Provable Synthetic Coordinates for Increasing PoWs Effectiveness against DoS and Spam

The effectiveness of synthetic coordinate systems against DoS and spam stems from the fact that, while changing or hiding a logical address is easier, changing the location of the spammer inside the network should be harder. But synthetic coordinate systems are limited by the fact that malicious nodes can easily lie about their position or introduce additional delays which have an immediate impact on it. For this purpose, we enhance the synthetic coordinate system provided by Vivaldi with secure nonces that are periodically broadcasted by trusted servers to achieve a provable location claim within the overlay network. As we advocate in this work, secure localization can help in choosing the hardness of PoWs since locations from which more malicious traffic originates can receive PoWs with higher difficulties.