Device and method for generating a key

The invention relates to a device for generating a key, which device comprises a multimode interferometer that can be coupled to a light source and has a light path having an electro-optical material, the light path being designed in order to receive light on an input side, to influence the light under the influence of a locally varying refractive index of the electro-optical material, and in order to provide an influenced light to an output side. The device comprises a receiving unit, which is designed in order to receive the influenced light at the output side, and comprises an evaluation unit that is designed in order to carry out an evaluation based upon the influenced light, and in order to generate the key based upon the evaluation.