Can I create different private keys to read same form's data?

Not just one private key that's shared between users, but a private key per user that can open the same form.

According to the purpose of this feature users with sub accounts should not use this feature, or you can share your private key with sub users to be able to access submissions. Just to be clear, there is only one private key for each form and the form owner can share it to let others access form submissions. You can't create different private keys more than one for a specific form.

Also, you can find detailed information about encrypted forms in this blog post.

If you need further assistance please ask away.