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 */
skipjack_setup(const unsigned char * key,int keylen,int num_rounds,symmetric_key * skey)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
g_func(unsigned w,int * kp,const unsigned char * key)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
ig_func(unsigned w,int * kp,const unsigned char * key)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
_skipjack_ecb_encrypt(const unsigned char * pt,unsigned char * ct,const symmetric_key * skey)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
skipjack_ecb_encrypt(const unsigned char * pt,unsigned char * ct,const symmetric_key * skey)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
_skipjack_ecb_decrypt(const unsigned char * ct,unsigned char * pt,const symmetric_key * skey)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
skipjack_ecb_decrypt(const unsigned char * ct,unsigned char * pt,const symmetric_key * skey)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 */
skipjack_test(void)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 */
skipjack_done(symmetric_key * skey)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 */
skipjack_keysize(int * keysize)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