**XOR (Exclusive-Or)** is a boolean logic operation that we use widely in cryptography. The following table shows the XOR results according to different inputs: 

# Cryptography
It is essential to lay down the fundamentals of cryptography before diving into how XOR encryption and decryption works. **Cryptography** secures communication between two end-points. For example, if A wants to send a message to B, both A and B require a key to encrypt and decrypt. The steps involved are as follows:

1. The plaintext is the original text message that A wants to send to B.

2. The ciphertext is the text encrypted by A using the key. 

3. B will decrypt the ciphertext back to the plaintext using the key and read the message. 

The illustration below depicts the steps mentioned above: 


# Example
The code below shows an example of XOR encryption and decryption using C++. 

For the code below, we use the key, `U` to encrypt and decrypt. The `plaintext,` "Hello! How are you?" is passed through the `XorOp` function. The XOR operation takes the first bit of the plaintext and the key and returns the corresponding ciphertext. We call the `XorOp` function again to convert the ciphertext back to plaintext. XOR has the property of self-inverse, which makes it suitable for cryptography. The code is as follows:

#include <iostream>
#include<bits/stdc++.h>

using namespace std;

//Function for Encryption and Decryption
void XorOp (char text[], int length){
  //Key 
  char key = 'U';
  //XOR Operation
  for (int i=0; i<length; i++){
    text[i] = text[i]^key;
    cout << text[i];
  }
}


int main() {
  //Plaintext
  char plaintext[] = "Hello! How are you?";
  int length = strlen(plaintext);

  //Encryption
  cout << "Ciphertext: ";
  XorOp(plaintext, length);
  cout << endl;

  //Decryption
  cout << "Plaintext: ";
  XorOp(plaintext, length);
  cout << endl;
  return 0;
}

What are XOR encryption and decryption?

XOR (Exclusive-Or) is a boolean logic operation that we use widely in cryptography. The following table shows the XOR results according to different inputs: 

Input A	Input B	A XOR B Output
1	1	0
1	0	1
0	1	1
0	0	0