Implement a C program to decrypt a bmp image. Study the posted 8-bit-mini-DES al

Question

 Implement a C program to decrypt a bmp image.   Study the posted 8-bit-mini-DES algorithm posted, and study the code in miniDESv2.cpp.   The posted ePic.bmp was encrypted with this algorithm. Modify the program as necessary to create a decryption program and use it to decrypt the posted ePic file. Use a brute force key-guessing approach. Use your decryption program on ePic with every possible 8-bit key value from 0 to 255. This will generate 255 decryption candidates, then check the candidates visually with Windows File Explorer or some other viewer. You will know when you have the correct answer because it will be an image recognizable by a human. You may want to start off with your own super tiny binary files (like, 4 bytes with values 1234) for testing. Encrypt and decrypt your small test data first, because this is a lot easier to debug, also, you will know your program works ahead-of-time if you plan to compete for the fabulous prizes.   Requirements: 1) You must use the brute force approach described above.   2) You must FIRST write a program to generate the inverse function tables with C constant literal array initializer syntax format, and print out these inverse function tables for paper submission.   3) CLEARY indicate your final correct key value  4) Indicate your final substitution table function composition order. eg: f0  f1  f0 f3 or whatever it turns out to be (this part is way easier than it sounds). Resources: See the posted files “miniDES.cpp” and “ePic.bmp”. Binary file editor: “TinyHexer.exe”, posted earlier this semester.   Turn In: Paper printouts of:  1) Source code for inverse table generator program  2) Source code for decryption program  3) Inverse function tables printout  4) Key value  5) Inverse function composition order (list)  6) Decrypted output. Sample Output Your inverse tables Your Key Your inverse function composition order Your deciphered image           /*     Mini Data Encryption Standard (DES)          Dan Ross        Oct 2015      Performs a simplified version of DES encryption using an 8-bit key      1) Substitution - a discrete encryption function selected by the key     2) Transposition - a simple byte swap in this implementation     3) XOR - with the key     4) Repeat 3 more times       */  #include <iostream> #include <iomanip> #include <string.h> #include <fstream> #include <stdlib.h> #include <time.h> #pragma warning( disable : 4267) #pragma warning( disable : 4996) using namespace std;  /*  The Encryption Functions f[0] = { (0,  1)(1, 18)...(255,117) } f[1] = { (0,112)(1,103)...(255, 96) } etc... */ unsigned char f[4][256] = { //    0    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    {  1,  18, 121,  32, 127, 137, 132, 136, 144, 152, 159, 167, 175, 176, 178,   6, 149, 179, 186, 112,  59,  64,  12,   9,  81,  41,  29,  16,  10,   5,   0,  31,     //f[0]      76, 115, 165, 168,  74, 105,  48, 124, 172,  51, 182, 195,  63, 123,  38, 200, 205, 210,  28,  53, 212, 215, 217, 220, 109,  72,  99, 148, 158, 222, 229, 230,      57,  90, 104,  55,   8, 131, 169,  87, 180, 189, 213, 214, 194,  85, 133, 187,  73,  58,  66,  54, 141,  86,  15,  60,  82, 142,  47, 111, 157,  19,  36, 163,     166, 184,  71, 199, 201, 100,  39,  40,  95, 101, 139, 155,  62,  33, 177, 202,  25, 216, 223, 150, 227, 232, 235, 237, 238,  43, 240, 241,   2, 183, 122, 236,      24, 130, 161, 171,  23,  69, 181,  44, 190, 174, 219,  49,  75, 135, 208, 225, 234, 242, 243, 244,  67,  65, 146, 245, 239,  98,   7, 147, 120, 203, 207, 145,      80, 221, 160, 107,  61,  22,  92, 143, 193,  35, 185, 196, 204, 224, 231, 246, 248, 249, 250,  52, 251, 192, 197, 103, 119,  37,  77,  21, 129, 151, 170, 191,     198, 206, 209, 102,  11, 153,  88, 164, 226, 228, 116, 134, 233, 253, 126, 162,  42,   3, 138, 154,  78, 218, 247, 252, 211, 254,  96,  68, 110,  83, 125,  34,     128,  97, 106, 255, 156,   4,  26,  