I have a bash script that reads data from a data file and does some processing, due to security reasons, I have to encrypt my data file, how can my bash script handle this?

I mean how can my bash script read data from a encrypted file without me having to type the Key for my file?

any sort of help is greatly appreciated.

What if you hardcode the key inside the script and then encrypt the script itself? Given that shell script itself is not human readable anymore, your key is safe.
Downside is that every change in script would need to you to re-encrypt it.