Distributed Filtering with Contags and Security-Labels

accessed through and transmitted over these interconThis contribution presents a new access control method based on distributed filtering of data packets at network boundaries. It addresses well-known security problems that occur at network interconnection points. Our method achieves finer-grained access control than existing filtering methods by accumulating context information and distributing filter stages. We enhance conventional filter criteria—such as network address, port number, or transport protocol—by including security labels and context information. Security labels store secrecy levels, integrity levels, and categories. Context tags (contags) accumulate context information, e.g., over which incoming link a data packet was received or whether a data packet was received over protected links. This information can be examined by subsequent, possibly remote, filter stages. The authenticity of these filter criteria is crucial for the overall security. We use the history information accumulated in a data packet itself to establish trust in the included filter criteria. We focus on the structure of distributed 3-stage filters comprising receiving inspection, tagging and re-labelling, and filtering. An example shows how to use context information to improve access control for signalling networks in a heterogeneous service provider environment. This is a pre-requisite for opening service interfaces in global telecommunication networks.