Simple C Program For DES Algorithm in Cryptography
Learn how to implement DES algorithm in C programming language. The DES encryption algorithm is an implementation of Fiestel Cipher. There are two different methods enlisted here for DES algorithm implementation in C programming.
What is DES Encryption Algorithm?
The DES algorithm is also sometimes referred to as Data Encryption Algorithm (DEA). The DES encryption algorithm is a symmetric key algorithm for the encryption of data. The block size is of 64 bits.
The DES is an archetypal block cipher which takes a fixed length string of plain-text bits. There’s another improvised version of this algorithm which is Triple DES Algorithm.
The simplified DES (S-DES) is a modified version of the data encryption standard DES algorithm. Another modified version of the DES algorithm is famously known as Triple DES. The key generator method creates 16 48-bit keys.
Note: This implementation of simplified data encryption standard in C programming language is compiled with GNU GCC compiler on Linux Ubuntu 14.04 operating system.
Method 1: C Program To Implement Data Encryption Standard Algorithm
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 | #include "custom_header.h" #include <stdio.h> #include <stdlib.h> int key_shift_sizes[] = {-1, 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1}; int key_permutation[] = { 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 }; int message_permutation[] = { 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 }; int sub_key_permutation[] = { 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 }; int message[] = { 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 }; int array_a1[] = { 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 }; int array_a2[] = { 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 }; int array_a3[] = { 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 }; int array_a4[] = { 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 }; int array_a5[] = { 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 }; int array_a6[] = { 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 }; int array_a7[] = { 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 }; int array_a8[] = { 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 }; int intermediate_permutation[] = { 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 }; int end_permutation[] = { 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 }; void make_keys(unsigned char* key) { int count; for(count = 0; count < 8; count++) { key[count] = rand()%255; } } void binary_digits(char input) { int count; for(count = 0; count < 8; count++) { char shift_byte = 0x01 << (7 - count); if(shift_byte & input) { printf("1"); } else { printf("0"); } } } void display_keys(key_set key_set) { int count; printf("Y: \n"); for(count = 0; count < 8; count++) { printf("%02X : ", key_set.temp[count]); binary_digits(key_set.temp[count]); printf("\n"); } printf("\nX: \n"); for(count = 0; count < 4; count++) { printf("%02X : ", key_set.y[count]); binary_digits(key_set.y[count]); printf("\n"); } printf("\nZ: \n"); for(count = 0; count < 4; count++) { printf("%02X : ", key_set.z[count]); binary_digits(key_set.z[count]); printf("\n"); } printf("\n"); } void key_maker(unsigned char* main_key, key_set* key_sets) { int m, n; int shift_size; unsigned char shift_byte, first_bit, second_bit, third_bit, fourth_bit; for(m = 0; m < 8; m++) { key_sets[0].temp[m] = 0; } for(m = 0; m < 56; m++) { shift_size = key_permutation[m]; shift_byte = 0x80 >> ((shift_size - 1)%8); shift_byte &= main_key[(shift_size - 1)/8]; shift_byte <<= ((shift_size - 1)%8); key_sets[0].temp[m/8] |= (shift_byte >> m%8); } for(m = 0; m < 3; m++) { key_sets[0].y[m] = key_sets[0].temp[m]; } key_sets[0].y[3] = key_sets[0].temp[3] & 0xF0; for(m = 0; m < 3; m++) { key_sets[0].z[m] = (key_sets[0].temp[m + 3] & 0x0F) << 4; key_sets[0].z[m] |= (key_sets[0].temp[m + 4] & 0xF0) >> 4; } key_sets[0].z[3] = (key_sets[0].temp[6] & 0x0F) << 4; for(m = 1; m < 17; m++) { for(n = 0; n < 4; n++) { key_sets[m].y[n] = key_sets[m - 1].y[n]; key_sets[m].z[n] = key_sets[m - 1].z[n]; } shift_size = key_shift_sizes[i]; if(shift_size == 1) { shift_byte = 0x80; } else { shift_byte = 0xC0; } first_bit = shift_byte & key_sets[m].y[0]; second_bit = shift_byte & key_sets[m].y[1]; third_bit = shift_byte & key_sets[m].y[2]; fourth_bit = shift_byte & key_sets[m].y[3]; key_sets[m].y[0] <<= shift_size; key_sets[m].y[0] |= (second_bit >> (8 - shift_size)); key_sets[m].y[1] <<= shift_size; key_sets[m].y[1] |= (third_bit >> (8 - shift_size)); key_sets[m].y[2] <<= shift_size; key_sets[m].y[2] |= (fourth_bit >> (8 - shift_size)); key_sets[m].y[3] <<= shift_size; key_sets[m].y[3] |= (first_bit >> (4 - shift_size)); first_bit = shift_byte & key_sets[m].z[0]; second_bit = shift_byte & key_sets[m].z[1]; third_bit = shift_byte & key_sets[m].z[2]; fourth_bit = shift_byte & key_sets[m].z[3]; key_sets[m].z[0] <<= shift_size; key_sets[m].z[0] |= (second_bit >> (8 - shift_size)); key_sets[m].z[1] <<= shift_size; key_sets[m].z[1] |= (third_bit >> (8 - shift_size)); key_sets[m].z[2] <<= shift_size; key_sets[m].z[2] |= (fourth_bit >> (8 - shift_size)); key_sets[m].z[3] <<= shift_size; key_sets[m].z[3] |= (first_bit >> (4 - shift_size)); for(n = 0; n < 48; n++) { shift_size = sub_key_permutation[n]; if(shift_size <= 28) { shift_byte = 0x80 >> ((shift_size - 1)%8); shift_byte &= key_sets[m].y[(shift_size - 1)/8]; shift_byte <<= ((shift_size - 1)%8); } else { shift_byte = 0x80 >> ((shift_size - 29)%8); shift_byte &= key_sets[m].z[(shift_size - 29)/8]; shift_byte <<= ((shift_size - 29)%8); } key_sets[m].temp[n/8] |= (shift_byte >> n%8); } } } void evaluate_message(unsigned char* message_piece, unsigned char* processed_piece, key_set* key_sets, int mode) { unsigned char initial_permutation[8], final_permutation[8]; unsigned char row, column, shift_byte; unsigned char ln[4], rn[4], er[6], ser[4], l[4], r[4]; int count, temp, key_position, shift_size; memset(initial_permutation, 0, 8); memset(processed_piece, 0, 8); for(count = 0; count < 64; count++) { shift_size = message_permutation[count]; shift_byte = 0x80 >> ((shift_size - 1)%8); shift_byte &= message_piece[(shift_size - 1)/8]; shift_byte <<= ((shift_size - 1)%8); initial_permutation[count/8] |= (shift_byte >> count%8); } for(count = 0; count < 4; count++) { l[count] = initial_permutation[count]; r[count] = initial_permutation[count + 4]; } for(temp = 1; temp <= 16; temp++) { memcpy(ln, r, 4); memset(er, 0, 6); for(count = 0; count < 48; count++) { shift_size = message[count]; shift_byte = 0x80 >> ((shift_size - 1)%8); shift_byte &= r[(shift_size - 1)/8]; shift_byte <<= ((shift_size - 1)%8); er[count/8] |= (shift_byte >> count%8); } if(mode == DECRYPTION_MODE) { key_position = 17 - temp; } else { key_position = temp; } for(count = 0; count < 6; count++) { er[count] ^= key_sets[key_position].temp[count]; } for(count = 0; count < 4; count++) { ser[count] = 0; } row = 0; row |= ((er[0] & 0x80) >> 6); row |= ((er[0] & 0x04) >> 2); column = 0; column |= ((er[0] & 0x78) >> 3); ser[0] |= ((unsigned char)array_a1[row*16 + column] << 4); row = 0; row |= (er[0] & 0x02); row |= ((er[1] & 0x10) >> 4); column = 0; column |= ((er[0] & 0x01) << 3); column |= ((er[1] & 0xE0) >> 5); ser[0] |= (unsigned char)array_a2[row*16 + column]; row = 0; row |= ((er[1] & 0x08) >> 2); row |= ((er[2] & 0x40) >> 6); column = 0; column |= ((er[1] & 0x07) << 1); column |= ((er[2] & 0x80) >> 7); ser[1] |= ((unsigned char)array_a3[row*16 + column] << 4); row = 0; row |= ((er[2] & 0x20) >> 4); row |= (er[2] & 0x01); column = 0; column |= ((er[2] & 0x1E) >> 1); ser[1] |= (unsigned char)array_a4[row*16 + column]; row = 0; row |= ((er[3] & 0x80) >> 6); row |= ((er[3] & 0x04) >> 2); column = 0; column |= ((er[3] & 0x78) >> 3); ser[2] |= ((unsigned char)array_a5[row*16 + column] << 4); row = 0; row |= (er[3] & 0x02); row |= ((er[4] & 0x10) >> 4); column = 0; column |= ((er[3] & 0x01) << 3); column |= ((er[4] & 0xE0) >> 5); ser[2] |= (unsigned char)array_a6[row*16 + column]; row = 0; row |= ((er[4] & 0x08) >> 2); row |= ((er[5] & 0x40) >> 6); column = 0; column |= ((er[4] & 0x07) << 1); column |= ((er[5] & 0x80) >> 7); ser[3] |= ((unsigned char)array_a7[row*16 + column] << 4); row = 0; row |= ((er[5] & 0x20) >> 4); row |= (er[5] & 0x01); column = 0; column |= ((er[5] & 0x1E) >> 1); ser[3] |= (unsigned char)array_a8[row*16 + column]; for(count = 0; count < 4; count++) { rn[count] = 0; } for(count = 0; count < 32; count++) { shift_size = intermediate_permutation[count]; shift_byte = 0x80 >> ((shift_size - 1)%8); shift_byte &= ser[(shift_size - 1)/8]; shift_byte <<= ((shift_size - 1)%8); rn[count/8] |= (shift_byte >> count%8); } for(count = 0; count < 4; count++) { rn[count] ^= l[count]; } for(count = 0; count < 4; count++) { l[count] = ln[count]; r[count] = rn[count]; } } for(count = 0; count < 4; count++) { final_permutation[count] = r[count]; final_permutation[4 + count] = l[count]; } for(count = 0; count < 64; count++) { shift_size = end_permutation[count]; shift_byte = 0x80 >> ((shift_size - 1)%8); shift_byte &= final_permutation[(shift_size - 1)/8]; shift_byte <<= ((shift_size - 1)%8); processed_piece[count/8] |= (shift_byte >> count%8); } } |
Custom Header File
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | #ifndef _DES_H_ #define _DES_H_ #define ENCRYPTION_MODE 1 #define DECRYPTION_MODE 0 typedef struct { unsigned char k[8]; unsigned char c[4]; unsigned char d[4]; } key_set; void generate_key(unsigned char* key); void generate_sub_keys(unsigned char* main_key, key_set* key_sets); void process_message(unsigned char* message_piece, unsigned char* processed_piece, key_set* key_sets, int mode); #endif |
Method 2: C Program To Implement DES Encryption Algorithm
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 | #include<stdio.h> int main() { int array_a1[30], array_a2[30], array_a3[30], array_a4[30], array_a5[30], array_a6[30], array_a7[30], array_a8[30]; int div, count, j, key, m, plaintext, temp, dec = 0; printf("\nEnter a Plain-Text value:\t"); scanf("%d", &plaintext); printf("\nEnter the Key:\t"); scanf("%d", &key); printf("\nEnter the Bit-Stream\n"); for(count = 0; count < plaintext; count++) { scanf("%d", &array_a1[count]); } div = plaintext / 2; temp = div - key; for(count = 0; count <= temp; count++) { array_a3[count] = 0; dec++; } dec = dec - 1; printf("Enter the Key Bit Stream\n"); for(count = 0; count < key; count++) { scanf("%d", &array_a3[dec++]); } for(count = 0; count < 2; count++) { printf("%d", array_a8[count]); } printf("Left Hand\n"); for(count = 0; count < div; count++) { array_a5[count] = array_a1[count]; printf("%d", array_a1[count]); } printf("Right Hand\n"); for(count = div; count < plaintext; count++) { array_a2[count] = array_a1[count]; printf("%d", array_a1[count]); } for(j = 0, m = div; j < dec, m < plaintext; j++, m++) { if(array_a2[m] == 1 && array_a3[j] == 1) { array_a6[j] = 0; } else if(array_a2[m] == 1 && array_a3[j] == 0) { array_a6[j] = m; } else { array_a6[j] = 0; } } printf("\nFirst XOR\n"); for(count = 0; count < div; count++) { printf("%d", array_a6[count]); } for(j = 0, m = 0; j < div, j++; j++, m++) { if(array_a5[m] = 1 && array_a6[j] == 1) { array_a4[j] = 0; } else if(array_a5[m] = 1 && array_a6[j] == 0) { array_a4[j] = m; } else if(array_a5[m] == 0 && array_a6[j] == 1) { array_a4[j] = 0; } } printf("\nSecond XOR\n"); for(count = 0; count < div; count++) { printf("%d", array_a4[j]); } return 0; } |
If you have any doubts or compilation errors in this C program to implement DES encryption algorithm, let us know about it in the comment section below. Find more about DES algorithm on Wikipedia.
The DES Algorithm is really difficult to understand.
What are the different types of algorithms which can be an alternative to DES Encryption algorithm?
There are many alternatives to the DES algorithm such as:
– BlowFish Algorithm
64 bits
– TwoFish Algorithm
256 bits
– RSA Algorithm
– AES (Advanced Encryption Standard) –
192, 256 and 128 bits
– Triple DES
68 bits, 112 bits
What about the MD5 Encryption algorithm? Is it not worth it?
This is such a simple DES algorithm. Thanks for this one. Amazing it is.
There is another very good algorithm which has been developed to improve the DES algorithm and it is IDEA which stands for International Date Encryption System.
Where is the output of the second method?
MD5 is not encryption, it is a hashing function.
HI,
can you suggest how to execute above code.
I see you wrote 3 program.