1 // SPDX-License-Identifier: BSD-2-Clause 2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis 3 * 4 * LibTomCrypt is a library that provides various cryptographic 5 * algorithms in a highly modular and flexible manner. 6 * 7 * The library is free for all purposes without any express 8 * guarantee it works. 9 */ 10 11 /** 12 @file skipjack.c 13 Skipjack Implementation by Tom St Denis 14 */ 15 #include "tomcrypt_private.h" 16 17 #ifdef LTC_SKIPJACK 18 19 const struct ltc_cipher_descriptor skipjack_desc = 20 { 21 "skipjack", 22 17, 23 10, 10, 8, 32, 24 &skipjack_setup, 25 &skipjack_ecb_encrypt, 26 &skipjack_ecb_decrypt, 27 &skipjack_test, 28 &skipjack_done, 29 &skipjack_keysize, 30 NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL 31 }; 32 33 static const unsigned char sbox[256] = { 34 0xa3,0xd7,0x09,0x83,0xf8,0x48,0xf6,0xf4,0xb3,0x21,0x15,0x78,0x99,0xb1,0xaf,0xf9, 35 0xe7,0x2d,0x4d,0x8a,0xce,0x4c,0xca,0x2e,0x52,0x95,0xd9,0x1e,0x4e,0x38,0x44,0x28, 36 0x0a,0xdf,0x02,0xa0,0x17,0xf1,0x60,0x68,0x12,0xb7,0x7a,0xc3,0xe9,0xfa,0x3d,0x53, 37 0x96,0x84,0x6b,0xba,0xf2,0x63,0x9a,0x19,0x7c,0xae,0xe5,0xf5,0xf7,0x16,0x6a,0xa2, 38 0x39,0xb6,0x7b,0x0f,0xc1,0x93,0x81,0x1b,0xee,0xb4,0x1a,0xea,0xd0,0x91,0x2f,0xb8, 39 0x55,0xb9,0xda,0x85,0x3f,0x41,0xbf,0xe0,0x5a,0x58,0x80,0x5f,0x66,0x0b,0xd8,0x90, 40 0x35,0xd5,0xc0,0xa7,0x33,0x06,0x65,0x69,0x45,0x00,0x94,0x56,0x6d,0x98,0x9b,0x76, 41 0x97,0xfc,0xb2,0xc2,0xb0,0xfe,0xdb,0x20,0xe1,0xeb,0xd6,0xe4,0xdd,0x47,0x4a,0x1d, 42 0x42,0xed,0x9e,0x6e,0x49,0x3c,0xcd,0x43,0x27,0xd2,0x07,0xd4,0xde,0xc7,0x67,0x18, 43 0x89,0xcb,0x30,0x1f,0x8d,0xc6,0x8f,0xaa,0xc8,0x74,0xdc,0xc9,0x5d,0x5c,0x31,0xa4, 44 0x70,0x88,0x61,0x2c,0x9f,0x0d,0x2b,0x87,0x50,0x82,0x54,0x64,0x26,0x7d,0x03,0x40, 45 0x34,0x4b,0x1c,0x73,0xd1,0xc4,0xfd,0x3b,0xcc,0xfb,0x7f,0xab,0xe6,0x3e,0x5b,0xa5, 46 0xad,0x04,0x23,0x9c,0x14,0x51,0x22,0xf0,0x29,0x79,0x71,0x7e,0xff,0x8c,0x0e,0xe2, 47 0x0c,0xef,0xbc,0x72,0x75,0x6f,0x37,0xa1,0xec,0xd3,0x8e,0x62,0x8b,0x86,0x10,0xe8, 48 0x08,0x77,0x11,0xbe,0x92,0x4f,0x24,0xc5,0x32,0x36,0x9d,0xcf,0xf3,0xa6,0xbb,0xac, 49 0x5e,0x6c,0xa9,0x13,0x57,0x25,0xb5,0xe3,0xbd,0xa8,0x3a,0x01,0x05,0x59,0x2a,0x46 50 }; 51 52 /* simple x + 1 (mod 10) in one step. */ 53 static const int keystep[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 }; 54 55 /* simple x - 1 (mod 10) in one step */ 56 static const int ikeystep[] = { 9, 0, 1, 2, 3, 4, 5, 6, 7, 8 }; 57 58 /** 59 Initialize the Skipjack block cipher 60 @param key The symmetric key you wish to pass 61 @param keylen The key length in bytes 62 @param num_rounds The number of rounds desired (0 for default) 63 @param skey The key in as scheduled by this function. 64 @return CRYPT_OK if successful 65 */ 66 int skipjack_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey) 67 { 68 int x; 69 70 LTC_ARGCHK(key != NULL); 71 LTC_ARGCHK(skey != NULL); 72 73 if (keylen != 10) { 74 return CRYPT_INVALID_KEYSIZE; 75 } 76 77 if (num_rounds != 32 && num_rounds != 0) { 78 return CRYPT_INVALID_ROUNDS; 79 } 80 81 /* make sure the key is in range for platforms where CHAR_BIT != 8 */ 82 for (x = 0; x < 10; x++) { 83 skey->skipjack.key[x] = key[x] & 255; 84 } 85 86 return CRYPT_OK; 87 } 88 89 #define RULE_A \ 90 tmp = g_func(w1, &kp, skey->skipjack.key); \ 91 w1 = tmp ^ w4 ^ x; \ 92 w4 = w3; w3 = w2; \ 93 w2 = tmp; 94 95 #define RULE_B \ 96 tmp = g_func(w1, &kp, skey->skipjack.key); \ 97 tmp1 = w4; w4 = w3; \ 98 w3 = w1 ^ w2 ^ x; \ 99 w1 = tmp1; w2 = tmp; 100 101 #define RULE_A1 \ 102 tmp = w1 ^ w2 ^ x; \ 103 w1 = ig_func(w2, &kp, skey->skipjack.key); \ 104 w2 = w3; w3 = w4; w4 = tmp; 105 106 #define RULE_B1 \ 107 tmp = ig_func(w2, &kp, skey->skipjack.key); \ 108 w2 = tmp ^ w3 ^ x; \ 109 w3 = w4; w4 = w1; w1 = tmp; 110 111 static unsigned g_func(unsigned w, int *kp, const unsigned char *key) 112 { 113 unsigned char g1,g2; 114 115 g1 = (w >> 8) & 255; g2 = w & 255; 116 g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp]; 117 g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp]; 118 g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp]; 119 g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp]; 120 return ((unsigned)g1<<8)|(unsigned)g2; 121 } 122 123 static unsigned ig_func(unsigned w, int *kp, const unsigned char *key) 124 { 125 unsigned char g1,g2; 126 127 g1 = (w >> 8) & 255; g2 = w & 255; 128 *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]]; 129 *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]]; 130 *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]]; 131 *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]]; 132 return ((unsigned)g1<<8)|(unsigned)g2; 133 } 134 135 /** 136 Encrypts a block of text with Skipjack 137 @param pt The input plaintext (8 bytes) 138 @param ct The output ciphertext (8 bytes) 139 @param skey The key as scheduled 140 @return CRYPT_OK if successful 141 */ 142 #ifdef LTC_CLEAN_STACK 143 static int _skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, const symmetric_key *skey) 144 #else 145 int skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, const symmetric_key *skey) 146 #endif 147 { 148 unsigned w1,w2,w3,w4,tmp,tmp1; 149 int x, kp; 150 151 LTC_ARGCHK(pt != NULL); 152 LTC_ARGCHK(ct != NULL); 153 LTC_ARGCHK(skey != NULL); 154 155 /* load block */ 156 w1 = ((unsigned)pt[0]<<8)|pt[1]; 157 w2 = ((unsigned)pt[2]<<8)|pt[3]; 158 w3 = ((unsigned)pt[4]<<8)|pt[5]; 159 w4 = ((unsigned)pt[6]<<8)|pt[7]; 160 161 /* 8 rounds of RULE A */ 162 for (x = 1, kp = 0; x < 9; x++) { 163 RULE_A; 164 } 165 166 /* 8 rounds of RULE B */ 167 for (; x < 17; x++) { 168 RULE_B; 169 } 170 171 /* 8 rounds of RULE A */ 172 for (; x < 25; x++) { 173 RULE_A; 174 } 175 176 /* 8 rounds of RULE B */ 177 for (; x < 33; x++) { 178 RULE_B; 179 } 180 181 /* store block */ 182 ct[0] = (w1>>8)&255; ct[1] = w1&255; 183 ct[2] = (w2>>8)&255; ct[3] = w2&255; 184 ct[4] = (w3>>8)&255; ct[5] = w3&255; 185 ct[6] = (w4>>8)&255; ct[7] = w4&255; 186 187 return CRYPT_OK; 188 } 189 190 #ifdef LTC_CLEAN_STACK 191 int skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, const symmetric_key *skey) 192 { 193 int err = _skipjack_ecb_encrypt(pt, ct, skey); 194 burn_stack(sizeof(unsigned) * 8 + sizeof(int) * 2); 195 return err; 196 } 197 #endif 198 199 /** 200 Decrypts a block of text with Skipjack 201 @param ct The input ciphertext (8 bytes) 202 @param pt The output plaintext (8 bytes) 203 @param skey The key as scheduled 204 @return CRYPT_OK if successful 205 */ 206 #ifdef LTC_CLEAN_STACK 207 static int _skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, const symmetric_key *skey) 208 #else 209 int skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, const symmetric_key *skey) 210 #endif 211 { 212 unsigned w1,w2,w3,w4,tmp; 213 int x, kp; 214 215 LTC_ARGCHK(pt != NULL); 216 LTC_ARGCHK(ct != NULL); 217 LTC_ARGCHK(skey != NULL); 218 219 /* load