Mar 27, 2023 · Mar 29, 2023
diff --git a/algorithms/cryptography/columnar_transposition_cipher.py b/algorithms/cryptography/columnar_transposition_cipher.py
 import math
 def encrypt(key, message):
    ciphertext = []
    for col in range(key):
        position = col
        while position < len(message):
            ciphertext.append(message[position])
            position += key
    return ''.join(ciphertext)

 def decrypt(key, message):
    numOfRows = math.ceil(len(message) / key)
    plaintext = []
    cipher = [*message]
    remainder = len(message)%key
    count=0
    if(remainder != 0):
        for i in range(0,len(message),numOfRows):
            count += 1
            if(count > remainder):
                cipher.insert(i+numOfRows-1,'#')
        cipher.append('#')
        for row in range(numOfRows):
            position = row
            while(position < len(cipher)):
                plaintext.append(cipher[position])
                position += numOfRows
        plaintext = [ele for ele in plaintext if ele != '#']
    else:
        for row in range(numOfRows):
            position = row
            while(position < len(message)):
                plaintext.append(message[position])
                position += numOfRows
    return ''.join(plaintext)
 def main():
    while(True):
        print("1. Encrypt")
        print("2. Decrypt")
        print("3. Exit")
        option = int(input("Enter the option: "))
        if(option == 1):
            text = input("Enter the plain text: ")
            k = int(input("Enter the key: "))
            cipher = encrypt(k,text)
            print("Ciphertext: ", cipher)
        if(option == 2):
            text = input("Enter the ciphertext: ")
            k = int(input("Enter the key: "))
            plain = decrypt(k, text)
            print("Plaintext: ", plain)
        if(option == 3):
            break
 main()
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,54 @@
		import math
		def encrypt(key, message):
		ciphertext = []
		for col in range(key):
		position = col
		while position < len(message):
		ciphertext.append(message[position])
		position += key
		return ''.join(ciphertext)

		def decrypt(key, message):
		numOfRows = math.ceil(len(message) / key)
		plaintext = []
		cipher = [*message]
		remainder = len(message)%key
		count=0
		if(remainder != 0):
		for i in range(0,len(message),numOfRows):
		count += 1
		if(count > remainder):
		cipher.insert(i+numOfRows-1,'#')
		cipher.append('#')
		for row in range(numOfRows):
		position = row
		while(position < len(cipher)):
		plaintext.append(cipher[position])
		position += numOfRows
		plaintext = [ele for ele in plaintext if ele != '#']
		else:
		for row in range(numOfRows):
		position = row
		while(position < len(message)):
		plaintext.append(message[position])
		position += numOfRows
		return ''.join(plaintext)
		def main():
		while(True):
		print("1. Encrypt")
		print("2. Decrypt")
		print("3. Exit")
		option = int(input("Enter the option: "))
		if(option == 1):
		text = input("Enter the plain text: ")
		k = int(input("Enter the key: "))
		cipher = encrypt(k,text)
		print("Ciphertext: ", cipher)
		if(option == 2):
		text = input("Enter the ciphertext: ")
		k = int(input("Enter the key: "))
		plain = decrypt(k, text)
		print("Plaintext: ", plain)
		if(option == 3):
		break
		main()