Source code

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# 2020/01/20
# ZChaCha20FileBatchCipher.py

import traceback

from SOL4Py.crypto.ZChaCha20Cipher import *

class ZChaCha20FileBatchCipher(ZChaCha20Cipher):

    # encrpted file format: nonce + real_encrypted_data

    # The constructor
    def __init__(self):
        super().__init__()

    # This method will read a file into a memory in a lump, and encrypt the read data by key and nonce, 
    # and save it to another file.
    # key may be created by Random.get_random_bytes(self.KEY_SIZE)  #32
    # nonce is generated automatically in this method, and embedded to the 
    # ecnrypted file as something like this: nonce + payload
    def encrypt(self, in_filename, out_filename, key):
        #This is a very simple method, but not suitable for a large file
        with open(in_filename, "rb" ) as infile:
            data = infile.read()
        # Generate nonce 
        nonce = self.generate_nonce()
        encrypted = super().encrypt(data, key, nonce)
        nonce_encrypted = nonce + encrypted
        with open(out_filename, "wb" ) as outfile:
            outfile.write(nonce_encrypted)
      
 
    # This method will read a file into a memory in a lump, and decrypt the read data by key and nonce, 
    # and save it to another file.
    #
    def decrypt(self, in_filename, out_filename, key):
        #This is a very simple method, but not suitable for a large file
        with open(in_filename, "rb") as infile:
            encrypted = infile.read()

        # Extract iv from the encrpted bytes.
        nonce = encrypted[:self.NONCE_SIZE]
        # Extract payload from the encrypted
        encrypted = encrypted[self.NONCE_SIZE:]
        
        decrypted = super().decrypt(encrypted, key, nonce)

        with open(out_filename, "wb") as outfile:
            outfile.write(decrypted)