IPFS Storage Management

In a project where we use IPFS, I need to send files encrypted. In this case, it keeps generating a new CID for me constantly. How can I prevent this?

Normally, after uploading a file, if I update the file, it should take the new part and show the whole file. However, in an encrypted file, how will it check the file integrity? What can I do in this case? Can you help me?