import pyDes

def encrypt_file(filename, key, iv):

with open(filename, 'rb') as f:

plaintext = f.read()

k = pyDes.des(key, pyDes.CBC, iv, pad=None, padmode=pyDes.PAD_PKCS5)

ciphertext = k.encrypt(plaintext)

with open(filename + ".enc", 'wb') as f:

f.write(ciphertext)

def decrypt_file(filename, key, iv):

with open(filename, 'rb') as f:

ciphertext = f.read()

k = pyDes.des(key, pyDes.CBC, iv, pad=None, padmode=pyDes.PAD_PKCS5)

plaintext = k.decrypt(ciphertext)

with open(filename[:-4], 'wb') as f:

f.write(plaintext)

key = b"DESKEY--"

iv = b"\0\0\0\0\0\0\0\0"

encrypt_file("test.txt", key, iv)

decrypt_file("test.txt.enc", key, iv)