1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */ 2 /* SPDX-License-Identifier: Unlicense */ 3 4 /** 5 @file skipjack.c 6 Skipjack Implementation by Tom St Denis 7 */ 8 #include "tomcrypt_private.h" 9 10 #ifdef LTC_SKIPJACK 11 12 const struct ltc_cipher_descriptor skipjack_desc = 13 { 14 "skipjack", 15 17, 16 10, 10, 8, 32, 17 &skipjack_setup, 18 &skipjack_ecb_encrypt, 19 &skipjack_ecb_decrypt, 20 &skipjack_test, 21 &skipjack_done, 22 &skipjack_keysize, 23 NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL 24 }; 25 26 static const unsigned char sbox[256] = { 27 0xa3,0xd7,0x09,0x83,0xf8,0x48,0xf6,0xf4,0xb3,0x21,0x15,0x78,0x99,0xb1,0xaf,0xf9, 28 0xe7,0x2d,0x4d,0x8a,0xce,0x4c,0xca,0x2e,0x52,0x95,0xd9,0x1e,0x4e,0x38,0x44,0x28, 29 0x0a,0xdf,0x02,0xa0,0x17,0xf1,0x60,0x68,0x12,0xb7,0x7a,0xc3,0xe9,0xfa,0x3d,0x53, 30 0x96,0x84,0x6b,0xba,0xf2,0x63,0x9a,0x19,0x7c,0xae,0xe5,0xf5,0xf7,0x16,0x6a,0xa2, 31 0x39,0xb6,0x7b,0x0f,0xc1,0x93,0x81,0x1b,0xee,0xb4,0x1a,0xea,0xd0,0x91,0x2f,0xb8, 32 0x55,0xb9,0xda,0x85,0x3f,0x41,0xbf,0xe0,0x5a,0x58,0x80,0x5f,0x66,0x0b,0xd8,0x90, 33 0x35,0xd5,0xc0,0xa7,0x33,0x06,0x65,0x69,0x45,0x00,0x94,0x56,0x6d,0x98,0x9b,0x76, 34 0x97,0xfc,0xb2,0xc2,0xb0,0xfe,0xdb,0x20,0xe1,0xeb,0xd6,0xe4,0xdd,0x47,0x4a,0x1d, 35 0x42,0xed,0x9e,0x6e,0x49,0x3c,0xcd,0x43,0x27,0xd2,0x07,0xd4,0xde,0xc7,0x67,0x18, 36 0x89,0xcb,0x30,0x1f,0x8d,0xc6,0x8f,0xaa,0xc8,0x74,0xdc,0xc9,0x5d,0x5c,0x31,0xa4, 37 0x70,0x88,0x61,0x2c,0x9f,0x0d,0x2b,0x87,0x50,0x82,0x54,0x64,0x26,0x7d,0x03,0x40, 38 0x34,0x4b,0x1c,0x73,0xd1,0xc4,0xfd,0x3b,0xcc,0xfb,0x7f,0xab,0xe6,0x3e,0x5b,0xa5, 39 0xad,0x04,0x23,0x9c,0x14,0x51,0x22,0xf0,0x29,0x79,0x71,0x7e,0xff,0x8c,0x0e,0xe2, 40 0x0c,0xef,0xbc,0x72,0x75,0x6f,0x37,0xa1,0xec,0xd3,0x8e,0x62,0x8b,0x86,0x10,0xe8, 41 0x08,0x77,0x11,0xbe,0x92,0x4f,0x24,0xc5,0x32,0x36,0x9d,0xcf,0xf3,0xa6,0xbb,0xac, 42 0x5e,0x6c,0xa9,0x13,0x57,0x25,0xb5,0xe3,0xbd,0xa8,0x3a,0x01,0x05,0x59,0x2a,0x46 43 }; 44 45 /* simple x + 1 (mod 10) in one step. */ 46 static const int keystep[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 }; 47 48 /* simple x - 1 (mod 10) in one step */ 49 static const int ikeystep[] = { 9, 0, 1, 2, 3, 4, 5, 6, 7, 8 }; 50 51 /** 52 Initialize the Skipjack block cipher 53 @param key The symmetric key you wish to pass 54 @param keylen The key length in bytes 55 @param num_rounds The number of rounds desired (0 for default) 56 @param skey The key in as scheduled by this function. 57 @return CRYPT_OK if successful 58 */ 59 int skipjack_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey) 60 { 61 int x; 62 63 LTC_ARGCHK(key != NULL); 64 LTC_ARGCHK(skey != NULL); 65 66 if (keylen != 10) { 67 return CRYPT_INVALID_KEYSIZE; 68 } 69 70 if (num_rounds != 32 && num_rounds != 0) { 71 return CRYPT_INVALID_ROUNDS; 72 } 73 74 /* make sure the key is in range for platforms where CHAR_BIT != 8 */ 75 for (x = 0; x < 10; x++) { 76 skey->skipjack.key[x] = key[x] & 255; 77 } 78 79 return CRYPT_OK; 80 } 81 82 #define RULE_A \ 83 tmp = g_func(w1, &kp, skey->skipjack.key); \ 84 w1 = tmp ^ w4 ^ x; \ 85 w4 = w3; w3 = w2; \ 86 w2 = tmp; 87 88 #define RULE_B \ 89 tmp = g_func(w1, &kp, skey->skipjack.key); \ 90 tmp1 = w4; w4 = w3; \ 91 w3 = w1 ^ w2 ^ x; \ 92 w1 = tmp1; w2 = tmp; 93 94 #define RULE_A1 \ 95 tmp = w1 ^ w2 ^ x; \ 96 w1 = ig_func(w2, &kp, skey->skipjack.key); \ 