Write a program in Python or C++ that has TWO functions: Function One is called:

Question

Write a program in Python or C++ that has TWO functions:

Function One is called: _encrypt

Function Two is called: _decrypt

Function one takes plain text, and assesses the indexed value of each letter in the string. For example, a=1, b=2. It then adds three to the indexed value, and produces encrypted text, based off of the plain text.

Function two reverses this.

Here is sample output:

_encrypt('how do you do')

Unsecured: howdoyoudo

Secured: lsahscsyhs

_decrypt('lsahscsyhs')

Unsecured: lsahscsyhs

Secured: howdoyoudo

Explanation / Answer

Program code:

// EncryptionDecryption.cpp : Defines the entry point for the console application.

//

#include "stdafx.h"

#include <iostream>

#include <string>

using namespace std;

int size=0;

//declare the functions

string _encrypt(string s,char *encrypt, char *in);

void _decrypt(string s, char *encrypt,char * in);

int main()

{

     //char array

     char in[26]={'a','b','c','d','e', 'f', 'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};

     char encrypt[26];

     //strings

     string s;

     string st;

     char p[200];

     int k=0;

     //encrypt techinque

     for(int i=0;i<26;i++)

     {

          if((i+4)<26)

          {

              encrypt[i]=in[i+4];

          }

          else

          {

              encrypt[i]=in[k];

              k++;

          }       

     }  

     cout<<"Enter a string: ";

     getline(cin,s);

     //remove the spaces in s

     for(int i=0; i<s.length(); i++)

     {

          if(s[i] == ' ')

              s.erase(i,1);

     }

     cout<<endl;

     //call encryption store it in a string st

     st=_encrypt(s,encrypt, in);

     //call decrypt function

     _decrypt(st, encrypt, in);

     system("pause");

     return 0;

}

//definition of _encrypt function and returns a string

string _encrypt(string s,char *encrypt, char *in)

{

     int n=0;

     char c[200];

     //convert string to character

     for(int i=0;i<s.size();i++)

     {

          c[n]=s.at(i);

          n++;

     }

     size=n;

     int k=0;

     n=0;

     char ch[200];

     //logic to encrypt

     for(int i=0; i<size;i++)

     {

          n=0;        

          n++;

          while(n<26)

          {

              if(c[i]==in[n])

              {

                   ch[i]=encrypt[n];

              }

              n++;             

          }           

     }

     //print the output

     cout<<"Unsecured: "<<s<<endl;

     cout<<"Secured: ";

     for(int i=0;i<size;i++)

     {

          s.at(i)=ch[i];

          cout<<ch[i];

     }

     cout<<endl;

     //return the modified string

     return s;

}

//defintion of _decrypt

void _decrypt(string s,char *encrypt, char *in)

{

     int n=0;

     char c[200];

     //convert string to char array

     for(int i=0;i<s.size();i++)

     {

          c[n]=s.at(i);

          n++;

     }

     int k=0;

     n=0;

     char ch[200];

     //logic to decrypt

     for(int i=0; i<size;i++)

     {

          n=0;        

          n++;

          while(n<26)

          {

              if(c[i]==encrypt[n])

              {

                   ch[i]=in[n];

              }

              n++;             

          }           

     }

     //print the output

     cout<<"Unsecured: "<<s<<endl;

     cout<<"Secured: ";

     for(int i=0;i<size;i++)

     {

          cout<<ch[i];

     }

     cout<<endl;

}

---------------------------------------------------------------------------------------

Sample output:

Enter a string: how do you do

Encryption:

_encrypt(howdoyoudo);

Unsecured: howdoyoudo

Secured: lsahscsyhs

Decryption:

_decrypt(lsahscsyhs);

Unsecured: lsahscsyhs

Secured: howdoyoudo

Press any key to continue . . .

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