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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: rijndael-mktab.c,v 1.2 2000/06/18 23:12:15 mdw Exp $ |
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4 | * |
5 | * Build precomputed tables for the Rijndael 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: rijndael-mktab.c,v $ |
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33 | * Revision 1.2 2000/06/18 23:12:15 mdw |
34 | * Change typesetting of Galois Field names. |
35 | * |
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36 | * Revision 1.1 2000/06/17 11:56:07 mdw |
37 | * New cipher. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <assert.h> |
44 | #include <stdio.h> |
45 | #include <stdlib.h> |
46 | |
47 | #include <mLib/bits.h> |
48 | |
49 | /*----- Magic variables ---------------------------------------------------*/ |
50 | |
51 | static octet s[256], si[256]; |
52 | static uint32 t[4][256], ti[4][256]; |
53 | static uint32 u[4][256]; |
54 | static octet rc[32]; |
55 | |
56 | /*----- Main code ---------------------------------------------------------*/ |
57 | |
58 | /* --- @mul@ --- * |
59 | * |
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60 | * Arguments: @unsigned x, y@ = polynomials over %$\gf{2^8}$% |
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61 | * @unsigned m@ = modulus |
62 | * |
63 | * Returns: The product of two polynomials. |
64 | * |
65 | * Use: Computes a product of polynomials, quite slowly. |
66 | */ |
67 | |
68 | static unsigned mul(unsigned x, unsigned y, unsigned m) |
69 | { |
70 | unsigned a = 0; |
71 | unsigned i; |
72 | |
73 | for (i = 0; i < 8; i++) { |
74 | if (y & 1) |
75 | a ^= x; |
76 | y >>= 1; |
77 | x <<= 1; |
78 | if (x & 0x100) |
79 | x ^= m; |
80 | } |
81 | |
82 | return (a); |
83 | } |
84 | |
85 | /* --- @sbox@ --- * |
86 | * |
87 | * Build the S-box. |
88 | * |
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89 | * This is built from inversion in the multiplicative group of |
90 | * %$\gf{2^8}[x]/(p(x))$%, where %$p(x) = x^8 + x^4 + x^3 + x + 1$%, followed |
91 | * by an affine transformation treating inputs as vectors over %$\gf{2}$%. |
92 | * The result is a horrible function. |
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93 | * |
94 | * The inversion is done slightly sneakily, by building log and antilog |
95 | * tables. Let %$a$% be an element of the finite field. If the inverse of |
96 | * %$a$% is %$a^{-1}$%, then %$\log a a^{-1} = 0$%. Hence |
97 | * %$\log a = -\log a^{-1}$%. This saves fiddling about with Euclidean |
98 | * algorithm. |
99 | */ |
100 | |
101 | #define S_MOD 0x11b |
102 | |
103 | static void sbox(void) |
104 | { |
105 | octet log[256], alog[256]; |
106 | unsigned x; |
107 | unsigned i; |
108 | unsigned g; |
109 | |
110 | /* --- Find a suitable generator, and build log tables --- */ |
111 | |
112 | log[0] = 0; |
113 | for (g = 2; g < 256; g++) { |
114 | x = 1; |
115 | for (i = 0; i < 256; i++) { |
116 | log[x] = i; |
117 | alog[i] = x; |
118 | x = mul(x, g, S_MOD); |
119 | if (x == 1 && i != 254) |
120 | goto again; |
