text: /*********************************************************************
  * Filename:   des.c
  * Details:    Implementation of the DES encryption algorithm.
                Modes of operation (such as CBC) are not included.
                The formal NIST algorithm specification can be found here:
                 * http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf
  *********************************************************************/
  
  /*************************** HEADER FILES ***************************/
  #include <stdlib.h>
  #include <memory.h>
  #include "des.h"
  
  /****************************** MACROS ******************************/
  // Obtain bit "b" from the left and shift it "c" places from the right
  #define BITNUM(a, b, c) (((a[(b) / 8] >> (7 - (b % 8))) & 0x01) << (c))
  #define BITNUMINTR(a, b, c) ((((a) >> (31 - (b))) & 0x00000001) << (c))
  #define BITNUMINTL(a, b, c) ((((a) << (b)) & 0x80000000) >> (c))
  
  // This macro converts a 6 bit block with the S-Box row defined as the first and last
  // bits to a 6 bit block with the row defined by the first two bits.
  #define SBOXBIT(a) (((a)&0x20) | (((a)&0x1f) >> 1) | (((a)&0x01) << 4))
  
  /**************************** VARIABLES *****************************/
  static const BYTE sbox1[64] = {
  	14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
  	0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
  	4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
  	15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13};
  static const BYTE sbox2[64] = {
  	15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
  	3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
  	0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
  	13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9};
  static const BYTE sbox3[64] = {
  	10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
  	13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
  	13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
  	1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12};
  static const BYTE sbox4[64] = {
  	7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
  	13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
  	10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
  	3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14};
  static const BYTE sbox5[64] = {
  	2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
  	14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
  	4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
  	11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3};
  static const BYTE sbox6[64] = {
  	12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
  	10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
  	9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
  	4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13};
  static const BYTE sbox7[64] = {
  	4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
  	13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
  	1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
  	6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12};
  static const BYTE sbox8[64] = {
  	13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
  	1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
  	7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
  	2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11};
  
  /*********************** FUNCTION DEFINITIONS ***********************/
  // Initial (Inv)Permutation step
  void IP(WORD state[], const BYTE in[])
  {
  	state[0] = BITNUM(in, 57, 31) | BITNUM(in, 49, 30) | BITNUM(in, 41, 29) | BITNUM(in, 33, 28) |
  			   BITNUM(in, 25, 27) | BITNUM(in, 17, 26) | BITNUM(in, 9, 25) | BITNUM(in, 1, 24) |
  			   BITNUM(in, 59, 23) | BITNUM(in, 51, 22) | BITNUM(in, 43, 21) | BITNUM(in, 35, 20) |
  			   BITNUM(in, 27, 19) | BITNUM(in, 19, 18) | BITNUM(in, 11, 17) | BITNUM(in, 3, 16) |
  			   BITNUM(in, 61, 15) | BITNUM(in, 53, 14) | BITNUM(in, 45, 13) | BITNUM(in, 37, 12) |
  			   BITNUM(in, 29, 11) | BITNUM(in, 21, 10) | BITNUM(in, 13, 9) | BITNUM(in, 5, 8) |
  			   BITNUM(in, 63, 7) | BITNUM(in, 55, 6) | BITNUM(in, 47, 5) | BITNUM(in, 39, 4) |
  			   BITNUM(in, 31, 3) | BITNUM(in, 23, 2) | BITNUM(in, 15, 1) | BITNUM(in, 7, 0);
  
  	state[1] = BITNUM(in, 56, 31) | BITNUM(in, 48, 30) | BITNUM(in, 40, 29) | BITNUM(in, 32, 28) |
  			   BITNUM(in, 24, 27) | BITNUM(in, 16, 26) | BITNUM(in, 8, 25) | BITNUM(in, 0, 24) |
  			   BITNUM(in, 58, 23) | BITNUM(in, 50, 22) | BITNUM(in, 42, 21) | BITNUM(in, 34, 20) |
  			   BITNUM(in, 26, 19) | BITNUM(in, 18, 18) | BITNUM(in, 10, 17) | BITNUM(in, 2, 16) |
  			   BITNUM(in, 60, 15) | BITNUM(in, 52, 14) | BITNUM(in, 44, 13) | BITNUM(in, 36, 12) |
  			   BITNUM(in, 28, 11) | BITNUM(in, 20, 10) | BITNUM(in, 12, 9) | BITNUM(in, 4, 8) |
  			   BITNUM(in, 62, 7) | BITNUM(in, 54, 6) | BITNUM(in, 46, 5) | BITNUM(in, 38, 4) |
  			   BITNUM(in, 30, 3) | BITNUM(in, 22, 2) | BITNUM(in, 14, 1) | BITNUM(in, 6, 0);
  }
  
