aes.c

/* aes.c
 *
 * The aes/rijndael block cipher.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2000, 2001 Rafael R. Sevilla, Niels Mller
 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The GNU MP Library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/* Originally written by Rafael R. Sevilla <dido@pacific.net.ph> */

#include "aes.h"

#include <assert.h>

/* These tables combine both the S-boxes and the mixcolumn
 * transformation, so that we can perform a round's encryption or by
 * means of four table lookups and four XOR's per column of state.
 * They were generated by the makertbls.pl script. */
static const uint32_t dtbl[] = {
  0xa56363c6, 0x847c7cf8, 0x997777ee, 0x8d7b7bf6, 
  0x0df2f2ff, 0xbd6b6bd6, 0xb16f6fde, 0x54c5c591, 
  0x50303060, 0x03010102, 0xa96767ce, 0x7d2b2b56, 
  0x19fefee7, 0x62d7d7b5, 0xe6abab4d, 0x9a7676ec, 
  0x45caca8f, 0x9d82821f, 0x40c9c989, 0x877d7dfa, 
  0x15fafaef, 0xeb5959b2, 0xc947478e, 0x0bf0f0fb, 
  0xecadad41, 0x67d4d4b3, 0xfda2a25f, 0xeaafaf45, 
  0xbf9c9c23, 0xf7a4a453, 0x967272e4, 0x5bc0c09b, 
  0xc2b7b775, 0x1cfdfde1, 0xae93933d, 0x6a26264c, 
  0x5a36366c, 0x413f3f7e, 0x02f7f7f5, 0x4fcccc83, 
  0x5c343468, 0xf4a5a551, 0x34e5e5d1, 0x08f1f1f9, 
  0x937171e2, 0x73d8d8ab, 0x53313162, 0x3f15152a, 
  0x0c040408, 0x52c7c795, 0x65232346, 0x5ec3c39d, 
  0x28181830, 0xa1969637, 0x0f05050a, 0xb59a9a2f, 
  0x0907070e, 0x36121224, 0x9b80801b, 0x3de2e2df, 
  0x26ebebcd, 0x6927274e, 0xcdb2b27f, 0x9f7575ea, 
  0x1b090912, 0x9e83831d, 0x742c2c58, 0x2e1a1a34, 
  0x2d1b1b36, 0xb26e6edc, 0xee5a5ab4, 0xfba0a05b, 
  0xf65252a4, 0x4d3b3b76, 0x61d6d6b7, 0xceb3b37d, 
  0x7b292952, 0x3ee3e3dd, 0x712f2f5e, 0x97848413, 
  0xf55353a6, 0x68d1d1b9, 0x00000000, 0x2cededc1, 
  0x60202040, 0x1ffcfce3, 0xc8b1b179, 0xed5b5bb6, 
  0xbe6a6ad4, 0x46cbcb8d, 0xd9bebe67, 0x4b393972, 
  0xde4a4a94, 0xd44c4c98, 0xe85858b0, 0x4acfcf85, 
  0x6bd0d0bb, 0x2aefefc5, 0xe5aaaa4f, 0x16fbfbed, 
  0xc5434386, 0xd74d4d9a, 0x55333366, 0x94858511, 
  0xcf45458a, 0x10f9f9e9, 0x06020204, 0x817f7ffe, 
  0xf05050a0, 0x443c3c78, 0xba9f9f25, 0xe3a8a84b, 
  0xf35151a2, 0xfea3a35d, 0xc0404080, 0x8a8f8f05, 
  0xad92923f, 0xbc9d9d21, 0x48383870, 0x04f5f5f1, 
  0xdfbcbc63, 0xc1b6b677, 0x75dadaaf, 0x63212142, 
  0x30101020, 0x1affffe5, 0x0ef3f3fd, 0x6dd2d2bf, 
  0x4ccdcd81, 0x140c0c18, 0x35131326, 0x2fececc3, 
  0xe15f5fbe, 0xa2979735, 0xcc444488, 0x3917172e, 
  0x57c4c493, 0xf2a7a755, 0x827e7efc, 0x473d3d7a, 
  0xac6464c8, 0xe75d5dba, 0x2b191932, 0x957373e6, 
  0xa06060c0, 0x98818119, 0xd14f4f9e, 0x7fdcdca3, 
  0x66222244, 0x7e2a2a54, 0xab90903b, 0x8388880b, 
  0xca46468c, 0x29eeeec7, 0xd3b8b86b, 0x3c141428, 
  0x79dedea7, 0xe25e5ebc, 0x1d0b0b16, 0x76dbdbad, 
  0x3be0e0db, 0x56323264, 0x4e3a3a74, 0x1e0a0a14, 
  0xdb494992, 0x0a06060c, 0x6c242448, 0xe45c5cb8, 
  0x5dc2c29f, 0x6ed3d3bd, 0xefacac43, 0xa66262c4, 
  0xa8919139, 0xa4959531, 0x37e4e4d3, 0x8b7979f2, 
  0x32e7e7d5, 0x43c8c88b, 0x5937376e, 0xb76d6dda, 
  0x8c8d8d01, 0x64d5d5b1, 0xd24e4e9c, 0xe0a9a949, 
  0xb46c6cd8, 0xfa5656ac, 0x07f4f4f3, 0x25eaeacf, 
  0xaf6565ca, 0x8e7a7af4, 0xe9aeae47, 0x18080810, 
  0xd5baba6f, 0x887878f0, 0x6f25254a, 0x722e2e5c, 
  0x241c1c38, 0xf1a6a657, 0xc7b4b473, 0x51c6c697, 
  0x23e8e8cb, 0x7cdddda1, 0x9c7474e8, 0x211f1f3e, 
  0xdd4b4b96, 0xdcbdbd61, 0x868b8b0d, 0x858a8a0f, 
  0x907070e0, 0x423e3e7c, 0xc4b5b571, 0xaa6666cc, 
  0xd8484890, 0x05030306, 0x01f6f6f7, 0x120e0e1c, 
  0xa36161c2, 0x5f35356a, 0xf95757ae, 0xd0b9b969, 
  0x91868617, 0x58c1c199, 0x271d1d3a, 0xb99e9e27, 
  0x38e1e1d9, 0x13f8f8eb, 0xb398982b, 0x33111122, 
  0xbb6969d2, 0x70d9d9a9, 0x898e8e07, 0xa7949433, 
  0xb69b9b2d, 0x221e1e3c, 0x92878715, 0x20e9e9c9, 
  0x49cece87, 0xff5555aa, 0x78282850, 0x7adfdfa5, 
  0x8f8c8c03, 0xf8a1a159, 0x80898909, 0x170d0d1a, 
  0xdabfbf65, 0x31e6e6d7, 0xc6424284, 0xb86868d0, 
  0xc3414182, 0xb0999929, 0x772d2d5a, 0x110f0f1e, 
  0xcbb0b07b, 0xfc5454a8, 0xd6bbbb6d, 0x3a16162c, 
};