27,  30, 108,  56,  13,  93, 140,  17,  45, 173,  50, 118, 188,  91, 114,  46,  84,  89,  20,  14,  79,  94,  70, 113, 117},    { 112, 103, 224, 128, 140, 156,  60, 219,  25,  44, 213, 180, 187, 171, 169, 197, 228, 221, 236,  84, 164, 117, 225,  71,   1,  85,  27,  87,  99, 249, 118, 250,     //f[1]     214, 106, 239,  57,  92,  20, 138, 148, 181,  21, 185,  46, 226, 159, 240, 251,   2, 166, 252,  82, 253, 254,  65,   4, 105,  39, 177, 231, 255,  12,  64, 170,      53,  36, 182,  26,  22,  42,   9,  54, 119, 137, 124,  37, 155,  31,  86,  35, 107, 186, 216, 101,  33,  69, 116, 136, 134,  30,  49, 142, 143, 160, 179, 193,     220, 235, 176, 131,   0,  61,  47,  81, 108, 233,  18,  11,  28,  45,  95,  98, 162, 174, 175, 125,  67, 120, 194, 102, 201, 211,   8,  38,  62, 158, 163, 237,       3,  79, 150, 205, 238,  58, 241,  68, 178,  40,  14, 114, 123, 129, 144, 195, 203, 243, 100, 199,  76, 157,  50, 167,  24, 208, 212, 196, 217, 121,  41,  59,     115, 135, 127, 149, 184, 190,  29,  97, 189, 215,  90, 133,  83,  72, 244, 248,  94, 152,  23,  89, 139, 191, 200,  32,  91, 202, 227,  48, 209,  75,  80,   7,     154, 210, 126, 141, 232,  70, 218, 165, 198,  55, 110, 147,   5,   6,  51, 153, 173, 204, 161, 206,  43, 207, 188,  19, 223, 234,  10,  63,  52,  66,  34,  93,     130, 242,  88, 183,  13, 146, 230, 229,  17, 132, 168, 245, 246, 145, 111,  74,  16,  56, 104, 247, 109, 113,  73, 192, 222,  77, 172,  15, 122, 151,  78,  96},    {  71,  68,  46, 109, 126, 147, 179,  62, 183, 195, 213,  67,  83, 191,  11,  37, 118, 193, 216,  14, 186,  73, 101, 114, 140, 142, 231,   0, 205, 232,  12,  40,     //f[2]     123,  32, 137,  23,  25,  38, 132, 143,  27, 107, 121,  94, 203,  82, 131, 163, 196, 206, 149, 218,  50,  72,  81, 146, 111, 100, 219, 110,  75, 127,  44, 182,     155,  48,  76, 189,  79, 210,  56, 116, 164, 198,  20, 209, 214, 113, 138,   1, 220, 221,  34, 158, 225, 229,  86,  98, 234,   3,  42, 236, 237, 238, 241, 243,      16,  57,   9,   8,  28,  33,  13,   7,  80,  96, 103, 159,  17, 228, 150, 177, 184, 212, 239, 141, 244, 144,  90,  78, 171, 106, 152,  55, 176,  85, 122,  10,      54, 102,  26,  60, 139, 148, 153,  53,   4,  65,  84, 161, 169,  49, 187,  58, 222, 224, 226, 130, 136,  43, 245, 207,  35, 157, 246, 248, 105,  21, 249, 250,     251, 252, 253, 133,  41,  47,   6, 247, 254, 240, 128, 162,  63,  97, 173,  66,  15, 104,  69, 108, 119,  52, 129, 167, 170, 115,  59, 175, 180, 185, 145,  89,     135, 181,  22, 165, 112,   5, 124, 160,  87, 192, 200,  92, 201, 215,  30, 217,  51, 174, 223, 230,  70, 233, 227, 235, 178, 197,  99, 204, 242,  19, 255,  93,      64,  29,  18,  39,  95,  45, 151, 188, 190, 117, 194,  74, 199,  88, 168, 202, 125, 154, 208,  36, 134, 166,  77,  31, 156, 172,   2, 211, 120,  61,  24,  91},     { 224, 102, 161,  74, 213, 234, 212,  69, 246,  30,  64, 107,  66,  81,  82, 123,  76, 132, 112, 136, 105, 129, 194, 151, 215,  40, 120,  49,  83, 148, 100, 131,    //f[3]       15,  65,  43, 134, 174, 189, 216, 138, 220, 214, 223, 225, 142,  71, 205,  48, 217, 227,  34,  12, 169,  17, 179, 237, 238, 218,   3,  16,  41,  61, 109,  45,      198, 239, 119,  92,  25, 230, 243, 244, 247, 248, 249, 250, 150, 253,  58, 236,   8,  94, 121, 167, 251,  52,  44,  97,  21,  36,   5,  42, 114,  32,  95, 166,      196, 201, 219,  26, 101,  57,  37, 140,  46,   7, 125,  77, 153, 171, 187, 203, 204,  56,  70, 207,  67, 115, 135, 173,  90, 195, 197, 209, 210, 211, 192, 221,      226, 157, 162,  20,  96, 147, 199,  98, 126,  80, 178, 182, 228, 103, 229, 128, 156,  13, 144,  23,  51, 139, 172, 183,  63, 110, 202, 208, 231,  35, 235, 155,      241, 252,  27, 254, 255,  68, 133,   9,  62,   1,  99,  87, 108, 130, 137,  54,  84, 149,   0, 104, 113,  93, 127, 145,  79, 154,  14, 164,  22, 143, 170, 177,      180, 181, 163, 186,  60, 124, 191, 193, 190,  33,  53, 175,  91, 240, 117, 242, 245, 176, 185,  29,  73, 152, 233,  18, 111, 116, 146,  75,  78,  89, 141, 158,      168, 200, 222,  50,  85,  88, 184,  86,  55, 232, 122,   6,  10,  38,   4,  39, 106, 118,   2,  19,  47, 160,  59,  24,  11,  31,  72, 165, 188, 206,  28, 159} };   /* The INVERSE Encryption Functions    Please fill this programmatically using fill_fi() fi[0] = { (0,  30)(1,   0)...