This is because the encryption of this CAJ paper cannot be copied and opened. What should I verify when I open it, such as my IP address or the physical address of my computer when I download it?

I met the same situation. In a university campus network, files downloaded from my notebook can be opened in my notebook, but they cannot be printed and saved, that is, they are encrypted.

The key is that files cannot be copied. If you copy it on another computer, it won't open. The following prompt appears.

So it can only be opened on the computer that downloaded the literature at that time. At present, many colleges and universities have high requirements on the confidentiality and copyright of papers, and only teachers and students in this school can read them.