PM for Container Apps here. Communication between your app and the dapr sidecar occurs over localhost because the two containers (your app, and the sidecar) are hosted together in an underlying Kubernetes pod. In terms of mTLS, if you make use of the service invocation API, you will get sidecar-to-sidecar encryption automatically. This communication between sidecars happens over gRPC. We manage the encryption as part of the platform, so no additional work is required on your side. Let me know if you have additional questions