Decrypt Message Center payload

Our client wants to send a Message Center rtEvent payload with encrypted data. We are already using https/SSL but to protect personal information encryption is recommended. How do we go about decrypting payload using the MC Events? And since the ask is for a Real/Near Real-time targeting, we can't decrypt in a workflow before passing the data to delivery.

Once again we appreciate all the contributors here @61380 Experience League for helping folks like us who are trying to gain more knowledge about these tools. So Thank you!!

Rajiv