121 | } |
122 | goto done; |
123 | again:; |
124 | } |
125 | fprintf(stderr, "couldn't find generator\n"); |
126 | exit(EXIT_FAILURE); |
127 | done:; |
128 | |
129 | /* --- Now grind through and do the affine transform --- * |
130 | * |
131 | * The matrix multiply is an AND and a parity op. The add is an XOR. |
132 | */ |
133 | |
134 | for (i = 0; i < 256; i++) { |
135 | unsigned j; |
136 | unsigned m = 0xf8; |
137 | unsigned v = i ? alog[255 - log[i]] : 0; |
138 | |
139 | assert(i == 0 || mul(i, v, S_MOD) == 1); |
140 | |
141 | x = 0; |
142 | for (j = 0; j < 8; j++) { |
143 | unsigned r; |
144 | r = v & m; |
145 | r = (r >> 4) ^ r; |
146 | r = (r >> 2) ^ r; |
147 | r = (r >> 1) ^ r; |
148 | x = (x << 1) | (r & 1); |
149 | m = ROR8(m, 1); |
150 | } |
151 | x ^= 0x63; |
152 | s[i] = x; |
153 | si[x] = i; |
154 | } |
155 | } |
156 | |
157 | /* --- @tbox@ --- * |
158 | * |
159 | * Construct the t tables for doing the round function efficiently. |
160 | */ |
161 | |
162 | static void tbox(void) |
163 | { |
164 | unsigned i; |
165 | |
166 | for (i = 0; i < 256; i++) { |
167 | uint32 a, b, c, d; |
168 | uint32 w; |
169 | |
170 | /* --- Build a forwards t-box entry --- */ |
171 | |
172 | a = s[i]; |
173 | b = a << 1; if (b & 0x100) b ^= S_MOD; |
174 | c = a ^ b; |
175 | w = (b << 0) | (a << 8) | (a << 16) | (c << 24); |
176 | t[0][i] = w; |
177 | t[1][i] = ROL32(w, 8); |
178 | t[2][i] = ROL32(w, 16); |
179 | t[3][i] = ROL32(w, 24); |
180 | |
181 | /* --- Build a backwards t-box entry --- */ |
182 | |
183 | a = mul(si[i], 0x0e, S_MOD); |
184 | b = mul(si[i], 0x09, S_MOD); |
185 | c = mul(si[i], 0x0d, S_MOD); |
186 | d = mul(si[i], 0x0b, S_MOD); |
187 | w = (a << 0) | (b << 8) | (c << 16) | (d << 24); |
188 | ti[0][i] = w; |
189 | ti[1][i] = ROL32(w, 8); |
190 | ti[2][i] = ROL32(w, 16); |
191 | ti[3][i] = ROL32(w, 24); |
192 | } |
193 | } |
194 | |
195 | /* --- @ubox@ --- * |
196 | * |
197 | * Construct the tables for performing the decryption key schedule. |
198 | */ |
199 | |
200 | static void ubox(void) |
201 | { |
202 | unsigned i; |
203 | |
204 | for (i = 0; i < 256; i++) { |
205 | uint32 a, b, c, d; |
206 | uint32 w; |
207 | a = mul(i, 0x0e, S_MOD); |
208 | b = mul(i, 0x09, S_MOD); |
209 | c = mul(i, 0x0d, S_MOD); |
210 | d = mul(i, 0x0b, S_MOD); |
211 | w = (a << 0) | (b << 8) | (c << 16) | (d << 24); |
212 | u[0][i] = w; |
213 | u[1][i] = ROL32(w, 8); |
214 | u[2][i] = ROL32(w, 16); |
215 | u[3][i] = ROL32(w, 24); |
216 | } |
217 | } |
218 | |
219 | /* --- Round constants --- */ |
220 | |
221 | void rcon(void) |
222 | { |
223 | unsigned r = 1; |
224 | int i; |
225 | |
226 | for (i = 0; i < sizeof(rc); i++) { |
227 | rc[i] = r; |
228 | r <<= 1; |
229 | if (r & 0x100) |
230 | r ^= S_MOD; |
231 | } |
232 | } |
233 | |
234 | /* --- @main@ --- */ |
235 | |
236 | int main(void) |
237 | { |
238 | int i, j; |
239 | |
240 | puts("\ |
241 | /* -*-c-*-\n\ |
242 | *\n\ |
243 | * Rijndael tables [generated]\n\ |
244 | */\n\ |
245 | \n\ |
246 | #ifndef CATACOMB_RIJNDAEL_TAB_H\n\ |
247 | #define CATACOMB_RIJNDAEL_TAB_H\n\ |
248 | "); |
249 | |
