/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org *//* Skipjack Implementation by Tom St Denis */#include "mycrypt.h"#ifdef SKIPJACKconst struct _cipher_descriptor skipjack_desc ={    "skipjack",    17,    10, 10, 8, 32,    &skipjack_setup,    &skipjack_ecb_encrypt,    &skipjack_ecb_decrypt,    &skipjack_test,    &skipjack_keysize};static const unsigned char sbox[256] = {   0xa3,0xd7,0x09,0x83,0xf8,0x48,0xf6,0xf4,0xb3,0x21,0x15,0x78,0x99,0xb1,0xaf,0xf9,   0xe7,0x2d,0x4d,0x8a,0xce,0x4c,0xca,0x2e,0x52,0x95,0xd9,0x1e,0x4e,0x38,0x44,0x28,   0x0a,0xdf,0x02,0xa0,0x17,0xf1,0x60,0x68,0x12,0xb7,0x7a,0xc3,0xe9,0xfa,0x3d,0x53,   0x96,0x84,0x6b,0xba,0xf2,0x63,0x9a,0x19,0x7c,0xae,0xe5,0xf5,0xf7,0x16,0x6a,0xa2,   0x39,0xb6,0x7b,0x0f,0xc1,0x93,0x81,0x1b,0xee,0xb4,0x1a,0xea,0xd0,0x91,0x2f,0xb8,   0x55,0xb9,0xda,0x85,0x3f,0x41,0xbf,0xe0,0x5a,0x58,0x80,0x5f,0x66,0x0b,0xd8,0x90,   0x35,0xd5,0xc0,0xa7,0x33,0x06,0x65,0x69,0x45,0x00,0x94,0x56,0x6d,0x98,0x9b,0x76,   0x97,0xfc,0xb2,0xc2,0xb0,0xfe,0xdb,0x20,0xe1,0xeb,0xd6,0xe4,0xdd,0x47,0x4a,0x1d,   0x42,0xed,0x9e,0x6e,0x49,0x3c,0xcd,0x43,0x27,0xd2,0x07,0xd4,0xde,0xc7,0x67,0x18,   0x89,0xcb,0x30,0x1f,0x8d,0xc6,0x8f,0xaa,0xc8,0x74,0xdc,0xc9,0x5d,0x5c,0x31,0xa4,   0x70,0x88,0x61,0x2c,0x9f,0x0d,0x2b,0x87,0x50,0x82,0x54,0x64,0x26,0x7d,0x03,0x40,   0x34,0x4b,0x1c,0x73,0xd1,0xc4,0xfd,0x3b,0xcc,0xfb,0x7f,0xab,0xe6,0x3e,0x5b,0xa5,   0xad,0x04,0x23,0x9c,0x14,0x51,0x22,0xf0,0x29,0x79,0x71,0x7e,0xff,0x8c,0x0e,0xe2,   0x0c,0xef,0xbc,0x72,0x75,0x6f,0x37,0xa1,0xec,0xd3,0x8e,0x62,0x8b,0x86,0x10,0xe8,   0x08,0x77,0x11,0xbe,0x92,0x4f,0x24,0xc5,0x32,0x36,0x9d,0xcf,0xf3,0xa6,0xbb,0xac,   0x5e,0x6c,0xa9,0x13,0x57,0x25,0xb5,0xe3,0xbd,0xa8,0x3a,0x01,0x05,0x59,0x2a,0x46};/* simple x + 1 (mod 10) in one step. */static const int keystep[] =  { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };/* simple x - 1 (mod 10) in one step */static const int ikeystep[] = { 9, 0, 1, 2, 3, 4, 5, 6, 7, 8 };int skipjack_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey){   int x;   _ARGCHK(key  != NULL);   _ARGCHK(skey != NULL);   if (keylen != 10) {      return CRYPT_INVALID_KEYSIZE;   }   if (num_rounds != 32 && num_rounds != 0) {       return CRYPT_INVALID_ROUNDS;   }   /* make sure the key is in range for platforms where CHAR_BIT != 8 */   for (x = 0; x < 10; x++) {       skey->skipjack.key[x] = key[x] & 255;   }   return CRYPT_OK;}#define RULE_A \   tmp = g_func(w1, &kp, key->skipjack.key);      \   w1  = tmp ^ w4 ^ x;                            \   w4  = w3; w3 = w2;                             \   w2  = tmp;#define RULE_B \   tmp  = g_func(w1, &kp, key->skipjack.key);     \   tmp1 = w4; w4  = w3;                           \   w3   = w1 ^ w2 ^ x;                            \   w1   = tmp1; w2 = tmp;#define RULE_A1 \   tmp = w1 ^ w2 ^ x;                             \   w1  = ig_func(w2, &kp, key->skipjack.key);     \   w2  = w3; w3 = w4; w4 = tmp;#define RULE_B1 \   tmp = ig_func(w2, &kp, key->skipjack.key);     \   w2  = tmp ^ w3 ^ x;                            \   w3  = w4; w4 = w1; w1 = tmp;static unsigned g_func(unsigned w, int *kp, unsigned char *key){   unsigned char g1,g2;   g1 = (w >> 8) & 255; g2 = w & 255;   g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp];   g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp];   g1 ^= sbox[g2^key[*kp]]; *kp = keystep[*kp];   g2 ^= sbox[g1^key[*kp]]; *kp = keystep[*kp];   return ((unsigned)g1<<8)|(unsigned)g2;}static unsigned ig_func(unsigned w, int *kp, unsigned char *key){   unsigned char g1,g2;   g1 = (w >> 8) & 255; g2 = w & 255;   *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]];   *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]];   *kp = ikeystep[*kp]; g2 ^= sbox[g1^key[*kp]];   *kp = ikeystep[*kp]; g1 ^= sbox[g2^key[*kp]];   return ((unsigned)g1<<8)|(unsigned)g2;}#ifdef CLEAN_STACKstatic