playfair_cipher_encrypt.py

# source : https://www.geeksforgeeks.org/playfair-cipher-with-examples/

# Python program to implement Playfair Cipher
 
# Function to convert the string to lowercase
 
 
def toLowerCase(text):
    return text.lower()
 
# Function to remove all spaces in a string
 
 
def removeSpaces(text):
    newText = ""
    for i in text:
        if i == " ":
            continue
        else:
            newText = newText + i
    return newText
 
# Function to group 2 elements of a string
# as a list element
 
 
def Diagraph(text):
    Diagraph = []
    group = 0
    for i in range(2, len(text), 2):
        Diagraph.append(text[group:i])
 
        group = i
    Diagraph.append(text[group:])
    return Diagraph
 
# Function to fill a letter in a string element
# If 2 letters in the same string matches
 
 
def FillerLetter(text):
    k = len(text)
    if k % 2 == 0:
        for i in range(0, k, 2):
            if text[i] == text[i+1]:
                new_word = text[0:i+1] + str('x') + text[i+1:]
                new_word = FillerLetter(new_word)
                break
            else:
                new_word = text
    else:
        for i in range(0, k-1, 2):
            if text[i] == text[i+1]:
                new_word = text[0:i+1] + str('x') + text[i+1:]
                new_word = FillerLetter(new_word)
                break
            else:
                new_word = text
    return new_word
 
 
list1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'k', 'l', 'm',
         'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
 
# Function to generate the 5x5 key square matrix
 
 
def generateKeyTable(word, list1):
    key_letters = []
    for i in word:
        if i not in key_letters:
            key_letters.append(i)
 
    compElements = []
    for i in key_letters:
        if i not in compElements:
            compElements.append(i)
    for i in list1:
        if i not in compElements:
            compElements.append(i)
 
    matrix = []
    while compElements != []:
        matrix.append(compElements[:5])
        compElements = compElements[5:]
 
    return matrix
 
 
def search(mat, element):
    for i in range(5):
        for j in range(5):
            if(mat[i][j] == element):
                return i, j
 
 
def encrypt_RowRule(matr, e1r, e1c, e2r, e2c):
    char1 = ''
    if e1c == 4:
        char1 = matr[e1r][0]
    else:
        char1 = matr[e1r][e1c+1]
 
    char2 = ''
    if e2c == 4:
        char2 = matr[e2r][0]
    else:
        char2 = matr[e2r][e2c+1]
 
    return char1, char2
 
 
def encrypt_ColumnRule(matr, e1r, e1c, e2r, e2c):
    char1 = ''
    if e1r == 4:
        char1 = matr[0][e1c]
    else:
        char1 = matr[e1r+1][e1c]
 
    char2 = ''
    if e2r == 4:
        char2 = matr[0][e2c]
    else:
        char2 = matr[e2r+1][e2c]
 
    return char1, char2
 
 
def encrypt_RectangleRule(matr, e1r, e1c, e2r, e2c):
    char1 = ''
    char1 = matr[e1r][e2c]
 
    char2 = ''
    char2 = matr[e2r][e1c]
 
    return char1, char2
 
 
def encryptByPlayfairCipher(Matrix, plainList):
    CipherText = []
    for i in range(0, len(plainList)):
        c1 = 0
        c2 = 0
        ele1_x, ele1_y = search(Matrix, plainList[i][0])
        ele2_x, ele2_y = search(Matrix, plainList[i][1])
 
        if ele1_x == ele2_x:
            c1, c2 = encrypt_RowRule(Matrix, ele1_x, ele1_y, ele2_x, ele2_y)
            # Get 2 letter cipherText
        elif ele1_y == ele2_y:
            c1, c2 = encrypt_ColumnRule(Matrix, ele1_x, ele1_y, ele2_x, ele2_y)
        else:
            c1, c2 = encrypt_RectangleRule(
                Matrix, ele1_x, ele1_y, ele2_x, ele2_y)
 
        cipher = c1 + c2
        CipherText.append(cipher)
    return CipherText


def final(key, text):
    key = toLowerCase(key)
    text = removeSpaces(toLowerCase(text))
    textList = Diagraph(FillerLetter(text))
    if len(textList[-1]) != 2:
        textList[-1] = textList[-1]+'z'
    Matrix = generateKeyTable(key, list1)

    CipherList = encryptByPlayfairCipher(Matrix, textList)
    CipherText = ""
    for i in CipherList:
        CipherText += i
    return CipherText