| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Build precomputed tables for the Square block cipher |
| 4 | * |
| 5 | * (c) 2000 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 12 | * Catacomb is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU Library General Public License as |
| 14 | * published by the Free Software Foundation; either version 2 of the |
| 15 | * License, or (at your option) any later version. |
| 16 | * |
| 17 | * Catacomb is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with Catacomb; if not, write to the Free |
| 24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Header files ------------------------------------------------------*/ |
| 29 | |
| 30 | #include <assert.h> |
| 31 | #include <stdio.h> |
| 32 | #include <stdlib.h> |
| 33 | |
| 34 | #include <mLib/bits.h> |
| 35 | |
| 36 | /*----- Magic variables ---------------------------------------------------*/ |
| 37 | |
| 38 | static octet s[256], si[256]; |
| 39 | static uint32 t[4][256], ti[4][256]; |
| 40 | static uint32 u[4][256]; |
| 41 | static octet rc[35]; |
| 42 | |
| 43 | /*----- Main code ---------------------------------------------------------*/ |
| 44 | |
| 45 | /* --- @mul@ --- * |
| 46 | * |
| 47 | * Arguments: @unsigned x, y@ = polynomials over %$\gf{2^8}$% |
| 48 | * @unsigned m@ = modulus |
| 49 | * |
| 50 | * Returns: The product of two polynomials. |
| 51 | * |
| 52 | * Use: Computes a product of polynomials, quite slowly. |
| 53 | */ |
| 54 | |
| 55 | static unsigned mul(unsigned x, unsigned y, unsigned m) |
| 56 | { |
| 57 | unsigned a = 0; |
| 58 | unsigned i; |
| 59 | |
| 60 | for (i = 0; i < 8; i++) { |
| 61 | if (y & 1) |
| 62 | a ^= x; |
| 63 | y >>= 1; |
| 64 | x <<= 1; |
| 65 | if (x & 0x100) |
| 66 | x ^= m; |
| 67 | } |
| 68 | |
| 69 | return (a); |
| 70 | } |
| 71 | |
| 72 | /* --- @sbox@ --- * |
| 73 | * |
| 74 | * Build the S-box. |
| 75 | * |
| 76 | * This is built from inversion in the multiplicative group of |
| 77 | * %$\gf{2^8}[x]/(p(x))$%, where %$p(x) = x^8+x^7+x^6+x^5+x^4+x^2+1$%, |
| 78 | * followed by an affine transformation treating inputs as vectors over |
| 79 | * %$\gf{2}$%. The result is a horrible function. |
| 80 | * |
| 81 | * The inversion is done slightly sneakily, by building log and antilog |
| 82 | * tables. Let %$a$% be an element of the finite field. If the inverse of |
| 83 | * %$a$% is %$a^{-1}$%, then %$\log a a^{-1} = 0$%. Hence |
| 84 | * %$\log a = -\log a^{-1}$%. This saves fiddling about with Euclidean |
| 85 | * algorithm. |
| 86 | */ |
| 87 | |
| 88 | #define S_MOD 0x1f5 |
| 89 | |
| 90 | static void sbox(void) |
| 91 | { |
| 92 | octet log[256], alog[256]; |
| 93 | unsigned x; |
| 94 | unsigned i; |
| 95 | unsigned g; |
| 96 | |
| 97 | /* --- Find a suitable generator, and build log tables --- */ |
| 98 | |
| 99 | log[0] = 0; |
| 100 | for (g = 2; g < 256; g++) { |
| 101 | x = 1; |
| 102 | for (i = 0; i < 256; i++) { |
| 103 | log[x] = i; |
| 104 | alog[i] = x; |
| 105 | x = mul(x, g, S_MOD); |
| 106 | if (x == 1 && i != 254) |
| 107 | goto again; |
| 108 | } |
| 109 | goto done; |
| 110 | again:; |
| 111 | } |
| 112 | fprintf(stderr, "couldn't find generator\n"); |