  void InvIP(WORD state[], BYTE in[])
  {
  	in[0] = BITNUMINTR(state[1], 7, 7) | BITNUMINTR(state[0], 7, 6) | BITNUMINTR(state[1], 15, 5) |
  			BITNUMINTR(state[0], 15, 4) | BITNUMINTR(state[1], 23, 3) | BITNUMINTR(state[0], 23, 2) |
  			BITNUMINTR(state[1], 31, 1) | BITNUMINTR(state[0], 31, 0);
  
  	in[1] = BITNUMINTR(state[1], 6, 7) | BITNUMINTR(state[0], 6, 6) | BITNUMINTR(state[1], 14, 5) |
  			BITNUMINTR(state[0], 14, 4) | BITNUMINTR(state[1], 22, 3) | BITNUMINTR(state[0], 22, 2) |
  			BITNUMINTR(state[1], 30, 1) | BITNUMINTR(state[0], 30, 0);
  
  	in[2] = BITNUMINTR(state[1], 5, 7) | BITNUMINTR(state[0], 5, 6) | BITNUMINTR(state[1], 13, 5) |
  			BITNUMINTR(state[0], 13, 4) | BITNUMINTR(state[1], 21, 3) | BITNUMINTR(state[0], 21, 2) |
  			BITNUMINTR(state[1], 29, 1) | BITNUMINTR(state[0], 29, 0);
  
  	in[3] = BITNUMINTR(state[1], 4, 7) | BITNUMINTR(state[0], 4, 6) | BITNUMINTR(state[1], 12, 5) |
  			BITNUMINTR(state[0], 12, 4) | BITNUMINTR(state[1], 20, 3) | BITNUMINTR(state[0], 20, 2) |
  			BITNUMINTR(state[1], 28, 1) | BITNUMINTR(state[0], 28, 0);
  
  	in[4] = BITNUMINTR(state[1], 3, 7) | BITNUMINTR(state[0], 3, 6) | BITNUMINTR(state[1], 11, 5) |
  			BITNUMINTR(state[0], 11, 4) | BITNUMINTR(state[1], 19, 3) | BITNUMINTR(state[0], 19, 2) |
  			BITNUMINTR(state[1], 27, 1) | BITNUMINTR(state[0], 27, 0);
  
  	in[5] = BITNUMINTR(state[1], 2, 7) | BITNUMINTR(state[0], 2, 6) | BITNUMINTR(state[1], 10, 5) |
  			BITNUMINTR(state[0], 10, 4) | BITNUMINTR(state[1], 18, 3) | BITNUMINTR(state[0], 18, 2) |
  			BITNUMINTR(state[1], 26, 1) | BITNUMINTR(state[0], 26, 0);
  
  	in[6] = BITNUMINTR(state[1], 1, 7) | BITNUMINTR(state[0], 1, 6) | BITNUMINTR(state[1], 9, 5) |
  			BITNUMINTR(state[0], 9, 4) | BITNUMINTR(state[1], 17, 3) | BITNUMINTR(state[0], 17, 2) |
  			BITNUMINTR(state[1], 25, 1) | BITNUMINTR(state[0], 25, 0);
  
  	in[7] = BITNUMINTR(state[1], 0, 7) | BITNUMINTR(state[0], 0, 6) | BITNUMINTR(state[1], 8, 5) |
  			BITNUMINTR(state[0], 8, 4) | BITNUMINTR(state[1], 16, 3) | BITNUMINTR(state[0], 16, 2) |
  			BITNUMINTR(state[1], 24, 1) | BITNUMINTR(state[0], 24, 0);
  }
  
  WORD f(WORD state, const BYTE key[])
  {
  	BYTE lrgstate[6]; //,i;
  	WORD t1, t2;
  