static const uint32_t itbl[] = {
  0x50a7f451, 0x5365417e, 0xc3a4171a, 0x965e273a, 
  0xcb6bab3b, 0xf1459d1f, 0xab58faac, 0x9303e34b, 
  0x55fa3020, 0xf66d76ad, 0x9176cc88, 0x254c02f5, 
  0xfcd7e54f, 0xd7cb2ac5, 0x80443526, 0x8fa362b5, 
  0x495ab1de, 0x671bba25, 0x980eea45, 0xe1c0fe5d, 
  0x02752fc3, 0x12f04c81, 0xa397468d, 0xc6f9d36b, 
  0xe75f8f03, 0x959c9215, 0xeb7a6dbf, 0xda595295, 
  0x2d83bed4, 0xd3217458, 0x2969e049, 0x44c8c98e, 
  0x6a89c275, 0x78798ef4, 0x6b3e5899, 0xdd71b927, 
  0xb64fe1be, 0x17ad88f0, 0x66ac20c9, 0xb43ace7d, 
  0x184adf63, 0x82311ae5, 0x60335197, 0x457f5362, 
  0xe07764b1, 0x84ae6bbb, 0x1ca081fe, 0x942b08f9, 
  0x58684870, 0x19fd458f, 0x876cde94, 0xb7f87b52, 
  0x23d373ab, 0xe2024b72, 0x578f1fe3, 0x2aab5566, 
  0x0728ebb2, 0x03c2b52f, 0x9a7bc586, 0xa50837d3, 
  0xf2872830, 0xb2a5bf23, 0xba6a0302, 0x5c8216ed, 
  0x2b1ccf8a, 0x92b479a7, 0xf0f207f3, 0xa1e2694e, 
  0xcdf4da65, 0xd5be0506, 0x1f6234d1, 0x8afea6c4, 
  0x9d532e34, 0xa055f3a2, 0x32e18a05, 0x75ebf6a4, 
  0x39ec830b, 0xaaef6040, 0x069f715e, 0x51106ebd, 
  0xf98a213e, 0x3d06dd96, 0xae053edd, 0x46bde64d, 
  0xb58d5491, 0x055dc471, 0x6fd40604, 0xff155060, 
  0x24fb9819, 0x97e9bdd6, 0xcc434089, 0x779ed967, 
  0xbd42e8b0, 0x888b8907, 0x385b19e7, 0xdbeec879, 
  0x470a7ca1, 0xe90f427c, 0xc91e84f8, 0x00000000, 
  0x83868009, 0x48ed2b32, 0xac70111e, 0x4e725a6c, 
  0xfbff0efd, 0x5638850f, 0x1ed5ae3d, 0x27392d36, 
  0x64d90f0a, 0x21a65c68, 0xd1545b9b, 0x3a2e3624, 
  0xb1670a0c, 0x0fe75793, 0xd296eeb4, 0x9e919b1b, 
  0x4fc5c080, 0xa220dc61, 0x694b775a, 0x161a121c, 
  0x0aba93e2, 0xe52aa0c0, 0x43e0223c, 0x1d171b12, 
  0x0b0d090e, 0xadc78bf2, 0xb9a8b62d, 0xc8a91e14, 
  0x8519f157, 0x4c0775af, 0xbbdd99ee, 0xfd607fa3, 
  0x9f2601f7, 0xbcf5725c, 0xc53b6644, 0x347efb5b, 
  0x7629438b, 0xdcc623cb, 0x68fcedb6, 0x63f1e4b8, 
  0xcadc31d7, 0x10856342, 0x40229713, 0x2011c684, 
  0x7d244a85, 0xf83dbbd2, 0x1132f9ae, 0x6da129c7, 
  0x4b2f9e1d, 0xf330b2dc, 0xec52860d, 0xd0e3c177, 
  0x6c16b32b, 0x99b970a9, 0xfa489411, 0x2264e947, 
  0xc48cfca8, 0x1a3ff0a0, 0xd82c7d56, 0xef903322, 
  0xc74e4987, 0xc1d138d9, 0xfea2ca8c, 0x360bd498, 
  0xcf81f5a6, 0x28de7aa5, 0x268eb7da, 0xa4bfad3f, 
  0xe49d3a2c, 0x0d927850, 0x9bcc5f6a, 0x62467e54, 
  0xc2138df6, 0xe8b8d890, 0x5ef7392e, 0xf5afc382, 
  0xbe805d9f, 0x7c93d069, 0xa92dd56f, 0xb31225cf, 
  0x3b99acc8, 0xa77d1810, 0x6e639ce8, 0x7bbb3bdb, 
  0x097826cd, 0xf418596e, 0x01b79aec, 0xa89a4f83, 
  0x656e95e6, 0x7ee6ffaa, 0x08cfbc21, 0xe6e815ef, 
  0xd99be7ba, 0xce366f4a, 0xd4099fea, 0xd67cb029, 
  0xafb2a431, 0x31233f2a, 0x3094a5c6, 0xc066a235, 
  0x37bc4e74, 0xa6ca82fc, 0xb0d090e0, 0x15d8a733, 
  0x4a9804f1, 0xf7daec41, 0x0e50cd7f, 0x2ff69117, 
  0x8dd64d76, 0x4db0ef43, 0x544daacc, 0xdf0496e4, 
  0xe3b5d19e, 0x1b886a4c, 0xb81f2cc1, 0x7f516546, 
  0x04ea5e9d, 0x5d358c01, 0x737487fa, 0x2e410bfb, 
  0x5a1d67b3, 0x52d2db92, 0x335610e9, 0x1347d66d, 
  0x8c61d79a, 0x7a0ca137, 0x8e14f859, 0x893c13eb, 
  0xee27a9ce, 0x35c961b7, 0xede51ce1, 0x3cb1477a, 
  0x59dfd29c, 0x3f73f255, 0x79ce1418, 0xbf37c773, 
  0xeacdf753, 0x5baafd5f, 0x146f3ddf, 0x86db4478, 
  0x81f3afca, 0x3ec468b9, 0x2c342438, 0x5f40a3c2, 
  0x72c31d16, 0x0c25e2bc, 0x8b493c28, 0x41950dff, 
  0x7101a839, 0xdeb30c08, 0x9ce4b4d8, 0x90c15664, 
  0x6184cb7b, 0x70b632d5, 0x745c6c48, 0x4257b8d0, 
};


