Mastering Python for Networking and Security

File decryption with AES

For decrypting, we need to reverse the preceding process to decrypt the file using AES.

You can find the following code in the aes-file-decrypt.py file inside the pycrypto folder:

from Crypto.Cipher import AESfrom Crypto.Hash import SHA256import os, random, structdef decrypt_file(key, filename):    chunk_size = 64*1024    output_filename = os.path.splitext(filename)[0]    #open the encrypted file and read the file size and the initialization vector.     #The IV is required for creating the cipher.    with open(filename, 'rb') as infile:        origsize = struct.unpack('<Q', infile.read(struct.calcsize('Q')))[0]        iv = infile.read(16)        #create the cipher using the key and the IV.        decryptor = AES.new(key, AES.MODE_CBC, iv) #We also write the ...