1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis 2 * 3 * LibTomCrypt is a library that provides various cryptographic 4 * algorithms in a highly modular and flexible manner. 5 * 6 * The library is free for all purposes without any express 7 * guarantee it works. 8 * 9 * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 12 /** 13 @file skipjack.c 14 Skipjack Implementation by Tom St Denis 15 */ 16 #include "tomcrypt.h" 17 18 #ifdef SKIPJACK 19 20 const struct ltc_cipher_descriptor skipjack_desc = 21 { 22 "skipjack", 23 17, 24 10, 10, 8, 32, 25 &skipjack_setup, 26 &skipjack_ecb_encrypt, 27 &skipjack_ecb_decrypt, 28 &skipjack_test, 29 &skipjack_done, 30 &skipjack_keysize, 31 NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL 32 }; 33 34 static const unsigned char sbox[256] = { 35 0xa3,0xd7,0x09,0x83,0xf8,0x48,0xf6,0xf4,0xb3,0x21,0x15,0x78,0x99,0xb1,0xaf,0xf9, 36 0xe7,0x2d,0x4d,0x8a,0xce,0x4c,0xca,0x2e,0x52,0x95,0xd9,0x1e,0x4e,0x38,0x44,0x28, 37 0x0a,0xdf,0x02,0xa0,0x17,0xf1,0x60,0x68,0x12,0xb7,0x7a,0xc3,0xe9,0xfa,0x3d,0x53, 38 0x96,0x84,0x6b,0xba,0xf2,0x63,0x9a,0x19,0x7c,0xae,0xe5,0xf5,0xf7,0x16,0x6a,0xa2, 39 0x39,0xb6,0x7b,0x0f,0xc1,0x93,0x81,0x1b,0xee,0xb4,0x1a,0xea,0xd0,0x91,0x2f,0xb8, 40 0x55,0xb9,0xda,0x85,0x3f,0x41,0xbf,0xe0,0x5a,0x58,0x80,0x5f,0x66,0x0b,0xd8,0x90, 41 0x35,0xd5,0xc0,0xa7,0x33,0x06,0x65,0x69,0x45,0x00,0x94,0x56,0x6d,0x98,0x9b,0x76, 42 0x97,0xfc,0xb2,0xc2,0xb0,0xfe,0xdb,0x20,0xe1,0xeb,0xd6,0xe4,0xdd,0x47,0x4a,0x1d, 43 0x42,0xed,0x9e,0x6e,0x49,0x3c,0xcd,0x43,0x27,0xd2,0x07,0xd4,0xde,0xc7,0x67,0x18, 44 0x89,0xcb,0x30,0x1f,0x8d,0xc6,0x8f,0xaa,0xc8,0x74,0xdc,0xc9,0x5d,0x5c,0x31,0xa4, 45 0x70,0x88,0x61,0x2c,0x9f,0x0d,0x2b,0x87,0x50,0x82,0x54,0x64,0x26,0x7d,0x03,0x40, 46 0x34,0x4b,0x1c,0x73,0xd1,0xc4,0xfd,0x3b,0xcc,0xfb,0x7f,0xab,0xe6,0x3e,0x5b,0xa5, 47 0xad,0x04,0x23,0x9c,0x14,0x51,0x22,0xf0,0x29,0x79,0x71,0x7e,0xff,0x8c,0x0e,0xe2, 48 0x0c,0xef,0xbc,0x72,0x75,0x6f,0x37,0xa1,0xec,0xd3,0x8e,0x62,0x8b,0x86,0x10,0xe8, 49 0x08,0x77,0x11,0xbe,0x92,0x4f,0x24,0xc5,0x32,0x36,0x9d,0xcf,0xf3,0xa6,0xbb,0xac, 50 0x5e,0x6c,0xa9,0x13,0x57,0x25,0xb5,0xe3,0xbd,0xa8,0x3a,0x01,0x05,0x59,0x2a,0x46 51 }; 52 53 /* simple x + 1 (mod 10) in one step. */ 54 static const int keystep[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 }; 55 56 /* simple x - 1 (mod 10) in one step */ 57 static const int ikeystep[] = { 9, 0, 1, 2, 3, 4, 5, 6, 7, 8 }; 58 59 /** 60 Initialize the Skipjack block cipher 61 @param key The symmetric key you wish to pass 62 @param keylen The key length in bytes 63 @param num_rounds The number of rounds desired (0 for default) 64 @param skey The key in as scheduled by this function. 65 @return CRYPT_OK if successful 66 */ 67 int skipjack_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey) 68 { 69 int x; 70 71 LTC_ARGCHK(key != NULL); 72 LTC_ARGCHK(skey != NULL); 73 74 if (keylen != 10) { 75 return CRYPT_INVALID_KEYSIZE; 76 } 77 78 if (num_rounds != 32 && num_rounds != 0) { 79 return CRYPT_INVALID_ROUNDS; 80 } 81 82 /* make sure the key is in range for platforms where CHAR_BIT != 8 */ 83 for (x = 0; x < 10; x++) { 84 skey->skipjack.key[x] = key[x] & 255; 85 } 86 87 