/* Needed only for the key schedule and for final rounds */
static const uint8_t sbox[256] = {
  99, 124, 119, 123, 242, 107, 111, 197,  48,   1, 103,  43, 254, 215, 171,
  118, 202, 130, 201, 125, 250,  89,  71, 240, 173, 212, 162, 175, 156, 164,
  114, 192, 183, 253, 147,  38,  54,  63, 247, 204,  52, 165, 229, 241, 113,
  216,  49,  21,  4, 199,  35, 195,  24, 150,   5, 154,   7,  18, 128, 226,
  235,  39, 178, 117,  9, 131,  44,  26,  27, 110,  90, 160,  82,  59, 214,
  179,  41, 227,  47, 132, 83, 209,   0, 237,  32, 252, 177,  91, 106, 203,
  190,  57,  74,  76,  88, 207, 208, 239, 170, 251,  67,  77,  51, 133,  69,
  249,   2, 127,  80,  60, 159, 168, 81, 163,  64, 143, 146, 157,  56, 245,
  188, 182, 218,  33,  16, 255, 243, 210, 205,  12,  19, 236,  95, 151,  68,
  23, 196, 167, 126,  61, 100,  93,  25, 115, 96, 129,  79, 220,  34,  42,
  144, 136,  70, 238, 184,  20, 222,  94,  11, 219, 224,  50,  58,  10,  73,
  6,  36,  92, 194, 211, 172,  98, 145, 149, 228, 121, 231, 200,  55, 109, 
  141, 213,  78, 169, 108,  86, 244, 234, 101, 122, 174,   8, 186, 120,  37,
  46,  28, 166, 180, 198, 232, 221, 116,  31,  75, 189, 139, 138, 112,  62,
  181, 102,  72,   3, 246,  14,  97,  53,  87, 185, 134, 193,  29, 158, 225,
  248, 152,  17, 105, 217, 142, 148, 155,  30, 135, 233, 206,  85,  40, 223, 
  140, 161, 137,  13, 191, 230,  66, 104,  65, 153,  45,  15, 176,  84, 187,
  22, 
};

