Cipher App

This is a simple cipher web application that features:

• Caesar Cipher
• Base64 Encoding/Decoding

This is done using flask and python, with a simple html frontend and a Caesar Cipher python script.

Usage

# Install the requirements
pip install -r requirements.txt

# Run the app
python app.py

File Locations

All current and future cipher files will be located in the Ciphers folder.

Web application files are located in root directory.

Caesar Cipher

The Caesar Cipher is a simple cipher that shifts the alphabet by a certain amount. For example, if the shift is 3, then A becomes D, B becomes E, and so on. This is done by using the ord() and chr() functions in python.

What's different about this Caesar Cipher portion is the ability to include a One Time Pad (OTP) in the form of a CSV or TXT file. This fortifies the cipher by adding a predefined shift to the characters. The OTP looks like this:

19 33 71 15 21 25 43 38 9 68 2 79 85 97 62 80 63 61 5 71 97 73 47 20 5 6 11 83 3 97 61 11 92 67 11 59 9 53 97 39 94 63 4 99 16 3 43 42 93 28 41 18 72 75 92 16 66 82 77 10 36 1 40 73 78 11 90 94 31 70 52 52 80 45 15 60 70 6 47 29 36 28 4 90 92 8 36 56 63 85 37 81 82 35 62 20 41 41 79 68 

Where each number is a shift value for each character in the message.

The OTP will be generated and saved into both a CSV and TXT file if use_pad is set to True but no file_name or file is provided. This is done with secrets instead of random to ensure that the OTP is cryptographically secure.

Read more about secrets here

Usage of Caesar Cipher class

# Import the class
from collections import deque

text = "Hello World, this is a test!"

# Pad Declaration using a list in a deque
pad = deque([19, 33, 71, 15, 21, 25, 43, 38, 9, 68, 2, 79, 85])

cipher = CaesarCipher(40, use_pad=False)
enc = cipher.encrypt(text)

decipher = CaesarCipher(40, use_pad=False)
dec = decipher.decrypt(enc)

cipher2 = CaesarCipher(40, use_pad=True, file_name='./pad.txt')
enc = cipher.encrypt(text)

decipher2 = CaesarCipher(40, use_pad=True, file_name='./pad.txt')
dec = decipher.decrypt(enc)

The Constructor allows for multiple parameters:

• shift - The shift value for the cipher (Default in the Web Application is 3, no default in the class)
• pad - deque object containing the OTP (Default is None)
• file_name - The name of the file containing the OTP (Default is None)
• file - The file containing the OTP (Default is None)
• use_pad - Whether to use the OTP (Default is False)

Above is the sample usage of the class. The object will have to be recreated for each message to be encrypted/decrypted since the OTP is a one time use.

Base64 Encoding/Decoding

Base64 is a way to encode binary data into a string format. This is done by splitting the binary data into 6-bit chunks and then converting each chunk into a character. This is done by using the base64 module in python.

The base64 encoding/decoding is done using the base64 module in the web application.

Web Application

The web application is done using flask and python. The frontend is done using html and css.

This is a simple web application that allows the user to encrypt/decrypt messages using the Caesar Cipher and Base64 Encoding/Decoding.

Basic Functions:

• Fields are automatically updated as the user types in the message.
• The user can choose to use the OTP (via a file upload)
• Sliders can be used to change the shift value for the Caesar Cipher
• Both the Caesar Cipher and Base64 Encoding/Decoding can be used at the same time

Launching the Web Application

To launch the web application, run the app.py file. This will launch the web application on localhost:5000.

python app.py

Ensure that the requirements in requirements.txt file is installed before running the application.