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