  	// Expantion Permutation
  	t1 = BITNUMINTL(state, 31, 0) | ((state & 0xf0000000) >> 1) | BITNUMINTL(state, 4, 5) |
  		 BITNUMINTL(state, 3, 6) | ((state & 0x0f000000) >> 3) | BITNUMINTL(state, 8, 11) |
  		 BITNUMINTL(state, 7, 12) | ((state & 0x00f00000) >> 5) | BITNUMINTL(state, 12, 17) |
  		 BITNUMINTL(state, 11, 18) | ((state & 0x000f0000) >> 7) | BITNUMINTL(state, 16, 23);
  
  	t2 = BITNUMINTL(state, 15, 0) | ((state & 0x0000f000) << 15) | BITNUMINTL(state, 20, 5) |
  		 BITNUMINTL(state, 19, 6) | ((state & 0x00000f00) << 13) | BITNUMINTL(state, 24, 11) |
  		 BITNUMINTL(state, 23, 12) | ((state & 0x000000f0) << 11) | BITNUMINTL(state, 28, 17) |
  		 BITNUMINTL(state, 27, 18) | ((state & 0x0000000f) << 9) | BITNUMINTL(state, 0, 23);
  
  	lrgstate[0] = (t1 >> 24) & 0x000000ff;
  	lrgstate[1] = (t1 >> 16) & 0x000000ff;
  	lrgstate[2] = (t1 >> 8) & 0x000000ff;
  	lrgstate[3] = (t2 >> 24) & 0x000000ff;
  	lrgstate[4] = (t2 >> 16) & 0x000000ff;
  	lrgstate[5] = (t2 >> 8) & 0x000000ff;
  
  	// Key XOR
  	lrgstate[0] ^= key[0];
  	lrgstate[1] ^= key[1];
  	lrgstate[2] ^= key[2];
  	lrgstate[3] ^= key[3];
  	lrgstate[4] ^= key[4];
  	lrgstate[5] ^= key[5];
  
  	// S-Box Permutation
  	state = (sbox1[SBOXBIT(lrgstate[0] >> 2)] << 28) |
  			(sbox2[SBOXBIT(((lrgstate[0] & 0x03) << 4) | (lrgstate[1] >> 4))] << 24) |
  			(sbox3[SBOXBIT(((lrgstate[1] & 0x0f) << 2) | (lrgstate[2] >> 6))] << 20) |
  			(sbox4[SBOXBIT(lrgstate[2] & 0x3f)] << 16) |
  			(sbox5[SBOXBIT(lrgstate[3] >> 2)] << 12) |
  			(sbox6[SBOXBIT(((lrgstate[3] & 0x03) << 4) | (lrgstate[4] >> 4))] << 8) |
  			(sbox7[SBOXBIT(((lrgstate[4] & 0x0f) << 2) | (lrgstate[5] >> 6))] << 4) |
  			sbox8[SBOXBIT(lrgstate[5] & 0x3f)];
  
  	// P-Box Permutation
  	state = BITNUMINTL(state, 15, 0) | BITNUMINTL(state, 6, 1) | BITNUMINTL(state, 19, 2) |
  			BITNUMINTL(state, 20, 3) | BITNUMINTL(state, 28, 4) | BITNUMINTL(state, 11, 5) |
  			BITNUMINTL(state, 27, 6) | BITNUMINTL(state, 16, 7) | BITNUMINTL(state, 0, 8) |
  			BITNUMINTL(state, 14, 9) | BITNUMINTL(state, 22, 10) | BITNUMINTL(state, 25, 11) |
  			BITNUMINTL(state, 4, 12) | BITNUMINTL(state, 17, 13) | BITNUMINTL(state, 30, 14) |
  			BITNUMINTL(state, 9, 15) | BITNUMINTL(state, 1, 16) | BITNUMINTL(state, 7, 17) |
  			BITNUMINTL(state, 23, 18) | BITNUMINTL(state, 13, 19) | BITNUMINTL(state, 31, 20) |
  			BITNUMINTL(state, 26, 21) | BITNUMINTL(state, 2, 22) | BITNUMINTL(state, 8, 23) |
  			BITNUMINTL(state, 18, 24) | BITNUMINTL(state, 12, 25) | BITNUMINTL(state, 29, 26) |
  			BITNUMINTL(state, 5, 27) | BITNUMINTL(state, 21, 28) | BITNUMINTL(state, 10, 29) |
  			BITNUMINTL(state, 3, 30) | BITNUMINTL(state, 24, 31);
  