block */ 220 w1 = ((unsigned)ct[0]<<8)|ct[1]; 221 w2 = ((unsigned)ct[2]<<8)|ct[3]; 222 w3 = ((unsigned)ct[4]<<8)|ct[5]; 223 w4 = ((unsigned)ct[6]<<8)|ct[7]; 224 225 /* 8 rounds of RULE B^-1 226 227 Note the value "kp = 8" comes from "kp = (32 * 4) mod 10" where 32*4 is 128 which mod 10 is 8 228 */ 229 for (x = 32, kp = 8; x > 24; x--) { 230 RULE_B1; 231 } 232 233 /* 8 rounds of RULE A^-1 */ 234 for (; x > 16; x--) { 235 RULE_A1; 236 } 237 238 239 /* 8 rounds of RULE B^-1 */ 240 for (; x > 8; x--) { 241 RULE_B1; 242 } 243 244 /* 8 rounds of RULE A^-1 */ 245 for (; x > 0; x--) { 246 RULE_A1; 247 } 248 249 /* store block */ 250 pt[0] = (w1>>8)&255; pt[1] = w1&255; 251 pt[2] = (w2>>8)&255; pt[3] = w2&255; 252 pt[4] = (w3>>8)&255; pt[5] = w3&255; 253 pt[6] = (w4>>8)&255; pt[7] = w4&255; 254 255 return CRYPT_OK; 256 } 257 258 #ifdef LTC_CLEAN_STACK 259 int skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, const symmetric_key *skey) 260 { 261 int err = _skipjack_ecb_decrypt(ct, pt, skey); 262 burn_stack(sizeof(unsigned) * 7 + sizeof(int) * 2); 263 return err; 264 } 265 #endif 266 267 /** 268 Performs a self-test of the Skipjack block cipher 269 @return CRYPT_OK if functional, CRYPT_NOP if self-test has been disabled 270 */ 271 int skipjack_test(void) 272 { 273 #ifndef LTC_TEST 274 return CRYPT_NOP; 275 #else 276 static const struct { 277 unsigned char key[10], pt[8], ct[8]; 278 } tests[] = { 279 { 280 { 0x00, 0x99, 0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11 }, 281 { 0x33, 0x22, 0x11, 0x00, 0xdd, 0xcc, 0xbb, 0xaa }, 282 { 0x25, 0x87, 0xca, 0xe2, 0x7a, 0x12, 0xd3, 0x00 } 283 } 284 }; 285 unsigned char buf[2][8]; 286 int x, y, err; 287 symmetric_key key; 288 289 for (x = 0; x < (int)(sizeof(tests) / sizeof(tests[0])); x++) { 290 /* setup key */ 291 if ((err = skipjack_setup(tests[x].key, 10, 0, &key)) != CRYPT_OK) { 292 return err; 293 } 294 295 /* encrypt and decrypt */ 296 skipjack_ecb_encrypt(tests[x].pt, buf[0], &key); 297 skipjack_ecb_decrypt(buf[0], buf[1], &key); 298 299 /* compare */ 300 if (compare_testvector(buf[0], 8, tests[x].ct, 8, "Skipjack Encrypt", x) != 0 || 301 compare_testvector(buf[1], 8, tests[x].pt, 8, "Skipjack Decrypt", x) != 0) { 302 return CRYPT_FAIL_TESTVECTOR; 303 } 304 305 /* now see if we can encrypt all zero bytes 1000 times, decrypt and come back where we started */ 306 for (y = 0; y < 8; y++) buf[0][y] = 0; 307 for (y = 0; y < 1000; y++) skipjack_ecb_encrypt(buf[0], buf[0], &key); 308 for (y = 0; y < 1000; y++) skipjack_ecb_decrypt(buf[0], buf[0], &key); 309 for (y = 0; y < 8; y++) if (buf[0][y] != 0) return CRYPT_FAIL_TESTVECTOR; 310 } 311 312 return CRYPT_OK; 313 #endif 314 } 315 316 /** Terminate the context 317 @param skey The scheduled key 318 */ 319 void skipjack_done(symmetric_key *skey) 320 { 321 LTC_UNUSED_PARAM(skey); 322 } 323 324 /** 325 Gets suitable key size 326 @param keysize [in/out] The length of the recommended key (in bytes). This function will store the suitable size back in this variable. 327 @return CRYPT_OK if the input key size is acceptable. 328 */ 329 int skipjack_keysize(int *keysize) 330 { 331 LTC_ARGCHK(keysize != NULL); 332 if (*keysize < 10) { 333 return CRYPT_INVALID_KEYSIZE; 334 } 335 if (*keysize > 10) { 336 *keysize = 10; 337 } 338 return CRYPT_OK; 339 } 340 341 #endif 342 343 /* ref: $Format:%D$ */ 344 /* git commit: $Format:%H$ */ 345 /* commit time: $Format:%ai$ */ 346