| 113 | exit(EXIT_FAILURE); |
| 114 | done:; |
| 115 | |
| 116 | /* --- Now grind through and do the affine transform --- * |
| 117 | * |
| 118 | * The matrix multiply is an AND and a parity op. The add is an XOR. |
| 119 | */ |
| 120 | |
| 121 | for (i = 0; i < 256; i++) { |
| 122 | unsigned j; |
| 123 | octet m[] = { 0xd6, 0x7b, 0x3d, 0x1f, 0x0f, 0x05, 0x03, 0x01 }; |
| 124 | unsigned v = i ? alog[255 - log[i]] : 0; |
| 125 | |
| 126 | assert(i == 0 || mul(i, v, S_MOD) == 1); |
| 127 | |
| 128 | x = 0; |
| 129 | for (j = 0; j < 8; j++) { |
| 130 | unsigned r; |
| 131 | r = v & m[j]; |
| 132 | r = (r >> 4) ^ r; |
| 133 | r = (r >> 2) ^ r; |
| 134 | r = (r >> 1) ^ r; |
| 135 | x = (x << 1) | (r & 1); |
| 136 | } |
| 137 | x ^= 0xb1; |
| 138 | s[i] = x; |
| 139 | si[x] = i; |
| 140 | } |
| 141 | } |
| 142 | |
| 143 | /* --- @tbox@ --- * |
| 144 | * |
| 145 | * Construct the t tables for doing the round function efficiently. |
| 146 | */ |
| 147 | |
| 148 | static void tbox(void) |
| 149 | { |
| 150 | unsigned i; |
| 151 | |
| 152 | for (i = 0; i < 256; i++) { |
| 153 | uint32 a, b, c, d; |
| 154 | uint32 w; |
| 155 | |
| 156 | /* --- Build a forwards t-box entry --- */ |
| 157 | |
| 158 | a = s[i]; |
| 159 | b = a << 1; if (b & 0x100) b ^= S_MOD; |
| 160 | c = a ^ b; |
| 161 | w = (b << 0) | (a << 8) | (a << 16) | (c << 24); |
| 162 | t[0][i] = w; |
| 163 | t[1][i] = ROL32(w, 8); |
| 164 | t[2][i] = ROL32(w, 16); |
| 165 | t[3][i] = ROL32(w, 24); |
| 166 | |
| 167 | /* --- Build a backwards t-box entry --- */ |
| 168 | |
| 169 | a = mul(si[i], 0x0e, S_MOD); |
| 170 | b = mul(si[i], 0x09, S_MOD); |
| 171 | c = mul(si[i], 0x0d, S_MOD); |
| 172 | d = mul(si[i], 0x0b, S_MOD); |
| 173 | w = (a << 0) | (b << 8) | (c << 16) | (d << 24); |
| 174 | ti[0][i] = w; |
| 175 | ti[1][i] = ROL32(w, 8); |
| 176 | ti[2][i] = ROL32(w, 16); |
| 177 | ti[3][i] = ROL32(w, 24); |
| 178 | } |
| 179 | } |
| 180 | |
| 181 | /* --- @ubox@ --- * |
| 182 | * |
| 183 | * Construct the tables for performing the key schedule. |
| 184 | */ |
| 185 | |
| 186 | static void ubox(void) |
| 187 | { |
| 188 | unsigned i; |
| 189 | |
| 190 | for (i = 0; i < 256; i++) { |
| 191 | uint32 a, b, c; |
| 192 | uint32 w; |
| 193 | a = i; |
| 194 | b = a << 1; if (b & 0x100) b ^= S_MOD; |
| 195 | c = a ^ b; |
| 196 | w = (b << 0) | (a << 8) | (a << 16) | (c << 24); |
| 197 | u[0][i] = w; |
| 198 | u[1][i] = ROL32(w, 8); |
| 199 | u[2][i] = ROL32(w, 16); |
| 200 | u[3][i] = ROL32(w, 24); |
| 201 | } |
| 202 | } |
| 203 | |
| 204 | /* --- Round constants --- */ |
| 205 | |
| 206 | void rcon(void) |
| 207 | { |
| 208 | unsigned r = 1; |
| 209 | int i; |
| 210 | |
| 211 | for (i = 0; i < sizeof(rc); i++) { |
| 212 | rc[i] = r; |
| 213 | r <<= 1; |
| 214 | if (r & 0x100) |
| 215 | r ^= S_MOD; |
| 216 | } |
| 217 | } |
| 218 | |
| 219 | /* --- @main@ --- */ |
| 220 | |
| 221 | int main(void) |
| 222 | { |
| 223 | int i, j; |
| 224 | |
| 225 | puts("\ |
| 226 | /* -*-c-*-\n\ |
| 227 | *\n\ |
| 228 | * Square tables [generated]\n\ |
| 229 | */\n\ |
| 230 | \n\ |
| 231 | #include <mLib/bits.h>\n\ |
| 232 | \n\ |
| 233 | "); |
| 234 | |
| 235 | /* --- Write out the S-box --- */ |
| 236 | |
