Hello Ruban,
I understand that you would like to verify for yourself that the connection between the Cloud SQL Proxy and your Cloud SQL instance is secure. Security is high on the list of many people these days and asking questions about it is a good habit.
I reached out to the Networking Specialists to provide some details about what you’re looking for and was able to get some information that I’d like to share with you.
I looked at your question and saw that you are using a local machine. If the local machine, which I assume is a Compute Virtual Machine, the encryption is handled by default GCP encryption because it is within the Google Cloud. This level of encryption cannot be observed. This is the case from Google Cloud to the Cloud SQL proxy.
The part from the Cloud SQL Proxy to the Cloud SQL instance is taken care of by a built-in feature of Cloud SQL Proxy.
I hope this helps and if you have further questions, please reply.