A security unit which is suitable for a device, in particular an IOT device, for running one or more applications for a secure data exchange with one or more servers which provide web services is provided. The security unit is designed with the following:—means for imaging original data onto corresponding replacement data and/or vice versa, wherein the original and/or replacement data forms a respective original and/or replacement key and/or can be used to form same—means for detecting a replacement key which is supplied by an application being ran and which corresponds to an original key, and—means for providing a required original key which corresponds to the replacement key using the imaging means in order to allow the original key to be used for the secure data exchange with the server.