Cryptit Guide

Files in the Program:

• main.py: The script that controls the execution of the encryption and decryption processes.
• cryptit.py: Contains the core logic for encryption and decryption.
• utils.py: Utility functions for handling encryption and decryption operations.
• text.txt: The input file containing plain text that will be encrypted.
• key.txt: Contains a 128-digit encryption key used by the encryption and decryption algorithm.
• cipher.txt: Contains encrypted text from running the encryption algorithm with key.txt on text.txt.
• output.txt: Contains the decrypted text from running the decryption algorithm with key.txt on cipher.txt.

Step-by-Step Instructions for Usage:

Step 1: Set Up Your Environment

Ensure all the necessary Python files (main.py, cryptit.py, utils.py) and the text files (text.txt, key.txt, cipher.txt, output.txt) are in the same directory.

Step 2: Input Preparation

• The key.txt file should already contain a 128-digit encryption key, which the program uses for encryption and decryption. However, you can also use any valid 128-digit encryption key.
• The text.txt file should contain the plain text you want to encrypt.

Step 3: Running the Program for Encryption

1. Ensure that the plain text is available in text.txt.
2. Ensure that a 128-digit encryption key is available in key.txt.
3. Run the main.py file from the terminal or command line:

   python3 main.py

   or

   python main.py

4. The main menu is displayed with three options:

   1. Encrypt a message
   2. Decrypt a message
   3. Exit Program
   

5. Choose option 1 to encrypt a message.
6. You will be prompted to provide the name of the text file you want to encrypt.
   • Provide your own file or use the example file text.txt.
7. You will be prompted to provide the name of the key text file.
   • Provide your own file or use the example file key.txt.
8. You will be prompted to provide the name of the text file to which the encrypted cipher text will be outputted.
   • Provide your own file or use the example file cipher.txt.
9. Success! Your message has been encrypted. Please take note of your encryption key and store it safely.

Step 4: Running the Program for Decryption

1. Ensure that the cipher text is available in cipher.txt.
2. Ensure that a 128-digit decryption key is available in key.txt.
3. Run the main.py file from the terminal or command line:

   python3 main.py

   or

   python main.py

4. The main menu is displayed with three options:

   1. Encrypt a message
   2. Decrypt a message
   3. Exit Program
   

5. Choose option 2 to decrypt a message.
6. You will be prompted to provide the name of the text file you want to decrypt.
   • Provide your own file or use the example file cipher.txt.
7. You will be prompted to provide the name of the key text file.
   • Provide your own file or use the example file key.txt.
8. You will be prompted to provide the name of the text file to which the decrypted original plain text will be outputted.
   • Provide your own file or use the example file output.txt.
9. Success! Your message has been decrypted. You will be able to view the decrypted message in your output file.

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Notes

• Ensure you do not lose your 128-digit encryption key; without it, you will not be able to decrypt the message.
• This program expects all file paths to be relative or available in the same directory as the Python scripts.

Cryptit Documentation

Cryptit is a command-line application that allows users to easily encrypt and decrypt files using symmetric encryption. In symmetric encryption, the same key is used for both encryption and decryption, ensuring data security and efficiency. Cryptit employs three cipher techniques to perform encryption: the Caesar cipher, the Pair Swap cipher, and the Group Swap cipher. By combining these ciphers with the key, Cryptit creates a customized encryption process that applies different cipher techniques in a key-determined order. This layered approach adds complexity to the encryption, making it difficult for unauthorized users to access the original data and ensuring that only someone with the correct key can decrypt it.

Cipher Techniques

1. Caesar Cipher: Shifts each letter in the message by a specific number of positions in the alphabet. The shift value (X) is determined by the key and the tasks created during the encryption action task set creation.

2. Pair Swap Cipher: Swaps each pair of letters in the message. For instance, the word "Apples" becomes "pAlpse" after the pairs are swapped.

3. Group Swap Cipher: Divides the message into groups of a specific size (X) and swaps these groups with each other.

Key and Task Set

The key used for both encryption and decryption is transformed into an encryption action task set—an array of encryption tasks applied sequentially to the message. Applying the correct encryption action task set in reverse order to the cipher text restores the original message. The 128-digit key is converted into an array of 128 digits, where each element is a counter equal to its corresponding digit. The algorithm iterates through this array, applying ciphers based on modulus operations to determine the cipher type (Caesar, Pair Swap, or Group Swap).

Future Improvements

A significant improvement would be to reduce the size of the encryption action task set. Currently, the task set can become large, up to 9×128 tasks. A potential solution is to decrease the counter by 2+ every time a new task is added to the task set, cutting the number of tasks in half while maintaining encryption complexity.