Good practice to use namespace or prefix to indicate what file function is from?

Good practice to use namespace or prefix to indicate what file function is
from?

For example, I have the function generate_salt() in encryption.file but
the person may not know where generate_salt() is from. Using a namespace
like encryption::generate_salt(), or encryption_generate_salt() for every
function in the encryption.file. Or would it be a waste of space and
typing because some IDEs can navigate you to the function?