Dynamic Multi-Threshold Metering Schemes

A metering scheme is a method by which an audit agency is able to measure the interaction between clients and servers on the web during a certain number of time frames. Naor and Pinkas [7] considered metering schemes in which any server is able to construct a proof to be sent to the audit agency if and only if it has been visited by at least a number, say h, of clients in a given time frame. In their schemes the parameter h is fixed and is the same for any server and any time frame. This is acceptable whenever there is a long-term relationship between the audit agency and the servers. In order to measure any number of visits in any granularity we introduce dynamic multi-- threshold metering schemes, which are metering schemes in which there is a threshold h t j associated to any server S j for any time frame t. We mainly focus on the efficiency of dynamic multi--threshold metering schemes, providing lower bounds on the size of the information distributed to clients and to servers (th..

On Metering Schemes

In order to decide on advertisement fees for web servers, Naor and Pinkas introduced (threshold) metering schemes secure against coalitions of corrupt servers and clients. Several researchers have generalized the idea of Naor and Pinkas: first metering scheme with pricing and dynamic multi-threshold metering schemes have been proposed; later the solution has been extended to allow general access structures and an approach on linear algebra has been introduced. But all previous papers consider the following scenario-a general (or threshold) access structure for the clients and a threshold access structure for the servers. We generalize the model allowing also a general access structure for the servers, moreover we strengthen it limiting the possibility of corrupt servers to help each other. A more efficient protocol satisfying the requirements of the new model is described. Naor and Pinkas show that one should be able also to detect illegal behavior of clients, i.e., one needs to verify the shares received from clients. Most metering schemes do not offer this feature. But Ogata and Kurosawa pointed out a minor flaw in the extension protocol by Naor and Pinkas providing detection of such illegal behavior and propose a correction. So, we extend the used linear algebra approach in order to build robust unconditionally secure general metering schemes. As a tool to achieve this goal we introduce doubly-labelled matrices and an operation on such matrices. Certain properties of this operation are proven.