Data Encryption Standard: Difference between revisions

=={{header|C}}==

{{trans|D}}

<lang c>#include <stdio.h>

#include <stdlib.h>

#include <string.h>

typedef unsigned char ubyte;

#define KEY_LEN 8

typedef ubyte key_t[KEY_LEN];

const static ubyte PC1[] = {

57, 49, 41, 33, 25, 17, 9,

1, 58, 50, 42, 34, 26, 18,

10, 2, 59, 51, 43, 35, 27,

19, 11, 3, 60, 52, 44, 36,

63, 55, 47, 39, 31, 23, 15,

7, 62, 54, 46, 38, 30, 22,

14, 6, 61, 53, 45, 37, 29,

21, 13, 5, 28, 20, 12, 4

};

const static ubyte PC2[] = {

14, 17, 11, 24, 1, 5,

3, 28, 15, 6, 21, 10,

23, 19, 12, 4, 26, 8,

16, 7, 27, 20, 13, 2,

41, 52, 31, 37, 47, 55,

30, 40, 51, 45, 33, 48,

44, 49, 39, 56, 34, 53,

46, 42, 50, 36, 29, 32

};

const static ubyte IP[] = {

58, 50, 42, 34, 26, 18, 10, 2,

60, 52, 44, 36, 28, 20, 12, 4,

62, 54, 46, 38, 30, 22, 14, 6,

64, 56, 48, 40, 32, 24, 16, 8,

57, 49, 41, 33, 25, 17, 9, 1,

59, 51, 43, 35, 27, 19, 11, 3,

61, 53, 45, 37, 29, 21, 13, 5,

63, 55, 47, 39, 31, 23, 15, 7

};

const static ubyte E[] = {

32, 1, 2, 3, 4, 5,

4, 5, 6, 7, 8, 9,

8, 9, 10, 11, 12, 13,

12, 13, 14, 15, 16, 17,

16, 17, 18, 19, 20, 21,

20, 21, 22, 23, 24, 25,

24, 25, 26, 27, 28, 29,

28, 29, 30, 31, 32, 1

};

const static ubyte S[][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

},

{

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

},

{

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

},

{

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

},

{

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

},

{

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

},

{

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

},

{

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

}

};

const static ubyte P[] = {

16, 7, 20, 21,

29, 12, 28, 17,

1, 15, 23, 26,

5, 18, 31, 10,

2, 8, 24, 14,

32, 27, 3, 9,

19, 13, 30, 6,

22, 11, 4, 25

};

const static ubyte IP2[] = {

40, 8, 48, 16, 56, 24, 64, 32,

39, 7, 47, 15, 55, 23, 63, 31,

38, 6, 46, 14, 54, 22, 62, 30,

37, 5, 45, 13, 53, 21, 61, 29,

36, 4, 44, 12, 52, 20, 60, 28,

35, 3, 43, 11, 51, 19, 59, 27,

34, 2, 42, 10, 50, 18, 58, 26,

33, 1, 41, 9, 49, 17, 57, 25

};

const static ubyte SHIFTS[] = {

1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1

};

typedef struct {

ubyte *data;

int len;

} String;

/*

* Transform a single nibble into a hex character

*

* in: a value < 0x10

*

* returns: the character that represents the nibble

*/

static char toHex(ubyte in) {

if (0x00 <= in && in < 0x0A) {

return '0' + in;

}

if (0x0A <= in && in <= 0x0F) {

return 'A' + in - 0x0A;

}

return 0;

}

/*

* Convert an array of bytes into a string

*

* ptr: the array of bytes

* len: the number of bytes

* out: a buffer allocated by the caller with enough space for 2*len+1 characters

*/

static void printBytes(const ubyte *ptr, int len, char *out) {

while (len-- > 0) {

*out++ = toHex(*ptr >> 4);

*out++ = toHex(*ptr & 0x0F);

ptr++;

}

*out = 0;

}

/*

* Gets the value of a bit in an array of bytes

*

* src: the array of bytes to index

* index: the desired bit to test the value of

*

* returns: the bit at the specified position in the array

*/

static int peekBit(const ubyte *src, int index) {

int cell = index / 8;

int bit = 7 - index % 8;

return (src[cell] & (1 << bit)) != 0;

}

/*

* Sets the value of a bit in an array of bytes

*

* dst: the array of bits to set a bit in

* index: the position of the bit to set

* value: the value for the bit to set

*/

static void pokeBit(ubyte *dst, int index, int value) {

int cell = index / 8;

int bit = 7 - index % 8;

if (value == 0) {

dst[cell] &= ~(1 << bit);

} else {

dst[cell] |= (1 << bit);

}

}

/*

* Transforms one array of bytes by shifting the bits the specified number of positions

*

* src: the array to shift bits from

* len: the length of the src array

* times: the number of positions that the bits should be shifted

* dst: a bytes array allocated by the caller to store the shifted values

*/

static void shiftLeft(const ubyte *src, int len, int times, ubyte *dst) {

int i, t;

for (i = 0; i <= len; ++i) {

pokeBit(dst, i, peekBit(src, i));

