Need C++ coding Help Encryption and Decryption Using Substitution and Caesar Cipher.

Question

Program Specification:

Using the techniques presented during this semester create a complete C++ program to emulate an

Encryption/Decryption Machine. The machine will be capable of the following:

 Encrypt a string entered by the user

 Choose between two different encryption methods

 Decrypt a string entered by the user

 Choose between two different decryptions methods

 Decrypt without knowing the encryption method (provide all possible outputs)

The interface must be professional and fully intuitive to the user

The program will be menu driven.

The program will use a class to define and implement each of the methods as member functions and will

store the original string and the encrypted/decrypted strings as data members.

In addition to using a class you must also use all the major structures we used this semester including:

Selection statements (if, if-else, switch) the appropriate one(s) of course

Loops (while, for, do-while) the appropriate one(s) of course

Standard Libraries (don’t recreate the wheel)

Functions

Arrays

The two encryption/decryption methods are:

Substitution cipher

Caesar cipher

You will need to research each and determine how to implement them. Remember in the case of the

Caesar cipher there are 25 possible shifts, you must be able to choose or test for all 25 options.

Answer 1

Here are the encryption and decryption methods that you need. Work on the menus LATER!!!

using namespace std;

#include <iostream>

#include <string>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <ctype.h>

#define ALPHABET ("ABCDEFGHIJKLMNOPQRSTUVWXYZ")

typedef

class Cipher

{

public:

void EncryptCaesar(char * inbuff, int shiftNum, bool dir, char * outbuff)

{

char key[27];

if (dir)

{

memset(key,0,27);

strcpy(key,ALPHABET+shiftNum);

memcpy(key+26-shiftNum,ALPHABET,shiftNum);

}

else

{

memset(key,0,27);

memcpy(key,ALPHABET+26-shiftNum,shiftNum);

memcpy(key+shiftNum,ALPHABET,26-shiftNum);

}

cout << "key = >" <<key <<"<" << endl;

int N = strlen(inbuff);

memset(outbuff,0,N+1);

char chChar='?';

for (int iLoop=0; iLoop<N; iLoop++)

{

chChar = inbuff[iLoop];

if (isalpha(chChar))

{

outbuff[iLoop] = key[(toupper(chChar))-65];

}

else

{

outbuff[iLoop] = chChar;

}

}

}

void DecryptCaesar(char * inbuff, int shiftNum, bool dir, char * outbuff)

{

char key[27];

if (dir)

{

memset(key,0,27);

strcpy(key,ALPHABET+shiftNum);

memcpy(key+26-shiftNum,ALPHABET,shiftNum);

}

else

{

memset(key,0,27);

memcpy(key,ALPHABET+26-shiftNum,shiftNum);

memcpy(key+shiftNum,ALPHABET,26-shiftNum);

}

cout << "key = >" <<key <<"<" << endl;

int N = strlen(inbuff);

memset(outbuff,0,N+1);

char chChar='?';

for (int iLoop=0; iLoop<N; iLoop++)

{

chChar = inbuff[iLoop];

if (isalpha(chChar))

{

char * targetChar = strchr(key,toupper(chChar));

int iIndexPos = targetChar-key;

outbuff[iLoop] = ALPHABET[iIndexPos];

}

else

{

outbuff[iLoop] = chChar;

}

}

}

void EncryptSubstitution(char * inbuff, char * mixedAlphabetKey, char * outbuff)

{

int N = strlen(inbuff);

memset(outbuff,0,N+1);

char chChar='?';

for (int iLoop=0; iLoop<N; iLoop++)

{

chChar = inbuff[iLoop];

if (isalpha(chChar))

{

outbuff[iLoop] = mixedAlphabetKey[(toupper(chChar))-65];

}

else

{

outbuff[iLoop] = chChar;

}

}

}

void DecryptSubstitution(char * inbuff, char * mixedAlphabetKey, char * outbuff)

{

int N = strlen(inbuff);

memset(outbuff,0,N+1);

char chChar='?';

for (int iLoop=0; iLoop<N; iLoop++)

{

chChar = inbuff[iLoop];

if (isalpha(chChar))

{

char * targetChar = strchr(mixedAlphabetKey,toupper(chChar));

int iIndexPos = targetChar-mixedAlphabetKey;

outbuff[iLoop] = ALPHABET[iIndexPos];

}

else

{

outbuff[iLoop] = chChar;

}

}

}

void Decrypt(char * inbuff)

{

}

} *TCipher;

#define CIPHER_SIZE (sizeof(Cipher))

int main()

{

char inbuff[255];

char outbuff[255];

char str[255];

strcpy(inbuff,"The quick brown fox jumped over the lazy dogs.");

Cipher cipher;

cipher.EncryptCaesar(inbuff,5,false,outbuff);

cout << outbuff << endl;

cipher.DecryptCaesar(outbuff,5,false,str);

cout << str << endl;

char strKey[27];

strcpy(strKey,"SUPERMANBCDFGHIJKLOQTVWXYZ");

cipher.EncryptSubstitution(inbuff,strKey,outbuff);

cout << outbuff << endl;

memset(str,0,255);

cipher.DecryptSubstitution(outbuff,strKey,str);

cout << str << endl;

char strMsg[27];

strcpy(strMsg,"UIF RVJDL CSPXO GPY KVNQFE PWFS UIF MBAZ EPHT.");

for (int shiftLoop=0; shiftLoop<26; shiftLoop++)

{

memset(outbuff,0,255);

cipher.DecryptCaesar(strMsg,shiftLoop,true,outbuff);

cout << "shift # = " <<shiftLoop << " possible decrypt " << outbuff << endl;

}

}