Method to transmit data in an ad hoc network or a sensor network with the network comprising a multitude of sensor nodes to sensor data, at least one aggregator node to aggregate the sensored data of at least a subset of the sensor nodes, and at least one sink node to collect the data of the aggregator node is characterized in--regarding a high level of security against attacks from outside while transmitting data, and regarding an economic energy consumption--that the sensored data is encrypted at the sensor nodes, that the encrypted data is transmitted to one of the aggregator nodes, that at the aggregator node an aggregation function is executed on the encrypted data, and that the result of the aggregation function is transmitted to the sink node and decrypted there.