Question

Project Description:
In groups of four students, implement (New Encryption Algorithm) character oriented and apply it using any programming Language that you are familiar with to encrypt and decrypt your name.

Your work should cover:

1. Create the algorithm and explain (encryption-decryption) using block diagram.
2. Mention whether will you use the keys or not in your algorithm.
3- If you will use keys, explain how to generate the keys.
2. Display the generated keys
3. Encrypt your name
4. Display the plain text
5. Display the cipher text
6. Decrypt the cipher text to get the plaintext.

Answer 1

#include <iostream>
#include <stdlib.h>
#include <ctime>
using namespace std;
  
// This function receives text and shift and
// returns the encrypted text
string encrypt(string text, int s)
{
string result = "";
  
// traverse text
for (int i=0;i<text.length();i++)
{
// apply transformation to each character
// Encrypt Uppercase letters
if (isupper(text[i]))
result += char(int(text[i]+s-65)%26 +65);   //Calculate: Y = (X + K) % 26 (step 2 in algorithm)
  
// Encrypt Lowercase letters
else
result += char(int(text[i]+s-97)%26 +97);   //Calculate: Y = (X + K) % 26 (step 2 in algorithm)
}
  
// Return the resulting string
return result;
}

// This function receives text and shift and
// returns the decrypted text
string decrypt(string text, int s)
{
string result = "";
  
// traverse text
for (int i=0;i<text.length();i++)
{
// apply transformation to each character
// decrypt Uppercase letters
if (isupper(text[i]))
result += char(int(text[i]-s-65)%26 +65); //Calculate: Y = (X - K) % 26 (step 2 in algorithm)
  
// Encrypt Lowercase letters
else
result += char(int(text[i]-s-97)%26 +97);   //Calculate: Y = (X - K) % 26 (step 2 in algorithm)
}
  
// Return the resulting string
return result;
}
// Driver program to test the above function
int main()
{
string text;
   cout<<"Enter your Name :";
cin>>text;
cout << "Text : " << text;
int key;
srand((unsigned) time(0)); //To avoid the repetitive sequence, you must set the seed as an argument to the srand() method.
key = rand() % 20+1;         // generate a random key in a range of 1 to 20
   cout<<"\nKey ="<<key;
string cipherText = encrypt(text, key); // encrypt function is called with randomly generated key
string plainText = decrypt(cipherText, key); // decrypt function is called with previously randomly generated key
cout << "\nCipher Text: " << cipherText;
   cout << "\nOriginal Text: " << plainText;
return 0;
}

algorithm of encryption

For every letter in the message M :

1. Convert the letter into the number that matches its order in the alphabet starting from 0, and call this number X.
( A=0, B=1, C=2, ...,Y=24, Z=25)

2. Calculate: Y = (X + K) % 26

3. Convert the number Y into a letter that matches its order in the alphabet starting from 0.

algorithm of decryption

For every letter in the message M :

1. Convert the letter into the number that matches its order in the alphabet starting from 0, and call this number X.
( A=0, B=1, C=2, ...,Y=24, Z=25)

2. Calculate: Y = (X - K) % 26

3. Convert the number Y into a letter that matches its order in the alphabet starting from 0.

Main Function   encrypt function

decrypt function

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