The QlikView file is not encrypted. It is just binary code slightly scrambled so that you cannot read the clear text. But there is in principle no security. If someone gets hold of a file with sensitive data, I would guess it is fairly straightforward to extract what you want.
If you want a secure solution, you should keep the file on a server and connect to it using e.g. SSL.
It depends on what you mean with "empty the connection string".
If you change the connection string to a dummy user (with the right to see only non-sensitive data) then it could work: Running the script will discard old data, and replace it with new non-sensitive data, and you can then distribute the file.