Which binary bits tells the file is password protected zip or rar file?

Question

I am looking for the bit flags to detect the file is password-protected, not a regular .zip or .rar.

Answer 1

You can use zipinfo and unrar to test whether a ZIP file is encrypted. E.g.:

zipinfo -v file.zip |grep 'file security status:\s*encrypted'
unrar v -p- file.rar 2>&1|grep 'Encrypted file'

Answer 2

You can read about the header structure of rar here

And about the zip header structure here

It helps to download the source code of opensource unpackers to read some code examples.