Encryption-Decryption Program

Overview

This C++ program provides a menu-driven interface for encrypting and decrypting text using three classic ciphers:

• Caesar Cipher
• XOR Cipher
• Vigenère Cipher

The user can select encryption or decryption, choose a cipher, and provide the required keys.

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How to Use

1. Run the Program:
   Compile and run the code. You’ll be prompted to choose between encryption and decryption.

2. Select Cipher:
   Choose one of the three supported ciphers.

3. Input Data:

   • Enter the sentence to encrypt or decrypt.
   • Enter the required key (shift for Caesar, integer for XOR, keyword for Vigenère).

4. View Result:
   The program displays the encrypted or decrypted result.

5. Repeat or Exit:
   Choose to run again or exit the program.

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Function Documentation

Caesar Cipher

Caesar_Cipher_Enc
Encrypts a string using the Caesar cipher.

string Caesar_Cipher_Enc(string sentence, int shift)

• sentence: The input text to encrypt.
• shift: The integer shift value.
• Returns: Encrypted string.

Caesar_Cipher_Dec
Decrypts a string using the Caesar cipher.

string Caesar_Cipher_Dec(string sentence, int shift)

• sentence: The encrypted text.
• shift: The integer shift value.
• Returns: Decrypted string.

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XOR Cipher

XOR_Cipher
Encrypts or decrypts a string using XOR operation (symmetric).

string XOR_Cipher(string sentence, int key)

• sentence: The input text.
• key: Integer key value.
• Returns: Encrypted or decrypted string.

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Vigenère Cipher

Vigenere_Cipher_Enc
Encrypts a string using the Vigenère cipher.

string Vigenere_Cipher_Enc(string sentence, string keyword)

• sentence: The input text to encrypt.
• keyword: The keyword used for encryption.
• Returns: Encrypted string.

Vigenere_Cipher_Dec
Decrypts a string using the Vigenère cipher.

string Vigenere_Cipher_Dec(string sentence, string keyword)

• sentence: The encrypted text.
• keyword: The keyword used for decryption.
• Returns: Decrypted string.

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Main Menu Flow

• Prompts for encryption or decryption.
• Prompts the user to select one of the three ciphers.
• Requests the sentence and relevant key/keyword.
• Calls the appropriate function and outputs the result.
• Allows the user to run the program again or exit.

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Notes

• Only alphabetic characters are ciphered; non-letters are preserved.
• For XOR, encryption and decryption are the same operation.
• Input validation is basic; invalid choices exit the loop or prompt for re-entry.

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Example

Enter your choice:
1. Encryption
2. Decryption
>> 1

Enter type of Encryption you want:
1. Caesar Cipher
2. XOR Cipher
3. Vigenere Cipher
>> 1

Enter a sentence you want to Encryption : Hello World!
Enter the shift (number): 3

Encrypted Sentence: Khoor Zruog!