Question

I need to complete this C++ program. The instructions are in the comments inside the code below:

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

Original string is: this is a secret!

Encypted string is: uijt!jt!b!tfdsfu"

Decrypted string is: this is a secret!

//Encoding program

//Pre-_____?

//other necessary stuff here

int main()

{

//create a string to encrypt using a char array

cout<< "Original string is: "<<string<<endl;

encrypt(string);

cout<< "Encrypted string is: "<<string<<endl;

decrypt(string);

cout<<"Decrypted string is: "<<string<<endl;

return 0;

}

void encrypt(char e[])

{

//Write implementation function encrypt

}

void decrypt(char *ePtr)

{

//Write implementation function decrypt

}

Answer 1

Original string is: this is a secret!

Encypted string is: uijt!jt!b!tfdsfu"

Decrypted string is: this is a secret!

Here we can observe that Substitution encryption technique has been used with key as 1. So a will be repcaed with b b with c and so on. Here each character in plain text will be replaced by its next character in ascii table.

#include <iostream>
using namespace std;

void encrypt(char e[]);
void decrypt(char *ePtr);

int main()

{

//create a string to encrypt using a char array
char string[100]="this is a secret!";

cout<< "Original string is: "<<string<<endl;

encrypt(string);

cout<< "Encrypted string is: "<<string<<endl;

decrypt(string);

cout<<"Decrypted string is: "<<string<<endl;

return 0;

}

void encrypt(char e[])

{

//Write implementation function encrypt
int i=0;
while(e[i]!='\0')
{
e[i]=(char)(((int)e[i]+1)%128);
i=i+1;
}

}

void decrypt(char *ePtr)

{

//Write implementation function decrypt
while(*ePtr!='\0')
{
*ePtr=(char)(((int)*ePtr+127)%128);
ePtr++;
}

}