His main research goal is to protect private data in online applications against misuse. One way to achieve this goal is to hide the private data by means of encryption in such a way that without the authorization of the data owner, no one can see the content but still process the encrypted data for the required service. One simple example is to encrypt an image and ask the service provider if there is a face image of a suspect. Since the image is encrypted, there is no way of saying for the service provider. However, it is possible to determine this by running interactive, cryptographic protocols based on Homomorphic Encryption and Secure Multiparty Computation techniques.