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AES_128_CTR encryption with openssl and PyCrypto

Learning the correct way to convert AES_128_CTR encryption using openssl to PyCrypto.

Firstly, I made encryption through openssl as follows:

openssl enc -aes-128-ctr -in input.mp4 -out output.openssl.mp4 -K 7842f0a1ebc38f44e3e0c81943f68582 -iv d01f40dfc8ec8cd9

And then I tried to do the same through PyCrypto:

from Crypto.Cipher import AES
from Crypto.Util import Counter
key = '7842f0a1ebc38f44e3e0c81943f68582'
iv = 'd01f40dfc8ec8cd9'

ctr_e = Counter.new(128, initial_value=int(iv, 16))
encryptor = AES.new(key.decode('hex'), AES.MODE_CTR, counter=ctr_e)

with open('output.pycrypto.mp4', 'wb') as fout:
    with open('input.mp4', 'rb') as fin:
        fout.write(encryptor.encrypt(fin.read()))

I assume they should be similar, but this is not the case:

diff output.openssl.mp4 output.pycrypto.mp4
Binary files output.openssl.mp4 and output.pycrypto.mp4 differ
+4
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1 answer

OpenSSL , ( , ) IV . , 16- . IV , .

, Python, Counter, :

  • 64 128 , 8 ; , , , , ( 64 , )
  • 1, CTR 0; , , " " .

, :

from Crypto.Cipher import AES
from Crypto.Util import Counter

key = '7842f0a1ebc38f44e3e0c81943f68582'.decode('hex')
iv = 'd01f40dfc8ec8cd9'.decode('hex')

ctr_e = Counter.new(64, prefix=iv, initial_value=0)
encryptor = AES.new(key, AES.MODE_CTR, counter=ctr_e)

with open('output.pycrypto.mp4', 'wb') as fout:
    with open('input.mp4', 'rb') as fin:
        fout.write(encryptor.encrypt(fin.read()))
+4

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