Wireless Sensor Networks (WSNs) are networks of many small sensor node devices that frequently measure real-world phenomena. Those sensor nodes offer only restricted resources regarding processing power and storage, but yet WSNs have the potential to produce large amounts of data. In order to to unburden the operators of WSNs, we investigate to what extend cloud computing can be utilized to allow the WSN operators to outsource the storage and processing of sensor data. However, cloud computing is subject to severe security concerns as users of the cloud lose control over their potentially sensitive data. To this end, we develop a security architecture for the secure storage and processing of sensor data in the cloud. We introduce a special device, the Trust Point, to ensure the transport security and object security of sensor data within the control of the WSN operator. We enable the WSN operator to selectively authorize trusted cloud services to process sensor data on his behalf. Hence, we achieve to outsource sensor data in a secure and user-controllable way. Our evaluation shows that our framework has the potential to be realized with resource-constrained and thus energy-efficient Trust Point devices.