Quantum key distribution and Denial-of-Service: Using strengthened classical cryptography as a fallback option

Within quantum networks (employing quantum key distribution - QKD), the attacker has no chance to get hold of the established keys (most commonly used as one time pads) without being detected by the communicating parties. So the attacker might change his strategy to denial of service in order to inhibit the efficient usage of the quantum-key-distribution-links and one-time-pad-encryption and hence to force the use of classical (a)symmetric cryptography. In this paper we will propose a method for strengthening classical cryptographic algorithms by the use of small amounts of one time pads, so that these algorithms can be used for an emergency operation when suffering a Denial-of-Service attack and during the time needed to fix it. Additional scenarios of using the presented approach include the down time of QKD-links or QKD-devices in case of failure or maintenance.