2 ---------------------------------------------------------------------------
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3 Copyright (c) 2003, Dr Brian Gladman < >, Worcester, UK.
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8 The free distribution and use of this software in both source and binary
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9 form is allowed (with or without changes) provided that:
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11 1. distributions of this source code include the above copyright
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12 notice, this list of conditions and the following disclaimer;
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14 2. distributions in binary form include the above copyright
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15 notice, this list of conditions and the following disclaimer
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16 in the documentation and/or other associated materials;
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18 3. the copyright holder's name is not used to endorse products
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19 built using this software without specific written permission.
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21 ALTERNATIVELY, provided that this notice is retained in full, this product
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22 may be distributed under the terms of the GNU General Public License (GPL),
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23 in which case the provisions of the GPL apply INSTEAD OF those given above.
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27 This software is provided 'as is' with no explicit or implied warranties
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28 in respect of its properties, including, but not limited to, correctness
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29 and/or fitness for purpose.
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30 ---------------------------------------------------------------------------
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31 Issue Date: 26/08/2003
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39 #if defined(FIXED_TABLES)
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41 /* implemented in case of wrong call for fixed tables */
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47 #else /* dynamic table generation */
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49 #if !defined(FF_TABLES)
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51 /* Generate the tables for the dynamic table option
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53 It will generally be sensible to use tables to compute finite
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54 field multiplies and inverses but where memory is scarse this
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55 code might sometimes be better. But it only has effect during
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56 initialisation so its pretty unimportant in overall terms.
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59 /* return 2 ^ (n - 1) where n is the bit number of the highest bit
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60 set in x with x in the range 1 < x < 0x00000200. This form is
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61 used so that locals within fi can be bytes rather than words
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64 static aes_08t hibit(const aes_32t x)
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65 { aes_08t r = (aes_08t)((x >> 1) | (x >> 2));
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69 return (r + 1) >> 1;
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72 /* return the inverse of the finite field element x */
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74 static aes_08t fi(const aes_08t x)
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75 { aes_08t p1 = x, p2 = BPOLY, n1 = hibit(x), n2 = 0x80, v1 = 1, v2 = 0;
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85 n2 /= n1; p2 ^= p1 * n2; v2 ^= v1 * n2; n2 = hibit(p2);
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92 n1 /= n2; p1 ^= p2 * n1; v1 ^= v2 * n1; n1 = hibit(p1);
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99 /* The forward and inverse affine transformations used in the S-box */
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101 #define fwd_affine(x) \
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102 (w = (aes_32t)x, w ^= (w<<1)^(w<<2)^(w<<3)^(w<<4), 0x63^(aes_08t)(w^(w>>8)))
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104 #define inv_affine(x) \
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105 (w = (aes_32t)x, w = (w<<1)^(w<<3)^(w<<6), 0x05^(aes_08t)(w^(w>>8)))
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107 static int init = 0;
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109 void gen_tabs(void)
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112 #if defined(FF_TABLES)
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114 aes_08t pow[512], log[256];
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117 /* log and power tables for GF(2^8) finite field with
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118 WPOLY as modular polynomial - the simplest primitive
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119 root is 0x03, used here to generate the tables
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125 pow[i] = (aes_08t)w;
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126 pow[i + 255] = (aes_08t)w;
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127 log[w] = (aes_08t)i++;
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128 w ^= (w << 1) ^ (w & 0x80 ? WPOLY : 0);
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136 for(i = 0, w = 1; i < RC_LENGTH; ++i)
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138 t_set(r,c)[i] = bytes2word(w, 0, 0, 0);
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142 for(i = 0; i < 256; ++i)
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145 b = fwd_affine(fi((aes_08t)i));
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146 w = bytes2word(f2(b), b, b, f3(b));
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149 t_set(s,box)[i] = b;
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152 #ifdef FT1_SET /* tables for a normal encryption round */
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156 t_set(f,n)[0][i] = w;
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157 t_set(f,n)[1][i] = upr(w,1);
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158 t_set(f,n)[2][i] = upr(w,2);
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159 t_set(f,n)[3][i] = upr(w,3);
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161 w = bytes2word(b, 0, 0, 0);
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163 #ifdef FL1_SET /* tables for last encryption round (may also */
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164 t_set(f,l)[i] = w; /* be used in the key schedule) */
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167 t_set(f,l)[0][i] = w;
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168 t_set(f,l)[1][i] = upr(w,1);
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169 t_set(f,l)[2][i] = upr(w,2);
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170 t_set(f,l)[3][i] = upr(w,3);
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173 #ifdef LS1_SET /* table for key schedule if t_set(f,l) above is */
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174 t_set(l,s)[i] = w; /* not of the required form */
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177 t_set(l,s)[0][i] = w;
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178 t_set(l,s)[1][i] = upr(w,1);
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179 t_set(l,s)[2][i] = upr(w,2);
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180 t_set(l,s)[3][i] = upr(w,3);
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183 b = fi(inv_affine((aes_08t)i));
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184 w = bytes2word(fe(b), f9(b), fd(b), fb(b));
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186 #ifdef IM1_SET /* tables for the inverse mix column operation */
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190 t_set(i,m)[0][b] = w;
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191 t_set(i,m)[1][b] = upr(w,1);
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192 t_set(i,m)[2][b] = upr(w,2);
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193 t_set(i,m)[3][b] = upr(w,3);
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197 t_set(i,box)[i] = b;
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199 #ifdef IT1_SET /* tables for a normal decryption round */
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203 t_set(i,n)[0][i] = w;
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204 t_set(i,n)[1][i] = upr(w,1);
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205 t_set(i,n)[2][i] = upr(w,2);
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206 t_set(i,n)[3][i] = upr(w,3);
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208 w = bytes2word(b, 0, 0, 0);
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209 #ifdef IL1_SET /* tables for last decryption round */
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213 t_set(i,l)[0][i] = w;
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214 t_set(i,l)[1][i] = upr(w,1);
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215 t_set(i,l)[2][i] = upr(w,2);
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216 t_set(i,l)[3][i] = upr(w,3);
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