| 237 | sbox(); |
| 238 | fputs("\ |
| 239 | /* --- The byte substitution and its inverse --- */\n\ |
| 240 | \n\ |
| 241 | const octet square_s[256] = {\n\ |
| 242 | ", stdout); |
| 243 | for (i = 0; i < 256; i++) { |
| 244 | printf("0x%02x", s[i]); |
| 245 | if (i == 255) |
| 246 | fputs("\n};\n\n", stdout); |
| 247 | else if (i % 8 == 7) |
| 248 | fputs(",\n ", stdout); |
| 249 | else |
| 250 | fputs(", ", stdout); |
| 251 | } |
| 252 | |
| 253 | fputs("\ |
| 254 | const octet square_si[256] = {\n\ |
| 255 | ", stdout); |
| 256 | for (i = 0; i < 256; i++) { |
| 257 | printf("0x%02x", si[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 | /* --- Write out the big t tables --- */ |
| 267 | |
| 268 | tbox(); |
| 269 | fputs("\ |
| 270 | /* --- The big round tables --- */\n\ |
| 271 | \n\ |
| 272 | const uint32 square_t[4][256] = {\n\ |
| 273 | { ", stdout); |
| 274 | for (j = 0; j < 4; j++) { |
| 275 | for (i = 0; i < 256; i++) { |
| 276 | printf("0x%08x", t[j][i]); |
| 277 | if (i == 255) { |
| 278 | if (j == 3) |
| 279 | fputs(" }\n};\n\n", stdout); |
| 280 | else |
| 281 | fputs(" },\n\n { ", stdout); |
| 282 | } else if (i % 4 == 3) |
| 283 | fputs(",\n ", stdout); |
| 284 | else |
| 285 | fputs(", ", stdout); |
| 286 | } |
| 287 | } |
| 288 | |
| 289 | fputs("\ |
| 290 | const uint32 square_ti[4][256] = {\n\ |
| 291 | { ", stdout); |
| 292 | for (j = 0; j < 4; j++) { |
| 293 | for (i = 0; i < 256; i++) { |
| 294 | printf("0x%08x", ti[j][i]); |
| 295 | if (i == 255) { |
| 296 | if (j == 3) |
| 297 | fputs(" }\n};\n\n", stdout); |
| 298 | else |
| 299 | fputs(" },\n\n { ", stdout); |
| 300 | } else if (i % 4 == 3) |
| 301 | fputs(",\n ", stdout); |
| 302 | else |
| 303 | fputs(", ", stdout); |
| 304 | } |
| 305 | } |
| 306 | |
| 307 | /* --- Write out the big u tables --- */ |
| 308 | |
| 309 | ubox(); |
| 310 | fputs("\ |
| 311 | /* --- The key schedule tables --- */\n\ |
| 312 | \n\ |
| 313 | const uint32 square_u[4][256] = {\n\ |
| 314 | { ", stdout); |
| 315 | for (j = 0; j < 4; j++) { |
| 316 | for (i = 0; i < 256; i++) { |
| 317 | printf("0x%08x", u[j][i]); |
| 318 | if (i == 255) { |
| 319 | if (j == 3) |
| 320 | fputs(" }\n};\n\n", stdout); |
| 321 | else |
| 322 | fputs(" },\n\n { ", stdout); |
| 323 | } else if (i % 4 == 3) |
| 324 | fputs(",\n ", stdout); |
| 325 | else |
| 326 | fputs(", ", stdout); |
| 327 | } |
| 328 | } |
| 329 | |
| 330 | /* --- Round constants --- */ |
| 331 | |
| 332 | rcon(); |
| 333 | fputs("\ |
| 334 | /* --- The round constants --- */\n\ |
| 335 | \n\ |
| 336 | const octet square_rcon[35] = {\n\ |
| 337 | ", stdout); |
| 338 | for (i = 0; i < sizeof(rc); i++) { |
| 339 | printf("0x%02x", rc[i]); |
| 340 | if (i == sizeof(rc) - 1) |
| 341 | fputs("\n};\n", stdout); |
| 342 | else if (i % 8 == 7) |
| 343 | fputs(",\n ", stdout); |
| 344 | else |
| 345 | fputs(", ", stdout); |
| 346 | } |
| 347 | |
| 348 | /* --- Done --- */ |
| 349 | |
| 350 | if (fclose(stdout)) { |
| 351 | fprintf(stderr, "error writing data\n"); |
| 352 | exit(EXIT_FAILURE); |
| 353 | } |
| 354 | |
| 355 | return (0); |
| 356 | } |
| 357 | |
| 358 | /*----- That's all, folks -------------------------------------------------*/ |