Fig. 1: System Model and FAMHE workflow.

All entities are interconnected (dashed lines) and communication links at each step are shown by thick arrows. All entities (data providers (DPs) and querier) are honest but curious and do not trust each other. In 1. the querier sends the query (in clear) to all the DPs who (2.) locally compute on their cleartext data and encrypt their results with the collective public key. In 3. the DPs' encrypted local results are aggregated. For iterative tasks, this process is repeated (Iterate). In 4. the final result is then collectively switched by the DPs from the collective public key to the public key of the querier. In 5. the querier decrypts the final result.