97 w2 = w3; w3 = w4; w4 = tmp; 98 99 #define RULE_B1 \ 100 tmp = ig_func(w2, &kp, skey->skipjack.key); \ 101 w2 = tmp ^ w3 ^ x; \ 102 w3 = w4; w4 = w1; w1 = tmp; 103 104 static unsigned g_func(unsigned w, int *kp, const unsigned char *key) 105 { 106 unsigned char g1,g2; 107 108 g1 = (w >> 8) & 255; g2 = w & 255; 109 g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp]; 110 g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp]; 111 g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp]; 112 g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp]; 113 return ((unsigned)g1<<8)|(unsigned)g2; 114 } 115 116 static unsigned ig_func(unsigned w, int *kp, const unsigned char *key) 117 { 118 unsigned char g1,g2; 119 120 g1 = (w >> 8) & 255; g2 = w & 255; 121 *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]]; 122 *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]]; 123 *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]]; 124 *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]]; 125 return ((unsigned)g1<<8)|(unsigned)g2; 126 } 127 128 /** 129 Encrypts a block of text with Skipjack 130 @param pt The input plaintext (8 bytes) 131 @param ct The output ciphertext (8 bytes) 132 @param skey The key as scheduled 133 @return CRYPT_OK if successful 134 */ 135 #ifdef LTC_CLEAN_STACK 136 static int s_skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, const symmetric_key *skey) 137 #else 138 int skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, const symmetric_key *skey) 139 #endif 140 { 141 unsigned w1,w2,w3,w4,tmp,tmp1; 142 int x, kp; 143 144 LTC_ARGCHK(pt != NULL); 145 LTC_ARGCHK(ct != NULL); 146 LTC_ARGCHK(skey != NULL); 147 148 /* load block */ 149 w1 = ((unsigned)pt[0]<<8)|pt[1]; 150 w2 = ((unsigned)pt[2]<<8)|pt[3]; 151 w3 = ((unsigned)pt[4]<<8)|pt[5]; 152 w4 = ((unsigned)pt[6]<<8)|pt[7]; 153 154 /* 8 rounds of RULE A */ 155 for (x = 1, kp = 0; x < 9; x++) { 156 RULE_A; 157 } 158 159 /* 8 rounds of RULE B */ 160 for (; x < 17; x++) { 161 RULE_B; 162 } 163 164 /* 8 rounds of RULE A */ 165 for (; x < 25; x++) { 166 RULE_A; 167 } 168 169 /* 8 rounds of RULE B */ 170 for (; x < 33; x++) { 171 RULE_B; 172 } 173 174 /* store block */ 175 ct[0] = (w1>>8)&255; ct[1] = w1&255; 176 ct[2] = (w2>>8)&255; ct[3] = w2&255; 177 ct[4] = (w3>>8)&255; ct[5] = w3&255; 178 ct[6] = (w4>>8)&255; ct[7] = w4&255; 179 180 return CRYPT_OK; 181 } 182 183 #ifdef LTC_CLEAN_STACK 184 int skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, const symmetric_key *skey) 185 { 186 int err = s_skipjack_ecb_encrypt(pt, ct, skey); 187 burn_stack(sizeof(unsigned) * 8 + sizeof(int) * 2); 188 return err; 189 } 190 #endif 191 192 /** 193 Decrypts a block of text with Skipjack 194 @param ct The input ciphertext (8 bytes) 195 @param pt The output plaintext (8 bytes) 196 @param skey The key as scheduled 197 @return CRYPT_OK if successful 198 */ 199 #ifdef LTC_CLEAN_STACK 200 static int s_skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, const symmetric_key *skey) 201 #else 202 int skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, const symmetric_key *skey) 203 #endif 204 { 205 unsigned w1,w2,w3,w4,tmp; 206 int x, kp; 207 208 LTC_ARGCHK(pt != NULL); 209 LTC_ARGCHK(ct != NULL); 210 LTC_ARGCHK(skey != NULL); 211 212 /* load block */ 213 w1 = ((unsigned)ct[0]<<8)|ct[1]; 214 w2 = ((unsigned)ct[2]<<8)|ct[3]; 215 w3 = ((unsigned)ct[4]<<8)|ct[5]; 216 w4 = ((unsigned)ct[6]<<8)|ct[7]; 217 218 /* 8 rounds of RULE B^-1 219 220 Note the value "kp = 8" comes from "kp = (32 * 4) mod 10" where 32*4 is 128 which mod 10 is 8 221 */ 222 for (x = 32, kp = 8; x > 24; x--) { 223 RULE_B1; 224 } 225 226 /* 8 rounds of RULE A^-1 */ 227 for (; x > 16; x--) { 228 RULE_A1; 229 } 230 231 232 /* 8 rounds of RULE B^-1 */ 233 for (; x > 8; x--) { 234 RULE_B1; 235 } 236 237 /* 8 rounds of RULE A^-1 */ 238 for (; x > 0; x--) { 239 RULE_A1; 240 } 241 242 /* store block */ 243 pt[0] = (w1>>8)&255; pt[1] = w1&255; 244 pt[2] = (w2>>8)&255; pt[3] = w2&255; 245 pt[4] = (w3>>8)&255; pt[5] = w3&255; 246 pt[6] = (w4>>8)&255; pt[7] = w4&255; 247 248 return CRYPT_OK; 249 } 250 251 #ifdef LTC_CLEAN_STACK 252 int skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, const symmetric_key *skey) 253 { 254 int err = s_skipjack_ecb_decrypt(ct, pt, skey); 255 burn_stack(sizeof(unsigned) * 7 + sizeof(int) * 2); 256 return err; 257 } 258 #endif 259 260 /** 261 Performs a self-test of the Skipjack block cipher 262 @return CRYPT_OK if functional, CRYPT_NOP if self-test has been disabled 263 */ 264 int skipjack_test(void) 265 { 266 #ifndef LTC_TEST 267 return CRYPT_NOP; 268 #else 269 static const struct { 270 unsigned char key[10], pt[8], ct[8]; 271 } tests[] = { 272 { 273 { 0x00, 0x99, 0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11 }, 274 { 0x33, 0x22, 0x11, 0x00, 0xdd, 0xcc, 0xbb, 0xaa }, 275 { 0x25, 0x87, 0xca, 0xe2, 0x7a, 0x12, 0xd3, 0x00 } 276 } 277 }; 278 unsigned char buf[2][8]; 279 int x, y, err; 280 symmetric_key key; 281 282 for (x = 0; x < (int)(sizeof(tests) / sizeof(tests[0])); x++) { 283 /* setup key */ 284 if ((err = skipjack_setup(tests[x].key, 10, 0, &key)) != CRYPT_OK) { 285 return err; 286 } 287 288 /* encrypt and decrypt */ 289 skipjack_ecb_encrypt(tests[x].pt, buf[0], &key); 290 skipjack_ecb_decrypt(buf[0], buf[1], &key); 291 292 /* compare */ 293 if (compare_testvector(buf[0], 8, tests[x].ct, 8, "Skipjack Encrypt", x) != 0 || 294 compare_testvector(buf[1], 8, tests[x].pt, 8, "Skipjack Decrypt", x) != 0) { 295 return CRYPT_FAIL_TESTVECTOR; 296 } 297 298 /* now see if we can encrypt all zero bytes 1000 times, decrypt and come back where we started */ 299 for (y = 0; y < 8; y++) buf[0][y] = 0; 300 for (y = 0; y < 1000; y++) skipjack_ecb_encrypt(buf[0], buf[0], &key); 301 for (y = 0; y < 1000; y++) skipjack_ecb_decrypt(buf[0], buf[0], &key); 302 for (y = 0; y < 8; y++) if (buf[0][y] != 0) return CRYPT_FAIL_TESTVECTOR; 303 } 304 305 return CRYPT_OK; 306 #endif 307 } 308 309 /** Terminate the context 310 @param skey The scheduled key 311 */ 312 void skipjack_done(symmetric_key *skey) 313 { 314 LTC_UNUSED_PARAM(skey); 315 } 316 317 /** 318 Gets suitable key size 319 @param keysize [in/out] The length of the recommended key (in bytes). This function will store the suitable size back in this variable. 320 @return CRYPT_OK if the input key size is acceptable. 321 */ 322 int skipjack_keysize(int *keysize) 323 { 324 LTC_ARGCHK(keysize != NULL); 325 if (*keysize < 10) { 326 return CRYPT_INVALID_KEYSIZE; 327 } 328 if (*keysize > 10) { 329 *keysize = 10; 330 } 331 return CRYPT_OK; 332 } 333 334 #endif 335