Grimen, GisleMönch, ChristianMidtstraum, RogerKaragiannis, DimitrisMayr, Heinrich C.2019-08-122019-08-1220063-88579-178-1https://dl.gi.de/handle/20.500.12116/24193We describe a new purely software-based, self-checking mechanism designed to prevent tampering of client programs in client/server-applications like online-games, peer-to-peer networks, or online auction systems. Our mechanism consists of randomly creating checksum algorithms at the server. The checksum algorithms are integrated into autonomous short-lived software code, called Mobile Guards, which are downloaded to a client program during its execution. The client programs are designed to be functionally dependent on the execution of a Mobile Guard. The randomly created checksum functions and the concept of Mobile Guards enable a highly dynamic protection mechanism, capable of rapidly evolving as new threats arise.enText/Conference Paper1617-5468