Media Server File Decryption

Overview

Example script to decrypt a file downloaded from Acrobits Media Server.

Python Example

#!/usr/bin/python3

from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
from binascii import unhexlify,crc32

key = unhexlify('F4EC56A83CDA65B2C6DC11E2CF693DAA')
nonce = b'\0'*len(key)

cipher = Cipher(algorithms.AES(key), modes.CTR(nonce), backend=default_backend())
dec = cipher.decryptor()

file_in = open('encrypted', 'rb')
file_out = open('decrypted.jpg', 'wb')

crc = 0

while True:
  enc_block=file_in.read(10240)
  if not enc_block:
     break
  print('.', end='')
  dec_block = dec.update(enc_block)
  crc = crc32(dec_block, crc)
  file_out.write(dec_block)

print()

file_in.close()
file_out.close()

print("Hash: "+str(crc))

OpenSSL Example

openssl enc -aes-128-ctr  -d  -K F4EC56A83CDA65B2C6DC11E2CF693DAA  -iv 00000000000000000000000000000000 -nopad -in encrypted -out decrypted_file.jpg

crc32 decrypted_file.jpg

The encrypted version is available here.

The decrypted version is available here.

The hex-encoded key for this file is F4EC56A83CDA65B2C6DC11E2CF693DAA

The unsigned decimal integer hash of the original is 4488649