Production-grade DP·FL: keeping data on-device is only the start — updates leak, so layer DP + secure aggregation
In one sentence DP (bound a single device's / user's influence on the model) + secure aggregation (the server sees only the sum of many devices' updates, not any single one). Real deployments FL ≠ private, watch local DP's ε, and don't mismatch user-level vs sample-level. This is the deployment face of Volume 3 DP fine-tuning at "federated + large-scale production."