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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: square-mktab.c,v 1.2 2000/08/04 18:03:19 mdw Exp $ |
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4 | * |
5 | * Build precomputed tables for the Square 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: square-mktab.c,v $ |
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33 | * Revision 1.2 2000/08/04 18:03:19 mdw |
34 | * Fix comment describing the field in which inversion is done. |
35 | * |
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36 | * Revision 1.1 2000/07/27 18:10:27 mdw |
37 | * Build precomuted tables for Square. |
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 | * |
60 | * Arguments: @unsigned x, y@ = polynomials over %$\gf{2^8}$% |
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 | * |
89 | * This is built from inversion in the multiplicative group of |
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90 | * %$\gf{2^8}[x]/(p(x))$%, where %$p(x) = x^8+x^7+x^6+x^5+x^4+x^2+1$%, |
91 | * followed by an affine transformation treating inputs as vectors over |
92 | * %$\gf{2}$%. 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 0x1f5 |
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 | octet m[] = { 0xd6, 0x7b, 0x3d, 0x1f, 0x0f, 0x05, 0x03, 0x01 }; |
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[j]; |
145 | r = (r >> 4) ^ r; |
146 | r = (r >> 2) ^ r; |
147 | r = (r >> 1) ^ r; |
148 | x = (x << 1) | (r & 1); |
149 | } |
150 | x ^= 0xb1; |
151 | s[i] = x; |
152 | si[x] = i; |
153 | } |
154 | } |
155 | |
156 | /* --- @tbox@ --- * |
157 | * |
158 | * Construct the t tables for doing the round function efficiently. |
159 | */ |
160 | |
161 | static void tbox(void) |
162 | { |
163 | unsigned i; |
164 | |
165 | for (i = 0; i < 256; i++) { |
166 | uint32 a, b, c, d; |
167 | uint32 w; |
168 | |
169 | /* --- Build a forwards t-box entry --- */ |
170 | |
171 | a = s[i]; |
172 | b = a << 1; if (b & 0x100) b ^= S_MOD; |
173 | c = a ^ b; |
174 | w = (b << 0) | (a << 8) | (a << 16) | (c << 24); |
175 | t[0][i] = w; |
176 | t[1][i] = ROL32(w, 8); |
177 | t[2][i] = ROL32(w, 16); |
178 | t[3][i] = ROL32(w, 24); |
179 | |
180 | /* --- Build a backwards t-box entry --- */ |
181 | |
182 | a = mul(si[i], 0x0e, S_MOD); |
183 | b = mul(si[i], 0x09, S_MOD); |
184 | c = mul(si[i], 0x0d, S_MOD); |
185 | d = mul(si[i], 0x0b, S_MOD); |
186 | w = (a << 0) | (b << 8) | (c << 16) | (d << 24); |
187 | ti[0][i] = w; |
188 | ti[1][i] = ROL32(w, 8); |
189 | ti[2][i] = ROL32(w, 16); |
190 | ti[3][i] = ROL32(w, 24); |
191 | } |
192 | } |
193 | |
194 | /* --- @ubox@ --- * |
195 | * |
196 | * Construct the tables for performing the key schedule. |
197 | */ |
198 | |
199 | static void ubox(void) |
200 | { |
201 | unsigned i; |
202 | |
203 | for (i = 0; i < 256; i++) { |
204 | uint32 a, b, c; |
205 | uint32 w; |
206 | a = i; |
207 | b = a << 1; if (b & 0x100) b ^= S_MOD; |
208 | c = a ^ b; |
209 | w = (b << 0) | (a << 8) | (a << 16) | (c << 24); |
210 | u[0][i] = w; |
211 | u[1][i] = ROL32(w, 8); |
212 | u[2][i] = ROL32(w, 16); |
213 | u[3][i] = ROL32(w, 24); |
214 | } |
215 | } |
216 | |
217 | /* --- Round constants --- */ |
218 | |
219 | void rcon(void) |
220 | { |
221 | unsigned r = 1; |
222 | int i; |
223 | |
224 | for (i = 0; i < sizeof(rc); i++) { |
225 | rc[i] = r; |
226 | r <<= 1; |
227 | if (r & 0x100) |
228 | r ^= S_MOD; |
229 | } |
230 | } |
231 | |
232 | /* --- @main@ --- */ |
233 | |
