By processing aggregated data in a trusted environment, a system can reduce opportunities for tampering with aggregated data that is processed in a peer-to-peer chain. Each device may pass the predecessor aggregated data to a trusted environment in that device, which obtains local data for that device and aggregates it with the predecessor aggregated data, producing an output aggregated data. Optionally, the system can identify when a device has previously processed the aggregated data, reducing the possibility that the device can be used to aggregate data repeatedly. The aggregated data may be digitally signed or encrypted to enhance the tamper resistance of the data payload.