The application relates to a method for aggregation of a performance indicator of a device including: concatenating a respective first data item to a plurality of second data items in the device; encrypting the plurality of concatenated second data items relevant for computing the performance indicator using a first encryption key in the device, wherein the first encryption key is based on an additive homomorphic encryption scheme; sending the encrypted concatenated second data items to a computation cluster; computing the performance indicator on the computation cluster using the encrypted concatenated second data items and computing an aggregate value regarding the performance indicator by summing up the encrypted concatenated second data items; sending the aggregate value to a server of a service provider of the device; decrypting the aggregate value using a second encryption key on the server of the service provider; and verifying the decrypted result by checking whether the decrypted sum computed by summing up the encrypted concatenated second data items comprises a predetermined value. The present application also relates to a corresponding system and corresponding computer program product including one or more computer readable media having computer executable instructions for performing the steps of the method.