234 | int main(void) |
235 | { |
236 | int i, j; |
237 | |
238 | puts("\ |
239 | /* -*-c-*-\n\ |
240 | *\n\ |
241 | * Square tables [generated]\n\ |
242 | */\n\ |
243 | \n\ |
244 | #ifndef CATACOMB_SQUARE_TAB_H\n\ |
245 | #define CATACOMB_SQUARE_TAB_H\n\ |
246 | "); |
247 | |
248 | /* --- Write out the S-box --- */ |
249 | |
250 | sbox(); |
251 | fputs("\ |
252 | /* --- The byte substitution and its inverse --- */\n\ |
253 | \n\ |
254 | #define SQUARE_S { \\\n\ |
255 | ", stdout); |
256 | for (i = 0; i < 256; i++) { |
257 | printf("0x%02x", s[i]); |
258 | if (i == 255) |
259 | fputs(" \\\n}\n\n", stdout); |
260 | else if (i % 8 == 7) |
261 | fputs(", \\\n ", stdout); |
262 | else |
263 | fputs(", ", stdout); |
264 | } |
265 | |
266 | fputs("\ |
267 | #define SQUARE_SI { \\\n\ |
268 | ", stdout); |
269 | for (i = 0; i < 256; i++) { |
270 | printf("0x%02x", si[i]); |
271 | if (i == 255) |
272 | fputs(" \\\n}\n\n", stdout); |
273 | else if (i % 8 == 7) |
274 | fputs(", \\\n ", stdout); |
275 | else |
276 | fputs(", ", stdout); |
277 | } |
278 | |
279 | /* --- Write out the big t tables --- */ |
280 | |
281 | tbox(); |
282 | fputs("\ |
283 | /* --- The big round tables --- */\n\ |
284 | \n\ |
285 | #define SQUARE_T { \\\n\ |
286 | { ", stdout); |
287 | for (j = 0; j < 4; j++) { |
288 | for (i = 0; i < 256; i++) { |
289 | printf("0x%08x", t[j][i]); |
290 | if (i == 255) { |
291 | if (j == 3) |
292 | fputs(" } \\\n}\n\n", stdout); |
293 | else |
294 | fputs(" }, \\\n\ |
295 | \\\n\ |
296 | { ", stdout); |
297 | } else if (i % 4 == 3) |
298 | fputs(", \\\n ", stdout); |
299 | else |
300 | fputs(", ", stdout); |
301 | } |
302 | } |
303 | |
304 | fputs("\ |
305 | #define SQUARE_TI { \\\n\ |
306 | { ", stdout); |
307 | for (j = 0; j < 4; j++) { |
308 | for (i = 0; i < 256; i++) { |
309 | printf("0x%08x", ti[j][i]); |
310 | if (i == 255) { |
311 | if (j == 3) |
312 | fputs(" } \\\n}\n\n", stdout); |
313 | else |
314 | fputs(" }, \\\n\ |
315 | \\\n\ |
316 | { ", stdout); |
317 | } else if (i % 4 == 3) |
318 | fputs(", \\\n ", stdout); |
319 | else |
320 | fputs(", ", stdout); |
321 | } |
322 | } |
323 | |
324 | /* --- Write out the big u tables --- */ |
325 | |
326 | ubox(); |
327 | fputs("\ |
328 | /* --- The key schedule tables --- */\n\ |
329 | \n\ |
330 | #define SQUARE_U { \\\n\ |
331 | { ", stdout); |
332 | for (j = 0; j < 4; j++) { |
333 | for (i = 0; i < 256; i++) { |
334 | printf("0x%08x", u[j][i]); |
335 | if (i == 255) { |
336 | if (j == 3) |
337 | fputs(" } \\\n}\n\n", stdout); |
338 | else |
339 | fputs(" }, \\\n\ |
340 | \\\n\ |
341 | { ", stdout); |
342 | } else if (i % 4 == 3) |
343 | fputs(", \\\n ", stdout); |
344 | else |
345 | fputs(", ", stdout); |
346 | } |
347 | } |
348 | |
349 | /* --- Round constants --- */ |
350 | |
351 | rcon(); |
352 | fputs("\ |
353 | /* --- The round constants --- */\n\ |
354 | \n\ |
355 | #define SQUARE_RCON { \\\n\ |
356 | ", stdout); |
357 | for (i = 0; i < sizeof(rc); i++) { |
358 | printf("0x%02x", rc[i]); |
359 | if (i == sizeof(rc) - 1) |
360 | fputs(" \\\n}\n\n", stdout); |
361 | else if (i % 8 == 7) |
362 | fputs(", \\\n ", stdout); |
363 | else |
364 | fputs(", ", stdout); |
365 | } |
366 | |
367 | /* --- Done --- */ |
368 | |
369 | puts("#endif"); |
370 | |
371 | if (fclose(stdout)) { |
372 | fprintf(stderr, "error writing data\n"); |
373 | exit(EXIT_FAILURE); |
374 | } |
375 | |
376 | return (0); |
377 | } |
378 | |
379 | /*----- That's all, folks -------------------------------------------------*/ |