static const uint8_t isbox[256] = {
  82,   9, 106, 213,  48,  54, 165,  56, 191,  64, 163, 158, 129, 243, 215,
  251, 124, 227,  57, 130, 155,  47, 255, 135,  52, 142,  67,  68, 196, 222,
  233, 203, 84, 123, 148,  50, 166, 194,  35,  61, 238,  76, 149,  11,  66,
  250, 195,  78,  8,  46, 161, 102,  40, 217,  36, 178, 118,  91, 162,  73,
  109, 139, 209,  37, 114, 248, 246, 100, 134, 104, 152,  22, 212, 164,  92,
  204,  93, 101, 182, 146, 108, 112,  72,  80, 253, 237, 185, 218,  94,  21,
  70,  87, 167, 141, 157, 132, 144, 216, 171,   0, 140, 188, 211,  10, 247,
  228,  88,   5, 184, 179,  69,   6, 208,  44,  30, 143, 202,  63,  15,   2,
  193, 175, 189,   3,   1,  19, 138, 107,  58, 145,  17,  65,  79, 103, 220,
  234, 151, 242, 207, 206, 240, 180, 230, 115, 150, 172, 116,  34, 231, 173,
  53, 133, 226, 249,  55, 232,  28, 117, 223, 110,  71, 241,  26, 113,  29,
  41, 197, 137, 111, 183,  98,  14, 170,  24, 190,  27, 252,  86,  62,  75,
  198, 210, 121,  32, 154, 219, 192, 254, 120, 205,  90, 244,  31, 221, 168,
  51, 136,   7, 199,  49, 177,  18,  16,  89,  39, 128, 236,  95,  96,  81,
  127, 169,  25, 181,  74,  13,  45, 229, 122, 159, 147, 201, 156, 239, 160,
  224,  59,  77, 174,  42, 245, 176, 200, 235, 187,  60, 131,  83, 153,  97,
  23,  43,   4, 126, 186, 119, 214,  38, 225, 105,  20,  99,  85,  33,  12,
  125, 
};