250 | /* --- Write out the S-box --- */ |
251 | |
252 | sbox(); |
253 | fputs("\ |
254 | /* --- The byte substitution and its inverse --- */\n\ |
255 | \n\ |
256 | #define RIJNDAEL_S { \\\n\ |
257 | ", stdout); |
258 | for (i = 0; i < 256; i++) { |
259 | printf("0x%02x", s[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 | fputs("\ |
269 | #define RIJNDAEL_SI { \\\n\ |
270 | ", stdout); |
271 | for (i = 0; i < 256; i++) { |
272 | printf("0x%02x", si[i]); |
273 | if (i == 255) |
274 | fputs(" \\\n}\n\n", stdout); |
275 | else if (i % 8 == 7) |
276 | fputs(", \\\n ", stdout); |
277 | else |
278 | fputs(", ", stdout); |
279 | } |
280 | |
281 | /* --- Write out the big t tables --- */ |
282 | |
283 | tbox(); |
284 | fputs("\ |
285 | /* --- The big round tables --- */\n\ |
286 | \n\ |
287 | #define RIJNDAEL_T { \\\n\ |
288 | { ", stdout); |
289 | for (j = 0; j < 4; j++) { |
290 | for (i = 0; i < 256; i++) { |
291 | printf("0x%08x", t[j][i]); |
292 | if (i == 255) { |
293 | if (j == 3) |
294 | fputs(" } \\\n}\n\n", stdout); |
295 | else |
296 | fputs(" }, \\\n\ |
297 | \\\n\ |
298 | { ", stdout); |
299 | } else if (i % 4 == 3) |
300 | fputs(", \\\n ", stdout); |
301 | else |
302 | fputs(", ", stdout); |
303 | } |
304 | } |
305 | |
306 | fputs("\ |
307 | #define RIJNDAEL_TI { \\\n\ |
308 | { ", stdout); |
309 | for (j = 0; j < 4; j++) { |
310 | for (i = 0; i < 256; i++) { |
311 | printf("0x%08x", ti[j][i]); |
312 | if (i == 255) { |
313 | if (j == 3) |
314 | fputs(" } \\\n}\n\n", stdout); |
315 | else |
316 | fputs(" }, \\\n\ |
317 | \\\n\ |
318 | { ", stdout); |
319 | } else if (i % 4 == 3) |
320 | fputs(", \\\n ", stdout); |
321 | else |
322 | fputs(", ", stdout); |
323 | } |
324 | } |
325 | |
326 | /* --- Write out the big u tables --- */ |
327 | |
328 | ubox(); |
329 | fputs("\ |
330 | /* --- The decryption key schedule tables --- */\n\ |
331 | \n\ |
332 | #define RIJNDAEL_U { \\\n\ |
333 | { ", stdout); |
334 | for (j = 0; j < 4; j++) { |
335 | for (i = 0; i < 256; i++) { |
336 | printf("0x%08x", u[j][i]); |
337 | if (i == 255) { |
338 | if (j == 3) |
339 | fputs(" } \\\n}\n\n", stdout); |
340 | else |
341 | fputs(" }, \\\n\ |
342 | \\\n\ |
343 | { ", stdout); |
344 | } else if (i % 4 == 3) |
345 | fputs(", \\\n ", stdout); |
346 | else |
347 | fputs(", ", stdout); |
348 | } |
349 | } |
350 | |
351 | /* --- Round constants --- */ |
352 | |
353 | rcon(); |
354 | fputs("\ |
355 | /* --- The round constants --- */\n\ |
356 | \n\ |
357 | #define RIJNDAEL_RCON { \\\n\ |
358 | ", stdout); |
359 | for (i = 0; i < sizeof(rc); i++) { |
360 | printf("0x%02x", rc[i]); |
361 | if (i == sizeof(rc) - 1) |
362 | fputs(" \\\n}\n\n", stdout); |
363 | else if (i % 8 == 7) |
364 | fputs(", \\\n ", stdout); |
365 | else |
366 | fputs(", ", stdout); |
367 | } |
368 | |
369 | /* --- Done --- */ |
370 | |
371 | puts("#endif"); |
372 | |
373 | if (fclose(stdout)) { |
374 | fprintf(stderr, "error writing data\n"); |
375 | exit(EXIT_FAILURE); |
376 | } |
377 | |
378 | return (0); |
379 | } |
380 | |
381 | /*----- That's all, folks -------------------------------------------------*/ |