encryption - Password protect PDF documents on the fly without compromising the password -


i'm looking way password protect pdf files on fly without having store user's password in plaintext.

what generate user , owner keys according pdf specification , use encrypt document's strings , streams. there library out there supports functionality?

-- edit --

just clarify, want allow user enter password system once, time after able encrypt pdf file key generated password. pdf libraries require password passed in plaintext, want encryption function takes "public" key.

http://itextpdf.com/ has open source java , c# pdf libraries include encryption.


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