return CRYPT_OK; 88 } 89 90 #define RULE_A \ 91 tmp = g_func(w1, &kp, skey->skipjack.key); \ 92 w1 = tmp ^ w4 ^ x; \ 93 w4 = w3; w3 = w2; \ 94 w2 = tmp; 95 96 #define RULE_B \ 97 tmp = g_func(w1, &kp, skey->skipjack.key); \ 98 tmp1 = w4; w4 = w3; \ 99 w3 = w1 ^ w2 ^ x; \ 100 w1 = tmp1; w2 = tmp; 101 102 #define RULE_A1 \ 103 tmp = w1 ^ w2 ^ x; \ 104 w1 = ig_func(w2, &kp, skey->skipjack.key); \ 105 w2 = w3; w3 = w4; w4 = tmp; 106 107 #define RULE_B1 \ 108 tmp = ig_func(w2, &kp, skey->skipjack.key); \ 109 w2 = tmp ^ w3 ^ x; \ 110 w3 = w4; w4 = w1; w1 = tmp; 111 112 static unsigned g_func(unsigned w, int *kp, unsigned char *key) 113 { 114 unsigned char g1,g2; 115 116 g1 = (w >> 8) & 255; g2 = w & 255; 117 g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp]; 118 g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp]; 119 g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp]; 120 g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp]; 121 return ((unsigned)g1<<8)|(unsigned)g2; 122 } 123 124 static unsigned ig_func(unsigned w, int *kp, unsigned char *key) 125 { 126 unsigned char g1,g2; 127 128 g1 = (w >> 8) & 255; g2 = w & 255; 129 *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]]; 130 *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]]; 131 *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]]; 132 *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]]; 133 return ((unsigned)g1<<8)|(unsigned)g2; 134 } 135 136 /** 137 Encrypts a block of text with Skipjack 138 @param pt The input plaintext (8 bytes) 139 @param ct The output ciphertext (8 bytes) 140 @param skey The key as scheduled 141 @return CRYPT_OK if successful 142 */ 143 #ifdef LTC_CLEAN_STACK 144 static int _skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey) 145 #else 146 int skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey) 147 #endif 148 { 149 unsigned w1,w2,w3,w4,tmp,tmp1; 150 int x, kp; 151 152 LTC_ARGCHK(pt != NULL); 153 LTC_ARGCHK(ct != NULL); 154 LTC_ARGCHK(skey != NULL); 155 156 /* load block */ 157 w1 = ((unsigned)pt[0]<<8)|pt[1]; 158 w2 = ((unsigned)pt[2]<<8)|pt[3]; 159 w3 = ((unsigned)pt[4]<<8)|pt[5]; 160 w4 = ((unsigned)pt[6]<<8)|pt[7]; 161 162 /* 8 rounds of RULE A */ 163 for (x = 1, kp = 0; x < 9; x++) { 164 RULE_A; 165 } 166 167 /* 8 rounds of RULE B */ 168 for (; x < 17; x++) { 169 RULE_B; 170 } 171 172 /* 8 rounds of RULE A */ 173 for (; x < 25; x++) { 174 RULE_A; 175 } 176 177 /* 8 rounds of RULE B */ 178 for (; x < 33; x++) { 179 RULE_B; 180 } 181 182 /* store block */ 183 ct[0] = (w1>>8)&255; ct[1] = w1&255; 184 ct[2] = (w2>>8)&255; ct[3] = w2&255; 185 ct[4] = (w3>>8)&255; ct[5] = w3&255; 186 ct[6] = (w4>>8)&255; ct[7] = w4&255; 187 188 return CRYPT_OK; 189 } 190 191 #ifdef LTC_CLEAN_STACK 192 int skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey) 193 { 194 int err = _skipjack_ecb_encrypt(pt, ct, skey); 195 burn_stack(sizeof(unsigned) * 8 + sizeof(int) * 2); 196 return err; 197 } 198 #endif 199 200 /** 201 Decrypts a block of text with Skipjack 202 @param ct The input ciphertext (8 bytes) 203 @param pt The output plaintext (8 bytes) 204 @param skey The key as scheduled 205 @return