Authenticated and persistent skip graph: a data structure for cloud based data-centric applications

Cloud computing has evolved as a popular computing environment. In data centric applications hosted on the cloud, data is accessed and updated in a purely distributed manner. The distributed data structures used for dynamic storage of the data for such applications require two fundamental qualities, authentication and persistence, which are not completely met by existing distributed data structures. Authentication is a crucial requirement for data structures used on the cloud, as users need to be convinced about the validity of the data they receive. Moreover the data structure has to be persistent, so that changes can be made to the data structure without losing old data, or old versions of the data structure, which may be required by different users in the distributed environment. In this paper we present authenticated and persistent skip graph, an enhanced variant of the existing skip graph. It is based on an event based model, to correspond to the distributed data centric application requirements. Skip graphs are randomized data structures based on skip lists, proposed for use in distributed applications. But skip graphs are neither persistent nor authenticated. The fat node technique is adapted here for providing persistence, and a role based access control, with a cryptographic scheme is used to ensure valid data update and verify the validity of the retrieved data. Our data structure is proved to be efficient in terms of time and space complexities.