Abstract: The invention relates to an apparatus for checking the integrity of sensor-data streams (15) with a detection unit (1) having a sensor-data input. In order that individual sensor-data stream sections (11, 12, 13, 14) of a sensor-data stream (15) can also be checked for integrity independently of further processing in existing infrastructures (26), in particular in the case of transmission across a plurality of infrastructure nodes, with low resource consumption, it is proposed in that the detection unit (1) comprises a control device (4), connected to the sensor-data input and to a hash tree memory (5), for calculating and storing hash values on the basis of individual sensor-data stream sections (11, 12, 13, 14) and on the basis of subordinate hash values of the hash tree, and in that the control device (4) has a root hash output (19) for outputting the most recently calculated root hash value.