i = 0; i < 256; i++) { |
323 | printf("0x%08x", u[j][i]); |
324 | if (i == 255) { |
325 | if (j == 3) |
326 | fputs(" } \\\n}\n\n", stdout); |
327 | else |
328 | fputs(" }, \\\n\ |
329 | \\\n\ |
330 | { ", stdout); |
331 | } else if (i % 4 == 3) |
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332 | fputs(", \\\n ", stdout); |
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333 | else |
334 | fputs(", ", stdout); |
335 | } |
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336 | } |
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337 | |
338 | /* --- Round constants --- */ |
339 | |
340 | rcon(); |
341 | fputs("\ |
342 | /* --- The round constants --- */\n\ |
343 | \n\ |
344 | #define SQUARE_RCON { \\\n\ |
345 | ", stdout); |
346 | for (i = 0; i < sizeof(rc); i++) { |
347 | printf("0x%02x", rc[i]); |
348 | if (i == sizeof(rc) - 1) |
349 | fputs(" \\\n}\n\n", stdout); |
350 | else if (i % 8 == 7) |
351 | fputs(", \\\n ", stdout); |
352 | else |
353 | fputs(", ", stdout); |
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354 | } |
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355 | |
356 | /* --- Done --- */ |
357 | |
358 | puts("#endif"); |
359 | |
360 | if (fclose(stdout)) { |
361 | fprintf(stderr, "error writing data\n"); |
362 | exit(EXIT_FAILURE); |
363 | } |
364 | |
365 | return (0); |
366 | } |
367 | |
368 | /*----- That's all, folks -------------------------------------------------*/ |