}

for (t = 1; t <= times; ++t) {

int temp = peekBit(dst, 0);

for (i = 1; i <= len; ++i) {

pokeBit(dst, i - 1, peekBit(dst, i));

}

pokeBit(dst, len - 1, temp);

}

}

/*

* Calculates the sub keys to be used in processing the messages

*

* key: the array of bytes representing the key

* ks: the subkeys that have been allocated by the caller

*/

typedef ubyte subkey_t[17][6]; /* 17 sets of 48 bits */

static void getSubKeys(const key_t key, subkey_t ks) {

ubyte c[17][7]; /* 56 bits */

ubyte d[17][4]; /* 28 bits */

ubyte kp[7];

int i, j;

/* intialize */

memset(c, 0, sizeof(c));

memset(d, 0, sizeof(d));

memset(ks, 0, sizeof(subkey_t));

/* permute 'key' using table PC1 */

for (i = 0; i < 56; ++i) {

pokeBit(kp, i, peekBit(key, PC1[i] - 1));

}

/* split 'kp' in half and process the resulting series of 'c' and 'd' */

for (i = 0; i < 28; ++i) {

pokeBit(c[0], i, peekBit(kp, i));

pokeBit(d[0], i, peekBit(kp, i + 28));

}

/* shift the components of c and d */

for (i = 1; i < 17; ++i) {

shiftLeft(c[i - 1], 28, SHIFTS[i - 1], c[i]);

shiftLeft(d[i - 1], 28, SHIFTS[i - 1], d[i]);

}

/* merge 'd' into 'c' */

for (i = 1; i < 17; ++i) {

for (j = 28; j < 56; ++j) {

pokeBit(c[i], j, peekBit(d[i], j - 28));

}

}

/* form the sub-keys and store them in 'ks'

* permute 'c' using table PC2 */

for (i = 1; i < 17; ++i) {

for (j = 0; j < 48; ++j) {

pokeBit(ks[i], j, peekBit(c[i], PC2[j] - 1));

}

}

}

/*

* Function used in processing the messages

*

* r: an array of bytes to be processed

* ks: one of the subkeys to be used for processing

* sp: output from the processing

*/

static void f(ubyte *r, ubyte *ks, ubyte *sp) {

ubyte er[6]; /* 48 bits */

ubyte sr[4]; /* 32 bits */

int i;

/* initialize */

memset(er, 0, sizeof(er));

memset(sr, 0, sizeof(sr));

/* permute 'r' using table E */

for (i = 0; i < 48; ++i) {

pokeBit(er, i, peekBit(r, E[i] - 1));

}

/* xor 'er' with 'ks' and store back into 'er' */

for (i = 0; i < 6; ++i) {

er[i] ^= ks[i];

}

/* process 'er' six bits at a time and store resulting four bits in 'sr' */

for (i = 0; i < 8; ++i) {

int j = i * 6;

int b[6];

int k, row, col, m, n;

for (k = 0; k < 6; ++k) {

b[k] = peekBit(er, j + k) != 0 ? 1 : 0;

}

row = 2 * b[0] + b[5];

col = 8 * b[1] + 4 * b[2] + 2 * b[3] + b[4];

m = S[i][row * 16 + col]; /* apply table s */

n = 1;

while (m > 0) {

int p = m % 2;

pokeBit(sr, (i + 1) * 4 - n, p == 1);

m /= 2;

n++;

}

}

/* permute sr using table P */

for (i = 0; i < 32; ++i) {

pokeBit(sp, i, peekBit(sr, P[i] - 1));

}

}

/*

* Processing of block of the message

*

* message: an 8 byte block from the message

* ks: the subkeys to use in processing

* ep: space for an encoded 8 byte block allocated by the caller

*/

static void processMessage(const ubyte *message, subkey_t ks, ubyte *ep) {

ubyte left[17][4]; /* 32 bits */

ubyte right[17][4]; /* 32 bits */

ubyte mp[8]; /* 64 bits */

ubyte e[8]; /* 64 bits */

int i, j;

/* permute 'message' using table IP */

for (i = 0; i < 64; ++i) {

pokeBit(mp, i, peekBit(message, IP[i] - 1));

}

/* split 'mp' in half and process the resulting series of 'l' and 'r */

for (i = 0; i < 32; ++i) {

pokeBit(left[0], i, peekBit(mp, i));

pokeBit(right[0], i, peekBit(mp, i + 32));

}

for (i = 1; i < 17; ++i) {

ubyte fs[4]; /* 32 bits */

memcpy(left[i], right[i - 1], 4);

f(right[i - 1], ks[i], fs);

for (j = 0; j < 4; ++j) {

left[i - 1][j] ^= fs[j];

}

memcpy(right[i], left[i - 1], 4);

}

/* amalgamate r[16] and l[16] (in that order) into 'e' */

for (i = 0; i < 32; ++i) {

pokeBit(e, i, peekBit(right[16], i));

}

for (i = 32; i < 64; ++i) {

pokeBit(e, i, peekBit(left[16], i - 32));

}

/* permute 'e' using table IP2 ad return result as a hex string */

for (i = 0; i < 64; ++i) {

pokeBit(ep, i, peekBit(e, IP2[i] - 1));

}

}

/*

* Encrypts a message using DES

*

* key: the key to use to encrypt the message

* message: the message to be encrypted

* len: the length of the message

*

* returns: a paring of dynamically allocated memory for the encoded message,

* and the length of the encoded message.

