Measuring and limiting the covert channel risk of XML document transmission

This paper discusses the transfer of XML documents from a classified to a less classified or unclassified domain. We describe the risk of unwanted covert data transmission associated with it and propose a guard mechanism to limit the maximum possible data rate of this covert channel. We take the known structure of XML messages used by specific protocols into account. We present a demonstrator implementation of the guard mechanism and show how it can be used to transfer NETCONF management traffic.