Vcipher1

# A polyalphabetic (Vigenere) cipher encryption and decryption program
# Based on a single keyword and a modified alphabet
# messages to be encrypted must be lower case letters only and not contain spaces,
# numbers, punctuation, or symbols

# variables
alphabet0 = "kryptosabcdefghijlmnquvwxz"# The alphabet variant
keyWord = ""
plainText = ""
alphaLength = len(alphabet0)

# functions
# Set up the alphabet grid
def matAlpha(m, n):
    global gridAlpha
    gridAlpha = []  # define empty matrix
    # n rows
    # m cols
    for i in range(n):  # total row is n
        row = []
        for j in range(m):  # total column is m
            row.append("")  # adding "" null string for each column for this row
        gridAlpha.append(row)  # add fully defined column into the row

# Fill alphabet grid with 26 shifted alphabets
def FillAlpha(aL):
    global gridAlpha
    stoLine = 0
    for alphab in range(aL):
        for letter in range(aL):
            gridAlpha[alphab][letter] = alphabet0[((letter + alphab)%aL)]

def Encrypt():
    global gridAlpha, plainText, keyWord, alphabet0, cryptOut
    plainText = input('Enter the message: ')
    keyWord = input('Enter the keyword: ')
    # variables for Encyption
    cryptOut = ""
    crypText = []
    textLength = len(plainText)
    keyLength = len(keyWord)
    # loop through the plain text and encrypt
    for x in range(textLength):
        letterX = plainText[x]
        keyNum = x%keyLength
        keyLetter = keyWord[keyNum]
        alphaNum = alphabet0.find(keyLetter)
        letterNum = alphabet0.find(letterX)
        cryptLetter = gridAlpha[alphaNum][letterNum]
        crypText.append(cryptLetter)

    cryptLength = len(crypText)
    for y in range(cryptLength):
        cryptOut += crypText[y]

    print(cryptOut) #print the ciphertext
    # save as a text file
    text_file = open("cryptOut.txt", "w")
    n = text_file.write(cryptOut)
    text_file.close()

def Decrypt():
    global gridAlpha, keyWord, alphabet0, cryptIn, plainOut
    cryptIn = input('Enter the ciphertext: ')
    keyWord = input('Enter the keyword: ')
    # variables for decryption
    plainOut = ""
    plainText = []
    cryptLength = len(cryptIn)
    keyLength = len(keyWord)
    # loop through the plain text and encrypt
    for x in range(cryptLength):
        letterX = cryptIn[x]
        keyNum = x%keyLength
        keyLetter = keyWord[keyNum]
        alphaNum = alphabet0.find(keyLetter)
        letterNum = gridAlpha[alphaNum].index(letterX)
        plainLetter = alphabet0[letterNum]
        plainText.append(plainLetter)
    plainLength = len(plainText)
    for y in range(plainLength):
        plainOut += plainText[y]

    print(plainOut) #print the plaintext

def DecryptFile():
    global gridAlpha, keyWord, alphabet0, cryptIn, plainOut
    getCryptext()
    keyWord = input('Enter the keyword: ')
    # variables for decryption
    plainOut = ""
    plainText = []
    cryptLength = len(cryptIn)
    keyLength = len(keyWord)
    # loop through the plain text and encrypt
    for x in range(cryptLength):
        letterX = cryptIn[x]
        keyNum = x%keyLength
        keyLetter = keyWord[keyNum]
        alphaNum = alphabet0.find(keyLetter)
        letterNum = gridAlpha[alphaNum].index(letterX)
        plainLetter = alphabet0[letterNum]
        plainText.append(plainLetter)
    plainLength = len(plainText)
    for y in range(plainLength):
        plainOut += plainText[y]

    print(plainOut) #print the plaintext

def getCryptext():
    global cryptIn
    with open('cryptOut.txt', 'r') as file:
        crypt = file.read().rstrip()
        cryptIn = crypt.casefold()


#example using alphabet0 = kryptosabcdefghijlmnquvwxz and keyword = palimpsest
# message
#betweensubtleshadingandtheabsenceoflightliesthenuanceofiqlusion
# resulting ciphertext
#emufphzlrfaxyusdjkzldkrnshgnfivjyqtquxqbqvyuvlltrevjyqtmkyrdmfd

#main section
matAlpha(alphaLength, alphaLength)
FillAlpha(alphaLength)

#inputs
action = input("Enter e to encrypt a message, d to decode a ciphertext, f to decode a .txt file: ")
if action == "e":
    Encrypt()
elif action == "d":
    Decrypt()
elif action == "f":
    DecryptFile()
else:
    print("Action invalid")