/* Used only by the key schedule */
static const uint8_t Logtable[256] = {
  0,   0,  25,   1,  50,   2,  26, 198,  75, 199,  27, 104,  51, 238, 223,  3,
  100,   4, 224,  14,  52, 141, 129, 239,  76, 113,   8, 200, 248, 105,  28,
  193, 125, 194,  29, 181, 249, 185,  39, 106,  77, 228, 166, 114, 154, 201,
  9, 120, 101,  47, 138,   5,  33,  15, 225,  36,  18, 240, 130,  69,  53,
  147, 218, 142, 150, 143, 219, 189,  54, 208, 206, 148,  19,  92, 210, 241,
  64,  70, 131,  56, 102, 221, 253,  48, 191,   6, 139,  98, 179,  37, 226,
  152,  34, 136, 145,  16, 126, 110,  72, 195, 163, 182,  30,  66,  58, 107,
  40,  84, 250, 133,  61, 186, 43, 121,  10,  21, 155, 159,  94, 202,  78,
  212, 172, 229, 243, 115, 167,  87, 175,  88, 168,  80, 244, 234, 214, 116,
  79, 174, 233, 213, 231, 230, 173, 232, 44, 215, 117, 122, 235,  22,  11,
  245,  89, 203,  95, 176, 156, 169,  81, 160, 127,  12, 246, 111,  23, 196,
  73, 236, 216,  67,  31,  45, 164, 118, 123, 183, 204, 187,  62,  90, 251,
  96, 177, 134,  59,  82, 161, 108, 170,  85,  41, 157, 151, 178, 135, 144,
  97, 190, 220, 252, 188, 149, 207, 205,  55,  63,  91, 209, 83,  57, 132,
  60,  65, 162, 109,  71,  20,  42, 158,  93,  86, 242, 211, 171, 68,  17,
  146, 217,  35,  32,  46, 137, 180, 124, 184,  38, 119, 153, 227, 165, 103,  
  74, 237, 222, 197,  49, 254,  24,  13,  99, 140, 128, 192, 247, 112,   7, 
};

static const uint8_t Alogtable[256] = {
  1,   3,   5,  15,  17,  51,  85, 255,  26,  46, 114, 150, 161, 248,  19, 
  53, 95, 225,  56,  72, 216, 115, 149, 164, 247,   2,   6,  10,  30,  34,
  102, 170, 229,  52,  92, 228,  55,  89, 235,  38, 106, 190, 217, 112, 144,
  171, 230,  49,  83, 245,   4,  12,  20,  60,  68, 204,  79, 209, 104, 184,
  211, 110, 178, 205,  76, 212, 103, 169, 224,  59,  77, 215,  98, 166, 241,
  8,  24,  40, 120, 136, 131, 158, 185, 208, 107, 189, 220, 127, 129, 152,
  179, 206,  73, 219, 118, 154, 181, 196,  87, 249,  16,  48,  80, 240,  11,
  29,  39, 105, 187, 214,  97, 163, 254,  25,  43, 125, 135, 146, 173, 236,
  47, 113, 147, 174, 233,  32,  96, 160, 251,  22,  58,  78, 210, 109, 183,
  194,  93, 231,  50,  86, 250,  21,  63,  65, 195,  94, 226,  61,  71, 201,
  64, 192,  91, 237,  44, 116, 156, 191, 218, 117, 159, 186, 213, 100, 172,
  239,  42, 126, 130, 157, 188, 223, 122, 142, 137, 128, 155, 182, 193,  88,
  232,  35, 101, 175, 234,  37, 111, 177, 200,  67, 197,  84, 252,  31,  33,
  99, 165, 244,   7,   9,  27,  45, 119, 153, 176, 203,  70, 202,  69, 207,
  74, 222, 121, 139, 134, 145, 168, 227,  62,  66, 198,  81, 243,  14,  18,
  54,  90, 238,  41, 123, 141, 140, 143, 138, 133, 148, 167, 242,  13,  23,
  57,  75, 221, 124, 132, 151, 162, 253,  28,  36, 108, 180, 199,  82, 246, 1, 
};

