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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
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2 * |
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3 * LibTomCrypt is a library that provides various cryptographic |
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4 * algorithms in a highly modular and flexible manner. |
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5 * |
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6 * The library is free for all purposes without any express |
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7 * guarantee it works. |
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8 * |
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9 * Tom St Denis, [email protected], http://libtomcrypt.org |
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10 */ |
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11 |
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12 #include "mycrypt.h" |
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13 |
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14 #ifdef XTEA |
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15 |
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16 const struct _cipher_descriptor xtea_desc = |
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17 { |
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18 "xtea", |
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19 1, |
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20 16, 16, 8, 32, |
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21 &xtea_setup, |
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22 &xtea_ecb_encrypt, |
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23 &xtea_ecb_decrypt, |
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24 &xtea_test, |
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25 &xtea_keysize |
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26 }; |
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27 |
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28 int xtea_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey) |
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29 { |
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30 unsigned long x, sum, K[4]; |
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31 |
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32 _ARGCHK(key != NULL); |
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33 _ARGCHK(skey != NULL); |
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34 |
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35 /* check arguments */ |
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36 if (keylen != 16) { |
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37 return CRYPT_INVALID_KEYSIZE; |
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38 } |
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39 |
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40 if (num_rounds != 0 && num_rounds != 32) { |
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41 return CRYPT_INVALID_ROUNDS; |
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42 } |
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43 |
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44 /* load key */ |
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45 LOAD32L(K[0], key+0); |
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46 LOAD32L(K[1], key+4); |
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47 LOAD32L(K[2], key+8); |
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48 LOAD32L(K[3], key+12); |
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49 |
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50 for (x = sum = 0; x < 32; x++) { |
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51 skey->xtea.A[x] = (sum + K[sum&3]) & 0xFFFFFFFFUL; |
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52 sum = (sum + 0x9E3779B9UL) & 0xFFFFFFFFUL; |
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53 skey->xtea.B[x] = (sum + K[(sum>>11)&3]) & 0xFFFFFFFFUL; |
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54 } |
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55 |
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56 #ifdef CLEAN_STACK |
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57 zeromem(&K, sizeof(K)); |
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58 #endif |
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59 |
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60 return CRYPT_OK; |
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61 } |
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62 |
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63 void xtea_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *key) |
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64 { |
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65 unsigned long y, z; |
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66 int r; |
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67 |
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68 _ARGCHK(pt != NULL); |
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69 _ARGCHK(ct != NULL); |
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70 _ARGCHK(key != NULL); |
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71 |
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72 LOAD32L(y, &pt[0]); |
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73 LOAD32L(z, &pt[4]); |
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74 for (r = 0; r < 32; r += 4) { |
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75 y = (y + ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r])) & 0xFFFFFFFFUL; |
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76 z = (z + ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r])) & 0xFFFFFFFFUL; |
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77 |
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78 y = (y + ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r+1])) & 0xFFFFFFFFUL; |
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79 z = (z + ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r+1])) & 0xFFFFFFFFUL; |
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80 |
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81 y = (y + ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r+2])) & 0xFFFFFFFFUL; |
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82 z = (z + ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r+2])) & 0xFFFFFFFFUL; |
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83 |
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84 y = (y + ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r+3])) & 0xFFFFFFFFUL; |
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85 z = (z + ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r+3])) & 0xFFFFFFFFUL; |
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86 } |
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87 STORE32L(y, &ct[0]); |
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88 STORE32L(z, &ct[4]); |
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89 } |
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90 |
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91 void xtea_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *key) |
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92 { |
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93 unsigned long y, z; |
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94 int r; |
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95 |
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96 _ARGCHK(pt != NULL); |
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97 _ARGCHK(ct != NULL); |
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98 _ARGCHK(key != NULL); |
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99 |
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100 LOAD32L(y, &ct[0]); |
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101 LOAD32L(z, &ct[4]); |
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102 for (r = 31; r >= 0; r -= 4) { |
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103 z = (z - ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r])) & 0xFFFFFFFFUL; |
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104 y = (y - ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r])) & 0xFFFFFFFFUL; |
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105 |
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106 z = (z - ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r-1])) & 0xFFFFFFFFUL; |
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107 y = (y - ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r-1])) & 0xFFFFFFFFUL; |
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108 |
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109 z = (z - ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r-2])) & 0xFFFFFFFFUL; |
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110 y = (y - ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r-2])) & 0xFFFFFFFFUL; |
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111 |
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112 z = (z - ((((y<<4)^(y>>5)) + y) ^ key->xtea.B[r-3])) & 0xFFFFFFFFUL; |
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113 y = (y - ((((z<<4)^(z>>5)) + z) ^ key->xtea.A[r-3])) & 0xFFFFFFFFUL; |
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114 } |
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115 STORE32L(y, &pt[0]); |
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116 STORE32L(z, &pt[4]); |
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117 } |
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118 |
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119 int xtea_test(void) |
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120 { |
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121 #ifndef LTC_TEST |
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122 return CRYPT_NOP; |
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123 #else |
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124 static const unsigned char key[16] = |
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125 { 0x78, 0x56, 0x34, 0x12, 0xf0, 0xcd, 0xcb, 0x9a, |
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126 0x48, 0x37, 0x26, 0x15, 0xc0, 0xbf, 0xae, 0x9d }; |
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127 static const unsigned char pt[8] = |
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128 { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 }; |
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129 static const unsigned char ct[8] = |
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130 { 0x75, 0xd7, 0xc5, 0xbf, 0xcf, 0x58, 0xc9, 0x3f }; |
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131 unsigned char tmp[2][8]; |
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132 symmetric_key skey; |
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133 int err, y; |
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134 |
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135 if ((err = xtea_setup(key, 16, 0, &skey)) != CRYPT_OK) { |
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136 return err; |
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137 } |
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138 xtea_ecb_encrypt(pt, tmp[0], &skey); |
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139 xtea_ecb_decrypt(tmp[0], tmp[1], &skey); |
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140 |
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141 if (memcmp(tmp[0], ct, 8) != 0 || memcmp(tmp[1], pt, 8) != 0) { |
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142 return CRYPT_FAIL_TESTVECTOR; |
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143 } |
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144 |
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145 /* now see if we can encrypt all zero bytes 1000 times, decrypt and come back where we started */ |
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146 for (y = 0; y < 8; y++) tmp[0][y] = 0; |
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147 for (y = 0; y < 1000; y++) xtea_ecb_encrypt(tmp[0], tmp[0], &skey); |
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148 for (y = 0; y < 1000; y++) xtea_ecb_decrypt(tmp[0], tmp[0], &skey); |
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149 for (y = 0; y < 8; y++) if (tmp[0][y] != 0) return CRYPT_FAIL_TESTVECTOR; |
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150 |
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151 return CRYPT_OK; |
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152 #endif |
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153 } |
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154 |
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155 int xtea_keysize(int *desired_keysize) |
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156 { |
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157 _ARGCHK(desired_keysize != NULL); |
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158 if (*desired_keysize < 16) { |
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159 return CRYPT_INVALID_KEYSIZE; |
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160 } |
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161 *desired_keysize = 16; |
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162 return CRYPT_OK; |
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163 } |
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164 |
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165 |
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166 #endif |
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167 |
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168 |
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169 |