* the caller will need to free the memory after use.

*/

String encrypt(const key_t key, const ubyte *message, int len) {

String result = { 0, 0 };

subkey_t ks;

ubyte padByte;

int i;

getSubKeys(key, ks);

padByte = 8 - len % 8;

result.len = len + padByte;

result.data = (ubyte*)malloc(result.len);

memcpy(result.data, message, len);

memset(&result.data[len], padByte, padByte);

for (i = 0; i < result.len; i += 8) {

processMessage(&result.data[i], ks, &result.data[i]);

}

return result;

}

/*

* Decrypts a message using DES

*

* key: the key to use to decrypt the message

* message: the message to be decrypted

* len: the length of the message

*

* returns: a paring of dynamically allocated memory for the decoded message,

* and the length of the decoded message.

* the caller will need to free the memory after use.

*/

String decrypt(const key_t key, const ubyte *message, int len) {

String result = { 0, 0 };

subkey_t ks;

int i, j;

ubyte padByte;

getSubKeys(key, ks);

/* reverse the subkeys */

for (i = 1; i < 9; ++i) {

for (j = 0; j < 6; ++j) {

ubyte temp = ks[i][j];

ks[i][j] = ks[17 - i][j];

ks[17 - i][j] = temp;

}

}

result.data = (ubyte*)malloc(len);

memcpy(result.data, message, len);

result.len = len;

for (i = 0; i < result.len; i += 8) {

processMessage(&result.data[i], ks, &result.data[i]);

}

padByte = result.data[len - 1];

result.len -= padByte;

return result;

}

/*

* Convienience method for showing the round trip processing of a message

*/

void driver(const key_t key, const ubyte *message, int len) {

String encoded, decoded;

char buffer[128];

printBytes(key, KEY_LEN, buffer);

printf("Key : %s\n", buffer);

printBytes(message, len, buffer);

printf("Message : %s\n", buffer);

encoded = encrypt(key, message, len);

printBytes(encoded.data, encoded.len, buffer);

printf("Encoded : %s\n", buffer);

decoded = decrypt(key, encoded.data, encoded.len);

printBytes(decoded.data, decoded.len, buffer);

printf("Decoded : %s\n\n", buffer);

/* release allocated memory */

if (encoded.len > 0) {

free(encoded.data);

encoded.data = 0;

}

if (decoded.len > 0) {

free(decoded.data);

decoded.data = 0;

}

}

int main() {

const key_t keys[] = {

{0x13, 0x34, 0x57, 0x79, 0x9B, 0xBC, 0xDF, 0xF1},

{0x0E, 0x32, 0x92, 0x32, 0xEA, 0x6D, 0x0D, 0x73},

{0x0E, 0x32, 0x92, 0x32, 0xEA, 0x6D, 0x0D, 0x73}

};

const ubyte message1[] = { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF };

const ubyte message2[] = { 0x87, 0x87, 0x87, 0x87, 0x87, 0x87, 0x87, 0x87 };

const ubyte message3[] = { 0x59, 0x6F, 0x75, 0x72, 0x20, 0x6C, 0x69, 0x70, 0x73, 0x20, 0x61, 0x72, 0x65, 0x20, 0x73, 0x6D, 0x6F, 0x6F, 0x74, 0x68, 0x65, 0x72, 0x20, 0x74, 0x68, 0x61, 0x6E, 0x20, 0x76, 0x61, 0x73, 0x65, 0x6C, 0x69, 0x6E, 0x65, 0x0D, 0x0A };

int len;

len = sizeof(message1) / sizeof(ubyte);

driver(keys[0], message1, len);

len = sizeof(message2) / sizeof(ubyte);

driver(keys[1], message2, len);

len = sizeof(message3) / sizeof(ubyte);

driver(keys[2], message3, len);

system("pause"); // translation of d

return 0;

}</lang>

{{out}}

<pre>Key : 133457799BBCDFF1

Message : 0123456789ABCDEF

Encoded : 85E813540F0AB405FDF2E174492922F8

Decoded : 0123456789ABCDEF

Key : 0E329232EA6D0D73

Message : 8787878787878787

Encoded : 0000000000000000A913F4CB0BD30F97

Decoded : 8787878787878787

Key : 0E329232EA6D0D73

Message : 596F7572206C6970732061726520736D6F6F74686572207468616E20766173656C696E650D0A

Encoded : C0999FDDE378D7ED727DA00BCA5A84EE47F269A4D6438190D9D52F78F53584997F922CCB5B068D99

Decoded : 596F7572206C6970732061726520736D6F6F74686572207468616E20766173656C696E650D0A</pre>