#define ROTBYTE(x) (((x) >> 8) | (((x) & 0xff) << 24))
#define ROTRBYTE(x) (((x) << 8) | (((x) >> 24) & 0xff))
#define SUBBYTE(x, box) (((box)[((x) & 0xff)]) | \
                        ((box)[(((x) >> 8) & 0xff)] << 8) | \
                        ((box)[(((x) >> 16) & 0xff)] << 16) | \
                        ((box)[(((x) >> 24) & 0xff)] << 24))

static uint8_t
xtime(uint8_t a)
{
  uint8_t b;

  b = (a & 0x80) ? 0x1b : 0;
  a<<=1;
  a^=b;
  return(a);
}

static uint8_t
mul(uint8_t a, uint8_t b)
{
  if (a && b) return Alogtable[(Logtable[a] + Logtable[b])%255];
  else return 0;
}

static void
inv_mix_column(uint32_t *a, uint32_t *b)
{
  uint8_t c[4][4];
  unsigned i, j;
	
  for(j = 0; j < 4; j++)
    {
      for(i = 0; i < 4; i++)
	{
	  c[j][i] = mul(0xe, (a[j] >> i*8) & 0xff)
	    ^ mul(0xb, (a[j] >> ((i+1)%4)*8) & 0xff)
	    ^ mul(0xd, (a[j] >> ((i+2)%4)*8) & 0xff)
	    ^ mul(0x9, (a[j] >> ((i+3)%4)*8) & 0xff);
	}
    }
  for(i = 0; i < 4; i++)
    {
      b[i] = 0;
      for(j = 0; j < 4; j++)
	b[i] |= c[i][j] << (j*8);
    }
}

/* FIXME: Perhaps we should have separate fucntion for encryption and decryption keys?
 * It seems unnecessary to compute the inverse subkeys if we're not going to use them.
 * Can one define an aes_inverse function? */

void
aes_set_key(struct aes_ctx *ctx, unsigned keysize, const uint8_t *key)
{
  unsigned nk, nr, i, lastkey;
  uint32_t temp, rcon;

  assert(keysize >= AES_MIN_KEY_SIZE);
  assert(keysize <= AES_MAX_KEY_SIZE);
  
  /* Truncate keysizes to the valid key sizes provided by Rijndael */
  if (keysize == 32) {
    nk = 8;
    nr = 14;
  } else if (keysize >= 24) {
    nk = 6;
    nr = 12;
  } else { /* must be 16 or more */
    nk = 4;
    nr = 10;
  }

  lastkey = (AES_BLOCK_SIZE/4) * (nr + 1);
  ctx->nrounds = nr;
  rcon = 1;
  for (i=0; i<nk; i++)
    {
      ctx->keys[i] = key[i*4] + (key[i*4+1]<<8) + (key[i*4+2]<<16) +
	(key[i*4+3]<<24);
    }

  for (i=nk; i<lastkey; i++)
    {
      temp = ctx->keys[i-1];
      if (i % nk == 0)
	{
	  temp = SUBBYTE(ROTBYTE(temp), sbox) ^ rcon;
	  rcon = (uint32_t)xtime((uint8_t)rcon&0xff);
	}
      else if (nk > 6 && (i%nk) == 4)
	{
	  temp = SUBBYTE(temp, sbox);
	}
      ctx->keys[i] = ctx->keys[i-nk] ^ temp;
    }
  
  /* Generate the inverse keys */
  for (i=0; i<4; i++)
    {
      ctx->ikeys[i] = ctx->keys[i];
      ctx->ikeys[lastkey-4 + i] = ctx->keys[lastkey-4 + i];
    }
  for (i=4; i<lastkey-4; i+=4)
    inv_mix_column(&(ctx->keys[i]), &(ctx->ikeys[i]));
}

/* Key addition that also packs every byte in the key to a word rep. */
static void
key_addition_8to32(const uint8_t *txt, const uint32_t *keys, uint32_t *out)
{
  const uint8_t *ptr;
  unsigned i, j;
  uint32_t val;

  ptr = txt;
  for (i=0; i<4; i++)
    {
      /* FIXME: Use the READ_UINT32 or LE_READ_UINT32 macro. */
      val = 0;
      for (j=0; j<4; j++)
	val |= (*ptr++ << 8*j);
      out[i] = keys[i]^val;
    }
}

static void
key_addition32(const uint32_t *txt, const uint32_t *keys, uint32_t *out)
{
  unsigned i;

  for (i=0; i<4; i++)
    out[i] = keys[i] ^ txt[i];
}

static void
key_addition32to8(const uint32_t *txt, const uint32_t *keys, uint8_t *out)
{
  uint8_t *ptr;
  unsigned i, j;
  uint32_t val;