void _skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *key)#elsevoid skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *key)#endif{   unsigned w1,w2,w3,w4,tmp,tmp1;   int x, kp;   _ARGCHK(pt != NULL);   _ARGCHK(ct != NULL);   _ARGCHK(key != NULL);   /* load block */   w1 = ((unsigned)pt[0]<<8)|pt[1];   w2 = ((unsigned)pt[2]<<8)|pt[3];   w3 = ((unsigned)pt[4]<<8)|pt[5];   w4 = ((unsigned)pt[6]<<8)|pt[7];   /* 8 rounds of RULE A */   for (x = 1, kp = 0; x < 9; x++) {       RULE_A;   }   /* 8 rounds of RULE B */   for (; x < 17; x++) {       RULE_B;   }   /* 8 rounds of RULE A */   for (; x < 25; x++) {       RULE_A;   }   /* 8 rounds of RULE B */   for (; x < 33; x++) {       RULE_B;   }   /* store block */   ct[0] = (w1>>8)&255; ct[1] = w1&255;   ct[2] = (w2>>8)&255; ct[3] = w2&255;   ct[4] = (w3>>8)&255; ct[5] = w3&255;   ct[6] = (w4>>8)&255; ct[7] = w4&255;}#ifdef CLEAN_STACKvoid skipjack_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *key){   _skipjack_ecb_encrypt(pt, ct, key);   burn_stack(sizeof(unsigned) * 8 + sizeof(int) * 2);}#endif#ifdef CLEAN_STACKstatic void _skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *key)#elsevoid skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *key)#endif{   unsigned w1,w2,w3,w4,tmp;   int x, kp;   _ARGCHK(pt != NULL);   _ARGCHK(ct != NULL);   _ARGCHK(key != NULL);   /* load block */   w1 = ((unsigned)ct[0]<<8)|ct[1];   w2 = ((unsigned)ct[2]<<8)|ct[3];   w3 = ((unsigned)ct[4]<<8)|ct[5];   w4 = ((unsigned)ct[6]<<8)|ct[7];   /* 8 rounds of RULE B^-1       Note the value "kp = 8" comes from "kp = (32 * 4) mod 10" where 32*4 is 128 which mod 10 is 8    */   for (x = 32, kp = 8; x > 24; x--) {       RULE_B1;   }   /* 8 rounds of RULE A^-1 */   for (; x > 16; x--) {       RULE_A1;   }   /* 8 rounds of RULE B^-1 */   for (; x > 8; x--) {       RULE_B1;   }   /* 8 rounds of RULE A^-1 */   for (; x > 0; x--) {       RULE_A1;   }   /* store block */   pt[0] = (w1>>8)&255; pt[1] = w1&255;   pt[2] = (w2>>8)&255; pt[3] = w2&255;   pt[4] = (w3>>8)&255; pt[5] = w3&255;   pt[6] = (w4>>8)&255; pt[7] = w4&255;}#ifdef CLEAN_STACKvoid skipjack_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *key){   _skipjack_ecb_decrypt(ct, pt, key);   burn_stack(sizeof(unsigned) * 7 + sizeof(int) * 2);}#endifint skipjack_test(void){ #ifndef LTC_TEST    return CRYPT_NOP; #else       static const struct {       unsigned char key[10], pt[8], ct[8];   } tests[] = {   {       { 0x00, 0x99, 0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11 },       { 0x33, 0x22, 0x11, 0x00, 0xdd, 0xcc, 0xbb, 0xaa },       { 0x25, 0x87, 0xca, 0xe2, 0x7a, 0x12, 0xd3, 0x00 }   }   };   unsigned char buf[2][8];   int x, y, err;   symmetric_key key;   for (x = 0; x < (int)(sizeof(tests) / sizeof(tests[0])); x++) {      /* setup key */      if ((err = skipjack_setup(tests[x].key, 10, 0, &key)) != CRYPT_OK) {         return err;      }      /* encrypt and decrypt */      skipjack_ecb_encrypt(tests[x].pt, buf[0], &key);      skipjack_ecb_decrypt(buf[0], buf[1], &key);      /* compare */      if (memcmp(buf[0], tests[x].ct, 8) != 0 || memcmp(buf[1], tests[x].pt, 8) != 0) {         return CRYPT_FAIL_TESTVECTOR;      }      /* now see if we can encrypt all zero bytes 1000 times, decrypt and come back where we started */      for (y = 0; y < 8; y++) buf[0][y] = 0;      for (y = 0; y < 1000; y++) skipjack_ecb_encrypt(buf[0], buf[0], &key);      for (y = 0; y < 1000; y++) skipjack_ecb_decrypt(buf[0], buf[0], &key);      for (y = 0; y < 8; y++) if (buf[0][y] != 0) return CRYPT_FAIL_TESTVECTOR;   }   return CRYPT_OK;  #endif}int skipjack_keysize(int *desired_keysize){   _ARGCHK(desired_keysize != NULL);   if (*desired_keysize < 10) {      return CRYPT_INVALID_KEYSIZE;   } else if (*desired_keysize > 10) {      *desired_keysize = 10;   }   return CRYPT_OK;}#endif