IV must be 16 bytes long

[pzelchenko]

I have no idea if this is an old or obsolete issue - I just came into the de-DRM discussion through some Web searches [1a, 1b], not directly through ApprenticeAlf. I attempted using per the descriptions:

ineptkey_v5.4.pyw
ineptpdf_v7.10.pyw

Got the error you see in the title ("IV must be 16 bytes long") and tried adding the following code (via [2]) at line 113 of ineptkey_v5.4.pyw, at the invocation of the new AES instance forced a 16-byte key:

iv = os.urandom(16)
self._aes = _AES.new(key, _AES.MODE_CBC, iv)

This allowed a proper decryption of a DRM-encrypted PDF. Again, I don't know if this is an obsolete issue, but we have to pay attention to the many old threads online that don't connect to Github directly. A large number of people (most?) attempting to remove DRM today will go to these top hits in Google and hit a dead end after trying ineptkey and failing.

[1a] http://amrhaps.net/english/post/2011/06/05/Adobe-Digital-Editions-Ubuntu-and-DRMs
[1b] https://epubor.com/ineptpdf-pyw.html
[2] https://stackoverflow.com/questions/36834580/iv-must-be-16-bytes-long-error-in-aes-encryption

[ElleKayEm]

Those are pretty old. Current scripts here are adobekey.py 7.0 and ineptpdf.py 9.0.0.