PdfStamper类的setEncryption方法中使用哪种加密算法/方法？

Question

I am referring to following method here. ( Link for more details)

public void setEncryption(boolean strength,
                          String userPassword,
                          String ownerPassword,
                          int permissions)
                   throws DocumentException

Which encryption algorithm/method/standard is being used internally by itext to encrypt the pdf?

Is it AES?

Answer 1

The Javadocs for a closely related interface, PdfEncryptionSettings , provides some clues:

Encryption settings are described in section 3.5 (more specifically section 3.5.2) of the PDF Reference 1.7. They are explained in section 3.3.3 of the book 'iText in Action'.

Looking at that section of the reference we can see that either RC4 or AES is used.

With that in mind, I'd say the specific method you linked to will either do 40-bit RC4 or 128-bit RC4. An overloaded alternative method allows you to specify 40-bit RC4, 128-bit RC4 or 128-bit AES.