  	// Return the final state value
  	return (state);
  }
  
  void des_key_setup(const BYTE key[], BYTE schedule[][6], DES_MODE mode)
  {
  	WORD i, j, to_gen, C, D;
  	const WORD key_rnd_shift[16] = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};
  	const WORD key_perm_c[28] = {56, 48, 40, 32, 24, 16, 8, 0, 57, 49, 41, 33, 25, 17,
  								 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35};
  	const WORD key_perm_d[28] = {62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21,
  								 13, 5, 60, 52, 44, 36, 28, 20, 12, 4, 27, 19, 11, 3};
  	const WORD key_compression[48] = {13, 16, 10, 23, 0, 4, 2, 27, 14, 5, 20, 9,
  									  22, 18, 11, 3, 25, 7, 15, 6, 26, 19, 12, 1,
  									  40, 51, 30, 36, 46, 54, 29, 39, 50, 44, 32, 47,
  									  43, 48, 38, 55, 33, 52, 45, 41, 49, 35, 28, 31};
  
  	// Permutated Choice #1 (copy the key in, ignoring parity bits).
  	for (i = 0, j = 31, C = 0; i < 28; ++i, --j)
  		C |= BITNUM(key, key_perm_c[i], j);
  	for (i = 0, j = 31, D = 0; i < 28; ++i, --j)
  		D |= BITNUM(key, key_perm_d[i], j);
  
  	// Generate the 16 subkeys.
  	for (i = 0; i < 16; ++i)
  	{
  		C = ((C << key_rnd_shift[i]) | (C >> (28 - key_rnd_shift[i]))) & 0xfffffff0;
  		D = ((D << key_rnd_shift[i]) | (D >> (28 - key_rnd_shift[i]))) & 0xfffffff0;
  
  		// Decryption subkeys are reverse order of encryption subkeys so
  		// generate them in reverse if the key schedule is for decryption useage.
  		if (mode == DES_DECRYPT)
  			to_gen = 15 - i;
  		else /*(if mode == DES_ENCRYPT)*/
  			to_gen = i;
  		// Initialize the array
  		for (j = 0; j < 6; ++j)
  			schedule[to_gen][j] = 0;
  		for (j = 0; j < 24; ++j)
  			schedule[to_gen][j / 8] |= BITNUMINTR(C, key_compression[j], 7 - (j % 8));
  		for (; j < 48; ++j)
  			schedule[to_gen][j / 8] |= BITNUMINTR(D, key_compression[j] - 28, 7 - (j % 8));
  	}
  }
  
  void des_crypt(const BYTE in[], BYTE out[], const BYTE key[][6])
  {
  	WORD state[2], idx, t;
  
  	IP(state, in);
  
  	for (idx = 0; idx < 15; ++idx)
  	{
  		t = state[1];
  		state[1] = f(state[1], key[idx]) ^ state[0];
  		state[0] = t;
  	}
  	// Perform the final loop manually as it doesn't switch sides
  	state[0] = f(state[1], key[15]) ^ state[0];
  
  	InvIP(state, out);
  }
  
  void three_des_key_setup(const BYTE key[], BYTE schedule[][16][6], DES_MODE mode)
  {
  	if (mode == DES_ENCRYPT)
  	{
  		des_key_setup(&key[0], schedule[0], mode);
  		des_key_setup(&key[8], schedule[1], !mode);
  		des_key_setup(&key[16], schedule[2], mode);
  	}
  	else /*if (mode == DES_DECRYPT*/
  	{
  		des_key_setup(&key[16], schedule[0], mode);
  		des_key_setup(&key[8], schedule[1], !mode);
  		des_key_setup(&key[0], schedule[2], mode);
  	}
  }
  
  void three_des_crypt(const BYTE in[], BYTE out[], const BYTE key[][16][6])
  {
  	des_crypt(in, out, key[0]);
  	des_crypt(out, out, key[1]);
  	des_crypt(out, out, key[2]);
  }