  ptr = out;
  for (i=0; i<4; i++)
    {
      /* FIXME: Use WRITE_UINT32 or LE_WRITE_UINT32 */
      val = txt[i] ^ keys[i];
      for (j=0; j<4; j++)
	*ptr++ = (val >> 8*j) & 0xff;
    }
}

static const unsigned idx[4][4] = {
  { 0, 1, 2, 3 },
  { 1, 2, 3, 0 },
  { 2, 3, 0, 1 },
  { 3, 0, 1, 2 } };

void
aes_encrypt(struct aes_ctx *ctx,
	    unsigned length, uint8_t *dst,
	    const uint8_t *src)
{
  unsigned r, j;
  uint32_t wtxt[4], t[4];		/* working ciphertext */
  uint32_t e;

  assert(!(length % AES_BLOCK_SIZE));

  for (; length;
       length -= AES_BLOCK_SIZE, src += AES_BLOCK_SIZE, dst += AES_BLOCK_SIZE)
    {
      key_addition_8to32(src, ctx->keys, wtxt);
      for (r=1; r<ctx->nrounds; r++)
	{
	  for (j=0; j<4; j++)
	    {
	      t[j] = dtbl[wtxt[j] & 0xff] ^
		ROTRBYTE(dtbl[(wtxt[idx[1][j]] >> 8) & 0xff]^
			 ROTRBYTE(dtbl[(wtxt[idx[2][j]] >> 16) & 0xff] ^
				  ROTRBYTE(dtbl[(wtxt[idx[3][j]] >> 24) & 0xff])));
	    }
	  key_addition32(t, ctx->keys + r*4, wtxt);
	}
  
      /* last round is special: there is no mixcolumn, so we can't use the big
	 tables. */
      for (j=0; j<4; j++)
	{
	  e = wtxt[j] & 0xff;
	  e |= (wtxt[idx[1][j]]) & (0xff << 8);
	  e |= (wtxt[idx[2][j]]) & (0xff << 16);
	  e |= (wtxt[idx[3][j]]) & (0xff << 24);
	  t[j] = e;
	}
      for (j=0; j<4; j++)
	t[j] = SUBBYTE(t[j], sbox);

      key_addition32to8(t, ctx->keys + 4*ctx->nrounds, dst);
    }
}

static const unsigned iidx[4][4] = {
  { 0, 1, 2, 3 },
  { 3, 0, 1, 2 },
  { 2, 3, 0, 1 },
  { 1, 2, 3, 0 } };

void
aes_decrypt(struct aes_ctx *ctx,
	    unsigned length, uint8_t *dst,
	    const uint8_t *src)
{
  unsigned r, j;
  uint32_t wtxt[4], t[4];		/* working ciphertext */
  uint32_t e;

  assert(!(length % AES_BLOCK_SIZE));

  for (; length;
       length -= AES_BLOCK_SIZE, src += AES_BLOCK_SIZE, dst += AES_BLOCK_SIZE)
    {
      key_addition_8to32(src, ctx->ikeys + 4*ctx->nrounds, wtxt);
      for (r=ctx->nrounds-1; r> 0;  r--)
	{
	  for (j=0; j<4; j++)
	    {
	      t[j] = itbl[wtxt[j] & 0xff] ^
		ROTRBYTE(itbl[(wtxt[iidx[1][j]] >> 8) & 0xff]^
			 ROTRBYTE(itbl[(wtxt[iidx[2][j]] >> 16) & 0xff] ^
				  ROTRBYTE(itbl[(wtxt[iidx[3][j]] >> 24) & 0xff])));
	    }
	  key_addition32(t, ctx->ikeys + r*4, wtxt);
	}
      /* last round is special: there is no mixcolumn, so we can't use the big
	 tables. */
      for (j=0; j<4; j++)
	{
	  e = wtxt[j] & 0xff;
	  e |= (wtxt[iidx[1][j]]) & (0xff << 8);
	  e |= (wtxt[iidx[2][j]]) & (0xff << 16);
	  e |= (wtxt[iidx[3][j]]) & (0xff << 24);
	  t[j] = e;
	}
      for (j=0; j<4; j++)
	t[j] = SUBBYTE(t[j], isbox);

      key_addition32to8(t, ctx->ikeys, dst);
    }
}