CRYPT_OK if successful 206 */ 207 #ifdef LTC_CLEAN_STACK 208 static int _skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey) 209 #else 210 int skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey) 211 #endif 212 { 213 unsigned w1,w2,w3,w4,tmp; 214 int x, kp; 215 216 LTC_ARGCHK(pt != NULL); 217 LTC_ARGCHK(ct != NULL); 218 LTC_ARGCHK(skey != NULL); 219 220 /* load block */ 221 w1 = ((unsigned)ct[0]<<8)|ct[1]; 222 w2 = ((unsigned)ct[2]<<8)|ct[3]; 223 w3 = ((unsigned)ct[4]<<8)|ct[5]; 224 w4 = ((unsigned)ct[6]<<8)|ct[7]; 225 226 /* 8 rounds of RULE B^-1 227 228 Note the value "kp = 8" comes from "kp = (32 * 4) mod 10" where 32*4 is 128 which mod 10 is 8 229 */ 230 for (x = 32, kp = 8; x > 24; x--) { 231 RULE_B1; 232 } 233 234 /* 8 rounds of RULE A^-1 */ 235 for (; x > 16; x--) { 236 RULE_A1; 237 } 238 239 240 /* 8 rounds of RULE B^-1 */ 241 for (; x > 8; x--) { 242 RULE_B1; 243 } 244 245 /* 8 rounds of RULE A^-1 */ 246 for (; x > 0; x--) { 247 RULE_A1; 248 } 249 250 /* store block */ 251 pt[0] = (w1>>8)&255; pt[1] = w1&255; 252 pt[2] = (w2>>8)&255; pt[3] = w2&255; 253 pt[4] = (w3>>8)&255; pt[5] = w3&255; 254 pt[6] = (w4>>8)&255; pt[7] = w4&255; 255 256 return CRYPT_OK; 257 } 258 259 #ifdef LTC_CLEAN_STACK 260 int skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey) 261 { 262 int err = _skipjack_ecb_decrypt(ct, pt, skey); 263 burn_stack(sizeof(unsigned) * 7 + sizeof(int) * 2); 264 return err; 265 } 266 #endif 267 268 /** 269 Performs a self-test of the Skipjack block cipher 270 @return CRYPT_OK if functional, CRYPT_NOP if self-test has been disabled 271 */ 272 int skipjack_test(void) 273 { 274 #ifndef LTC_TEST 275 return CRYPT_NOP; 276 #else 277 static const struct { 278 unsigned char key[10], pt[8], ct[8]; 279 } tests[] = { 280 { 281 { 0x00, 0x99, 0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11 }, 282 { 0x33, 0x22, 0x11, 0x00, 0xdd, 0xcc, 0xbb, 0xaa }, 283 { 0x25, 0x87, 0xca, 0xe2, 0x7a, 0x12, 0xd3, 0x00 } 284 } 285 }; 286 unsigned char buf[2][8]; 287 int x, y, err; 288 symmetric_key key; 289 290 for (x = 0; x < (int)(sizeof(tests) / sizeof(tests[0])); x++) { 291 /* setup key */ 292 if ((err = skipjack_setup(tests[x].key, 10, 0, &key)) != CRYPT_OK) { 293 return err; 294 } 295 296 /* encrypt and decrypt */ 297 skipjack_ecb_encrypt(tests[x].pt, buf[0], &key); 298 skipjack_ecb_decrypt(buf[0], buf[1], &key); 299 300 /* compare */ 301 if (XMEMCMP(buf[0], tests[x].ct, 8) != 0 || XMEMCMP(buf[1], tests[x].pt, 8) != 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 } 322 323 /** 324 Gets suitable key size 325 @param keysize [in/out] The length of the recommended key (in bytes). This function will store the suitable size back in this variable. 326 @return CRYPT_OK if the input key size is acceptable. 327 */ 328 int skipjack_keysize(int *keysize) 329 { 330 LTC_ARGCHK(keysize != NULL); 331 if (*keysize < 10) { 332 return CRYPT_INVALID_KEYSIZE; 333 } else if (*keysize > 10) { 334 *keysize = 10; 335 } 336 return CRYPT_OK; 337 } 338 339 #endif 340 341 /* $Source: /cvs/libtom/libtomcrypt/src/ciphers/skipjack.c,v $ */ 342 /* $Revision: 1.12 $ */ 343 /* $Date: 2006/11/08 23:01:06 $ */ 344