(255, 227) } fi[1] = { (0, 100)(1,  24)...(255,  60) } etc... */ unsigned char fi[4][256];   // fill and print the inverse function table void fill_fi() {     // YOU WRITE THIS PLEASE }   /* Swaps the high and low nibbles of a byte */ unsigned char swapbytes(unsigned char cIn) {     unsigned char lownibble, highnibble, cOut = 0;      lownibble = cIn & 0x0F;     highnibble = cIn & 0xF0;      cOut = highnibble >> 4;     cOut = cOut | (lownibble << 4);      return cOut; }   /* Performs miniDES style encryption  You will need to write a decrypt function */ unsigned char encrypt(unsigned char w, unsigned char key) {     // intermediate values in the process     unsigned char x0, y0, z0;             unsigned char x1, y1, z1;     unsigned char x2, y2, z2;     unsigned char x3, y3, z3;      // get base_4 digit values of key by parsing bits... every 2 bits is a base_4 digit     unsigned char p, q, r, s;     // key = s x 4^3  +  r x 4^2  +  q x 4^1  +  p x 4^0     p = (key & 0x03);     q = (key & 0x0C) >> 2;     r = (key & 0x30) >> 4;     s = (key & 0xC0) >> 6;          // Stage 0     x0 = f[s][w];         // substitution     y0 = swapbytes(x0);   // transposition     z0 = y0 ^ key;        // XOR      // Stage 1     x1 = f[r][z0];     y1 = swapbytes(x1);     z1 = y1 ^ key;      // Stage 2     x2 = f[q][z1];     y2 = swapbytes(x2);     z2 = y2 ^ key;      // Stage 3     x3 = f[p][z2];     y3 = swapbytes(x3);        z3 = y3 ^ key;              return z3;  }   /* Yo, sup? */ void main() {     char c;     // the byte to encrypt      // open source file     ifstream fin("pPic.bmp", ios_base::binary);     if (!fin) { cerr << "Input file could not be opened "; exit(1); }      // open destination file     ofstream fout("ePic.bmp", ios_base::binary);     if (!fout) { cerr << "Output file could not be opened "; exit(1); }      // read, encrypt, write     while (!fin.eof())     {         fin.read(&c, 1);         if (!fin.eof())         {             //cout << (int) w << endl;             c = encrypt(c, 42);             // Not the real key, you must brute force guess the real key             fout.write(&c, 1);         }     }      fin.close();     fout.close();      /*     // handy code to build a filename string for iterative (brute force) crack     char filename[30];     char numstr[10];          strcpy(filename, "pPic");     itoa(key, numstr, 10);     strcat(filename, numstr);     strcat(filename, ".bmp");     */ } 

Explanation / Answer

Encryption is a method used to protect data from in

truders during transmission. The idea of data

encryption is to scramble data using a specific key

, so attackers would need to know the key to

decrypt the data. The reverse of data encryption is

called decryption. Decryption algorithm will

recreate the original data file. For example, a naï

ve encryption of an ASCII file is to encrypt each

character just by adding 1 to each character. That

is replacing each character by its successor in

the ASCII table. So ‘a’

‘b’ , ‘b’

‘c’, ..., ‘t’

’u’. So the word “bat” would be encrypted as

“cbu”. Now applying the decryption algorithm (or ju

st subtracting one from each of the

encrypted characters “cbu” or by replacing with its

predecessor will produce the original word

“bat”. Although there are number of research result

s available on image encryption, our goal in

this assignment is not to use one of the more advan

ced algorithms, but try out number of simple

algorithms, some of your choosing, that would allow

us to work with binary files, do some bit

manipulations, encode and decode image files. For s

implicity we will consider only the

uncompressed image formats like BMP

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