cipher.c (5424B)
1 /* 2 Implementation of the Lilliput-AE tweakable block cipher. 3 4 Authors, hereby denoted as "the implementer": 5 Kévin Le Gouguec, 6 2019. 7 8 For more information, feedback or questions, refer to our website: 9 https://paclido.fr/lilliput-ae 10 11 To the extent possible under law, the implementer has waived all copyright 12 and related or neighboring rights to the source code in this file. 13 http://creativecommons.org/publicdomain/zero/1.0/ 14 15 --- 16 17 This file provides an implementation for Lilliput-TBC where the encryption 18 process generates sub-tweakeys on the fly for each round. This saves on RAM 19 since it avoids storing all subtweakeys. 20 */ 21 22 #include <stdint.h> 23 #include <string.h> 24 25 #include "cipher.h" 26 #include "constants.h" 27 #include "tweakey.h" 28 29 30 enum permutation 31 { 32 PERMUTATION_ENCRYPTION = 0, /* PI(i) */ 33 PERMUTATION_DECRYPTION = 1, /* PI^-1(i) */ 34 PERMUTATION_NONE 35 }; 36 37 typedef enum permutation permutation; 38 39 static const uint8_t PERMUTATIONS[2][BLOCK_BYTES] = { 40 [PERMUTATION_ENCRYPTION] = { 13, 9, 14, 8, 10, 11, 12, 15, 4, 5, 3, 1, 2, 6, 0, 7 }, 41 [PERMUTATION_DECRYPTION] = { 14, 11, 12, 10, 8, 9, 13, 15, 3, 1, 4, 5, 6, 0, 2, 7 } 42 }; 43 44 static const uint8_t S[256] = { 45 0x20, 0x00, 0xB2, 0x85, 0x3B, 0x35, 0xA6, 0xA4, 0x30, 0xE4, 0x6A, 0x2C, 0xFF, 0x59, 0xE2, 0x0E, 46 0xF8, 0x1E, 0x7A, 0x80, 0x15, 0xBD, 0x3E, 0xB1, 0xE8, 0xF3, 0xA2, 0xC2, 0xDA, 0x51, 0x2A, 0x10, 47 0x21, 0x01, 0x23, 0x78, 0x5C, 0x24, 0x27, 0xB5, 0x37, 0xC7, 0x2B, 0x1F, 0xAE, 0x0A, 0x77, 0x5F, 48 0x6F, 0x09, 0x9D, 0x81, 0x04, 0x5A, 0x29, 0xDC, 0x39, 0x9C, 0x05, 0x57, 0x97, 0x74, 0x79, 0x17, 49 0x44, 0xC6, 0xE6, 0xE9, 0xDD, 0x41, 0xF2, 0x8A, 0x54, 0xCA, 0x6E, 0x4A, 0xE1, 0xAD, 0xB6, 0x88, 50 0x1C, 0x98, 0x7E, 0xCE, 0x63, 0x49, 0x3A, 0x5D, 0x0C, 0xEF, 0xF6, 0x34, 0x56, 0x25, 0x2E, 0xD6, 51 0x67, 0x75, 0x55, 0x76, 0xB8, 0xD2, 0x61, 0xD9, 0x71, 0x8B, 0xCD, 0x0B, 0x72, 0x6C, 0x31, 0x4B, 52 0x69, 0xFD, 0x7B, 0x6D, 0x60, 0x3C, 0x2F, 0x62, 0x3F, 0x22, 0x73, 0x13, 0xC9, 0x82, 0x7F, 0x53, 53 0x32, 0x12, 0xA0, 0x7C, 0x02, 0x87, 0x84, 0x86, 0x93, 0x4E, 0x68, 0x46, 0x8D, 0xC3, 0xDB, 0xEC, 54 0x9B, 0xB7, 0x89, 0x92, 0xA7, 0xBE, 0x3D, 0xD8, 0xEA, 0x50, 0x91, 0xF1, 0x33, 0x38, 0xE0, 0xA9, 55 0xA3, 0x83, 0xA1, 0x1B, 0xCF, 0x06, 0x95, 0x07, 0x9E, 0xED, 0xB9, 0xF5, 0x4C, 0xC0, 0xF4, 0x2D, 56 0x16, 0xFA, 0xB4, 0x03, 0x26, 0xB3, 0x90, 0x4F, 0xAB, 0x65, 0xFC, 0xFE, 0x14, 0xF7, 0xE3, 0x94, 57 0xEE, 0xAC, 0x8C, 0x1A, 0xDE, 0xCB, 0x28, 0x40, 0x7D, 0xC8, 0xC4, 0x48, 0x6B, 0xDF, 0xA5, 0x52, 58 0xE5, 0xFB, 0xD7, 0x64, 0xF9, 0xF0, 0xD3, 0x5E, 0x66, 0x96, 0x8F, 0x1D, 0x45, 0x36, 0xCC, 0xC5, 59 0x4D, 0x9F, 0xBF, 0x0F, 0xD1, 0x08, 0xEB, 0x43, 0x42, 0x19, 0xE7, 0x99, 0xA8, 0x8E, 0x58, 0xC1, 60 0x9A, 0xD4, 0x18, 0x47, 0xAA, 