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+Frequently Asked Questions
+==========================
+
+Why Don't You Support Writing a PDF File with Encryption?
+---------------------------------------------------------
+
+PDF encryption offers very little protection:
+
+- PDF encryption keys are reused and derived from the user password (padded
+  with a standard base string) and the object numbers in the file.
+- RC4 encryption (40- and 128-bit) was broken years ago.
+- AES encryption (128- and 256-bit) is better, but PDF uses Cipher Block
+  Chaining (CBC) which enables attacks that allow the original encryption key
+  to be recovered.
+
+In addition, PDF usage controls (no print, no copy, etc.) are tied to this
+encryption, making them trivial to bypass.