transpositional

# Transposition Cipher Encryption
# http://inventwithpython.com/hacking (BSD Licensed)
import math
global ciphertext
def main():

    myMessage = input("Enter a message to encrypt")
    myKey = int(input("Choose a key"))

    ciphertext = encryptMessage(myKey, myMessage)

    # Print the encrypted string in ciphertext to the screen, with
    # a | (called "pipe" character) after it in case there are spaces at
    # the end of the encrypted message.
    print(ciphertext + '|')
    decrypt(ciphertext)
    # Copy the encrypted string in ciphertext to the clipboard.



def encryptMessage(key, message):
    # Each string in ciphertext represents a column in the grid.
    ciphertext = [''] * key

    # Loop through each column in ciphertext.
    for col in range(key):
        pointer = col

        # Keep looping until pointer goes past the length of the message.
        while pointer < len(message):
            # Place the character at pointer in message at the end of the
            # current column in the ciphertext list.
            ciphertext[col] += message[pointer]

            # move pointer over
            pointer += key

    # Convert the ciphertext list into a single string value and return it.
    return ''.join(ciphertext)


def decrypt(ciphertext):
    myKey = 1
    for x in range (100):
        plaintext = decryptMessage(myKey, ciphertext)
        myKey+=1
        print(plaintext + '|')

def decryptMessage(key, message):
    # The transposition decrypt function will simulate the "columns" and
    # "rows" of the grid that the plaintext is written on by using a list
    # of strings. First, we need to calculate a few values.

    # The number of "columns" in our transposition grid:
    numOfColumns = math.ceil(len(message) / key)
    # The number of "rows" in our grid will need:
    numOfRows = key
    # The number of "shaded boxes" in the last "column" of the grid:
    numOfShadedBoxes = (numOfColumns * numOfRows) - len(message)

    # Each string in plaintext represents a column in the grid.
    plaintext = [''] * numOfColumns

    # The col and row variables point to where in the grid the next
    # character in the encrypted message will go.
    col = 0
    row = 0

    for symbol in message:
        plaintext[col] += symbol
        col += 1 # point to next column

        # If there are no more columns OR we're at a shaded box, go back to
        # the first column and the next row.
        if (col == numOfColumns) or (col == numOfColumns - 1 and row >= numOfRows - numOfShadedBoxes):
            col = 0
            row += 1

    return ''.join(plaintext)

# If transpositionEncrypt.py is run (instead of imported as a module) call
# the main() function.
if __name__ == '__main__':
    main()