DES
The Data Encryption Standard (DES) is an symmetric-key algorithm for the encryption of electronic data. DES works by using the same key to encrypt and decrypt a message, so both the sender and the receiver must know and use the same private key.
/*****Please include following header files*****/
// stdint.h
/***********************************************/
#define ENCRYPT 1
#define DECRYPT 0
#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))
#define SBOXBIT(a) (((a) & 0x20) | (((a) & 0x1f) >> 1) | (((a) & 0x01) << 4))
uint8_t 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
};
uint8_t 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
};
uint8_t 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
};
uint8_t 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
};
uint8_t 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
};
uint8_t 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
};
uint8_t 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
};
uint8_t 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
};
void KeySchedule(uint8_t key[], uint8_t schedule[][6], uint32_t mode)
{
uint32_t i, j, toGen, C, D,
key_rnd_shift[16] = { 1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1 },
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 },
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 },
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 };
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);
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;
if (mode == DECRYPT)
toGen = 15 - i;
else
toGen = i;
for (j = 0; j < 6; ++j)
schedule[toGen][j] = 0;
for (j = 0; j < 24; ++j)
schedule[toGen][j / 8] |= BITNUMINTR(C, key_compression[j], 7 - (j % 8));
for (; j < 48; ++j)
schedule[toGen][j / 8] |= BITNUMINTR(D, key_compression[j] - 28, 7 - (j % 8));
}
}
void IP(uint32_t state[], uint8_t 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(uint32_t state[], uint8_t 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);
}
uint32_t F(uint32_t state, uint8_t key[])
{
uint8_t lrgstate[6], i;
uint32_t t1, t2;
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;
lrgstate[0] ^= key[0];
lrgstate[1] ^= key[1];
lrgstate[2] ^= key[2];
lrgstate[3] ^= key[3];
lrgstate[4] ^= key[4];
lrgstate[5] ^= key[5];
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)];
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(state);
}
void Crypt(uint8_t in[], uint8_t out[], uint8_t key[][6])
{
uint32_t 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;
}
state[0] = F(state[1], key[15]) ^ state[0];
InvIP(state, out);
}
Example
/***************Helper Functions***************/
void PrintText(uint8_t hash[])
{
for (int i = 0; i < 8; ++i)
printf("%02x ", hash[i]);
printf("\n");
}
/**********************************************/
/***************Example Code***************/
uint8_t text[8] = { 0x01,0x23,0x45,0x67,0x89,0xAB,0xCD,0xE7 };
uint8_t key[8] = { 0x01,0x23,0x45,0x67,0x89,0xAB,0xCD,0xEF };
uint8_t out[8];
uint8_t schedule[16][6];
KeySchedule(key, schedule, ENCRYPT);
Crypt(text, out, schedule);
printf("Encrypt Output: ");
PrintText(out);
KeySchedule(key, schedule, DECRYPT);
Crypt(out, text, schedule);
printf("Decrypt Output: ");
PrintText(text);
/******************************************/
Output
Encrypt Output: c9 57 44 25 6a 5e d3 1d
Decrypt Output: 01 23 45 67 89 ab cd e7