caesar_in_progress.py

"""
Author: Rafeh Qazi
Program: Encryption and Decryption
Resource: http://www.practicalcryptography.com/ciphers/caesar-cipher/
"""

# Use whatever key as long as it is consistent.
KEY = 17


def read_file(file_name):
    """Read a file and return a list of lines."""

    with open(file_name, 'r') as f:
        return f.readlines()


def caesar_cipher(letter, key=12):
    """Letter in the first 256 ascii is shifted 'key' positions. Default key is 12."""

    # mod 256 to create a world of [0,255] integers.
    return (ord(letter) + key) % 256

def caesar_encryption(file_name, key=12):
    file_stuff = read_file(file_name)
    print(file_stuff)
    gibberish = [caesar_cipher(char) for elem in file_stuff for char in elem]
    print(gibberish)


def caesar_decryption(encrypted_letter, key=12):
    """Used to reverse the destruction caused by caesar_encryption. Default key is 12."""

    return chr((encrypted_letter - key) % 256)


# decrypt(encrypt(x)) should give you back x.
assert caesar_decryption(caesar_cipher('e', 20), 20) == 'e'

if __name__ == '__main__':
    caesar_encryption('scratch_1.txt')
    print('------')

    encrypted_message = []
    for letter in 'bananas':
        encrypted_message.append(caesar_cipher(letter, KEY))

    print(encrypted_message)

    decrypted_message = []
    for encrypted_letter in encrypted_message:
        decrypted_message.append(caesar_decryption(encrypted_letter, KEY))

    print(''.join(decrypted_message))