Is it possible to look at a PDF and tell what encryption level was use to encrypt it? We are proposing to set an AES encryption level, in Word by group policy, and wanted to confirm this was actually used on the resultant document. The default AES used in word is 128 which we wanted to increase to 256. Thanks for any ideas on how to test this.
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What do you mean by *look at*? – mkl Feb 27 '13 at 11:00
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With AES it is impossible to inspect encrypted data and determine the key length used to encrypt it. AES has a constant block size for all key sizes, so you will merely see n x 16 bytes of apparently random data.
Duncan Jones
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Pity, thanks though. I suppose we will just have to trust the policy is correctly applied – user75163 Feb 27 '13 at 15:20
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@user75163 It's plausible Microsoft embeds metadata in the output to indicate which key was used, but good luck trying to find that or read it! :-) – Duncan Jones Feb 27 '13 at 15:36