Cryptographic transforms for a lightweight and efficient DVB link-layer security extension

The Unidirectional Lightweight Encapsulation (ULE) and the Generic Stream Encapsulation (GSE) protocol have been defined as extensible mechanisms for the efficient carriage of IP data over Digital Video Broadcasting (DVB) links, but, in keeping overhead at minimum, they do not include any security functionality. This is an issue for DVB broadcast links, which are vulnerable due to their typically large coverage areas and the direct accessibility of a wireless communications channel, making eavesdropping easy. A list of security requirements for DVB networks has been derived jointly with independent authors in RFC 5458, and a joint security extension header design for the ULE protocol has been presented. This paper first describes a revised security extension header, which is applicable for both ULE and GSE as well as future GSE-like protocols such as defined in the new DVB-RCS2 standard. It then presents a set of cryptographic transforms to address each of the traffic security requirements identified. In particular, effective measures against traffic flow analysis attacks are described, which are of concern not only to military applications. The benefits of the proposed mechanisms are highlighted and contrasted in terms of bandwidth overhead and security functionality to traditional IPsec tunnel mode encapsulation and to base-band frame security such as envisaged for the DVB-RCS2 standard.