import pyDes, sys

# For Python3, you'll need to use bytes, i.e.:
#   data = b"Please encrypt my data"
#   k = pyDes.des(b"DESCRYPT", pyDes.CBC, b"\0\0\0\0\0\0\0\0", pad=None, padmode=pyDes.PAD_PKCS5)

def plaintext_from_file():
	f = open("input-des.txt", "r")
	content = f.read()
	f.close()
	print("Plaintext:", content)
	return content

def key_from_file():
	f = open("key-des.txt", "r")
	content = f.read()
	f.close()
	if len(content) != 8:
		print("Default key: 12345678 (has to be a multiple of 8 bytes)")
		return "12345678"
	print("Key:",content)
	return content

def ciphertext_to_file(content):
	f = open("cipher-des.txt", "w")
	f.write(str(content))
	f.close()

def ciphertext_from_file():
	f = open("cipher-des.txt", "r")
	content = f.read()
	f.close()
	return content

def plaintext_to_file(content):
	f = open("plain-des.txt", "w")
	f.write(str(content))
	f.close()

if len(sys.argv) != 2:
	print("Usage: python CipherDES.py <e> or <d>")
	exit()
else:
	data = str.encode(plaintext_from_file())
	key = str.encode(key_from_file())
	k = pyDes.des(key, pyDes.CBC, b"\0\0\0\0\0\0\0\0", pad=None, padmode=pyDes.PAD_PKCS5)
	d = k.encrypt(data)

	if sys.argv[1] == "e":
		d = k.encrypt(data)
		ciphertext_to_file(d)
		print ("Encrypted:", d)

	elif sys.argv[1] == "d":
		plaintext_to_file(k.decrypt(d))
		print ("Decrypted:", k.decrypt(d))

	else:
		print("Usage: <e> for encryption or <d> for decryption")
		exit()