0xAF, 0xBC, 0x5B, 0xD5, 0x11, 0xD0, 0xB0, 0x70, 0xBB, 0x0D, 0xBA 61 }; 62 63 64 static void _state_init(uint8_t X[BLOCK_BYTES], const uint8_t message[BLOCK_BYTES]) 65 { 66 memcpy(X, message, BLOCK_BYTES); 67 } 68 69 70 static void _compute_round_tweakeys( 71 const uint8_t key[KEY_BYTES], 72 const uint8_t tweak[TWEAK_BYTES], 73 uint8_t RTK[ROUNDS][ROUND_TWEAKEY_BYTES] 74 ) 75 { 76 uint8_t TK[TWEAKEY_BYTES]; 77 tweakey_state_init(TK, key, tweak); 78 tweakey_state_extract(TK, 0, RTK[0]); 79 80 for (size_t i=1; i<ROUNDS; i++) 81 { 82 tweakey_state_update(TK); 83 tweakey_state_extract(TK, i, RTK[i]); 84 } 85 } 86 87 88 static uint8_t _Fj(uint8_t Xj, uint8_t RTKj) 89 { 90 return S[Xj ^ RTKj]; 91 } 92 93 static void _nonlinear_layer(uint8_t X[BLOCK_BYTES], const uint8_t RTK[ROUND_TWEAKEY_BYTES]) 94 { 95 for (size_t j=0; j<8; j++) 96 { 97 X[15-j] ^= _Fj(X[j], RTK[j]); 98 } 99 } 100 101 static void _linear_layer(uint8_t X[BLOCK_BYTES]) 102 { 103 for (size_t j=1; j<8; j++) 104 { 105 X[15] ^= X[j]; 106 } 107 108 for (size_t j=14; j>8; j--) 109 { 110 X[j] ^= X[7]; 111 } 112 } 113 114 static void _permutation_layer(uint8_t X[BLOCK_BYTES], permutation p) 115 { 116 if (p == PERMUTATION_NONE) 117 { 118 return; 119 } 120 121 uint8_t X_old[BLOCK_BYTES]; 122 memcpy(X_old, X, BLOCK_BYTES); 123 124 const uint8_t *pi = PERMUTATIONS[p]; 125 126 for (size_t j=0; j<BLOCK_BYTES; j++) 127 { 128 X[pi[j]] = X_old[j]; 129 } 130 } 131 132 static void _one_round_egfn(uint8_t X[BLOCK_BYTES], const uint8_t RTK[ROUND_TWEAKEY_BYTES], permutation p) 133 { 134 _nonlinear_layer(X, RTK); 135 _linear_layer(X); 136 _permutation_layer(X, p); 137 } 138 139 140 void lilliput_tbc_encrypt( 141 const uint8_t key[KEY_BYTES], 142 const uint8_t tweak[TWEAK_BYTES], 143 const uint8_t message[BLOCK_BYTES], 144 uint8_t ciphertext[BLOCK_BYTES] 145 ) 146 { 147 _state_init(ciphertext, message); 148 149 uint8_t TK[TWEAKEY_BYTES]; 150 uint8_t RTK[ROUND_TWEAKEY_BYTES]; 151 tweakey_state_init(TK, key, tweak); 152 153 for (size_t i=0; i<ROUNDS-1; i++) 154 { 155 tweakey_state_extract(TK, i, RTK); 156 _one_round_egfn(ciphertext, RTK, PERMUTATION_ENCRYPTION); 157 tweakey_state_update(TK); 158 } 159 160 tweakey_state_extract(TK, ROUNDS-1, RTK); 161 _one_round_egfn(ciphertext, RTK, PERMUTATION_NONE); 162 } 163 164 void lilliput_tbc_decrypt( 165 const uint8_t key[KEY_BYTES], 166 const uint8_t tweak[TWEAK_BYTES], 167 const uint8_t ciphertext[BLOCK_BYTES], 168 uint8_t message[BLOCK_BYTES] 169 ) 170 { 171 _state_init(message, ciphertext); 172 173 uint8_t RTK[ROUNDS][ROUND_TWEAKEY_BYTES]; 174 _compute_round_tweakeys(key, tweak, RTK); 175 176 for (size_t i=0; i<ROUNDS-1; i++) 177 { 178 _one_round_egfn(message, RTK[ROUNDS-1-i], PERMUTATION_DECRYPTION); 179 } 180 181 _one_round_egfn(message, RTK[0], PERMUTATION_NONE); 182 }