The case of the 9 bit AES key
- We found that several PDF implementations generate their AES-256 file keys from state spaces small enough to enumerate.
- In MuPDF, only 9 bits of random state affect the actual AES-256 key.
- Other PDF editors like Foxit base their AES-256 key on time based randomness and thus also lead to keys that are trivial to recover.
Unverified
- We found that several PDF implementations generate their AES-256 file keys from state spaces small enough to enumerate.
- In MuPDF, only 9 bits of random state affect the actual AES-256 key.
- Other PDF editors like Foxit base their AES-256 key on time based randomness and thus also lead to keys that are trivial to recover.
Sources: V12