Question

Please decrypt the following encrypted message using c++ coding language, using the CLASS method :

Y [ZU [ XZWZ \ XXZjZ [ [ WWVWU

Ogaqkxpgbqbfiof! Cyw'ss bun!

Zqksxl cywd lnepwvs uozneh.

You are required to programmatically implement an automatic decryption tool, using only C++ as your programming language. Your program must show how all steps of the decryption process are resolved, for any marks to be awarded. This is similar to the decryption method being done manually, by hand on paper, showing all steps and working as to how the final answer is obtained.

‐ The entire operation of the program must use classes and its respective methods (class functions). Functions that are not implemented as class methods, except for the main function, will be disregarded for marking.

‐ Any numerical conversions must be done directly e.g. binary to octal, without the use of decimal. The use of intermediary bases will be disregarded for marking.

‐ An input argument named “‐silent” (without the quotation marks), is required to be implemented. This is to allow for a driver function to be called and only for the final answer to be outputted to the system command prompt. The format for this argument, coupled with the text file argument, can be seen below: program_name -input encrypted.txt -silent.

Qjc mgabiy nfx vmz-djrhkfalfq.

Xnjfx ai qjvi viqi uat pgw odjwp.

Answer 1

#include "bits/stdc++.h"
using namespace std;
class playfair {
public:
        string msg; char n[5][5];
        void play( string k, string t, bool m, bool e ) {
                createEncoder( k, m );
                getText( t, m, e );
                if ( e )
                        play( 1 );
                else
                        play( -1 );
                print();
        }
private:
        void play( int dir ) {
                int j, k, p, q;
                string nmsg;
                for ( string::const_iterator it = msg.begin(); it != msg.end(); it++ ) {
                        if ( getPos( *it++, j, k ) )
                                if ( getPos( *it, p, q) ) {
                                        //for same row
                                        if ( j == p ) {
                                                nmsg += getChar( j, k + dir );
                                                nmsg += getChar( p, q + dir );
                                        }
                                        //for same column
                                        else if ( k == q ) {
                                                nmsg += getChar( j + dir, k );
                                                nmsg += getChar( p + dir, q );
                                        } else {
                                                nmsg += getChar( p, k );
                                                nmsg += getChar( j, q );
                                        }
                                }
                }
                msg = nmsg;
        }
        void print() //print the solution {
        cout << "\n\n Solution:" << endl;
        string::iterator it = msg.begin(); int count = 0;
        while ( it != msg.end() ) {
                cout << *it;
                it++;
                cout << *it << " ";
                it++;
                if ( ++count >= 26 )
                        cout << endl;
                count = 0;
        }
        cout << endl << endl;
};
char getChar( int a, int b ) { //get the characters
        return n[ (b + 5) % 5 ][ (a + 5) % 5 ];
}
bool getPos( char l, int &c, int &d ) { //get the position
        for ( int y = 0; y < 5; y++ )
                for ( int x = 0; x < 5; x++ )
                        if ( n[y][x] == l ) {
                                c = x;
                                d = y;
                                return true;
                        }
        return false;
}
void getText( string t, bool m, bool e ) { //get the original message
        for ( string::iterator it = t.begin(); it != t.end(); it++ ) {
                //to choose J = I or no Q in the alphabet.
                *it = toupper( *it );
                if ( *it < 65 || *it > 90 )
                        continue;
                if ( *it == 'J' && m )
                        *it = 'I';
                else if ( *it == 'Q' && !m )
                        continue;
                msg += *it;
        } if ( e ) {
                string nmsg = ""; size_t len = msg.length();
                for ( size_t x = 0; x < len; x += 2 ) {
                        nmsg += msg[x];
                        if ( x + 1 < len ) {
                                if ( msg[x] == msg[x + 1] ) nmsg += 'X';
                                nmsg += msg[x + 1];
                        }
                }
                msg = nmsg;
        }
        if ( msg.length() & 1 )
                msg += 'X';
}
void createEncoder( string key, bool m ) { //creation of the key table
        if ( key.length() < 1 )
                key = "KEYWORD";
        key += "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        string s = "";
        for ( string::iterator it = key.begin(); it != key.end(); it++ ) {
                *it = toupper( *it );
                if ( *it < 65 || *it > 90 )
                        continue;
                if ( ( *it == 'J' && m ) || ( *it == 'Q' && !m ) )
                        continue;
                if ( s.find( *it ) == -1 )
                        s += *it;
        }
        copy( s.begin(), s.end(), &n[0][0] );
}
int main( int argc, char* argv[] ) {
        //main can be changed according to the needs of the ques, since I don't have the 
        // file for decrypting, 
        



        // string k, i, msg;
        // bool m, c;
        // cout << "Encrpty or Decypt? ";
        // getline( cin, i );
        // c = ( i[0] == 'e' || i[0] == 'E' );
        // cout << "Enter a key: ";
        // getline( cin, k);
        // cout << "I <-> J (Y/N): ";
        // getline( cin, i );
        // m = ( i[0] == 'y' || i[0] == 'Y' );
        // cout << "Enter the message: ";
        // getline( cin, msg );
        // playfair pf;
        // pf.play( k, msg, m, c );
        // return system( "pause" );



}