I have found a small piece of code capable of encrypt (and decrypt) files in AES (128bit) CBC mode. It work flawlessy even in decryption so I belived that OpenSSL would be capable (of course) od decrypting my files but it seems impossibile. I get the "Error reading input files"
import os, random, struct
from Crypto.Cipher import AES
def encrypt_file(key, in_filename, out_filename=None, chunksize=64*1024):
""" Encrypts a file using AES (CBC mode) with the
16, 24 or 32 bytes long
Name of the input file
If None, '<in_filename>.enc' will be used.
Sets the size of the chunk which the function
uses to read and encrypt the file.
Chunksize must be divisible by 16.
if not out_filename:
out_filename = in_filename + '.enc'
iv = ''.join(chr(random.randint(0, 0xFF)) for i in range(16))
encryptor = AES.new(key, AES.MODE_CBC, iv)
filesize = os.path.getsize(in_filename)
with open(in_filename, 'rb') as infile:
with open(out_filename, 'wb') as outfile:
chunk = infile.read(chunksize)
if len(chunk) == 0:
elif len(chunk) % 16 != 0:
chunk += ' ' * (16 - len(chunk) % 16)
openssl aes-128-cbc -d -in test_enc.txt -out test_dec.txt
OpenSSL uses its own file format. In particular, there's a
Salted__ header, as well as a salt that's used to derive the IV (i.e. the IV is not directly stored with the encrypted data).
You can find some hints in https://scottlinux.com/2013/10/13/how-to-encrypt-a-file-with-openssl/ and in http://crypto.stackexchange.com/questions/3298/is-there-a-standard-for-openssl-interoperable-aes-encryption, but they don't describe the actual format.
You might be able to examine the OpenSSL code to figure that out, but the bottom line is that OpenSSL uses its own file format and you have to use it if you want OpenSSL to decrypt your files.