Combinatorial Design of Secure Lightweight Data Dispersal Schemes (Work in Progress)

Dispersing a data object into a set of data shares is an elemental stage in distributed communication and storage systems. In comparison to data replication, data dispersal with redundancy saves space and bandwidth. Moreover, dispersing a data object to distinct communication links or storage sites limits adversarial access to whole data and tolerates loss of a part of data shares. Existing data dispersal schemes have been proposed mostly based on various mathematical transformations on the data which induce high computation overhead. This paper presents a novel data dispersal scheme where each part of a data object is replicated, without encoding, into a subset of data shares according to combinatorial design theory. Particularly, data parts are mapped to points and data shares are mapped to lines of a projective plane. Data parts are then distributed to data shares using the point and line incidence relations in the plane so that certain subsets of data shares collectively possess all data parts. The presented scheme incorporates combinatorial design theory with inseparability transformation to achieve secure data dispersal at reduced computation, communication and storage costs. Rigorous formal analysis and experimental study demonstrate significant cost-benefits of the presented scheme in comparison to existing methods.

Fair values and audit fees: Evidence from asset revaluations in Australia

This paper examines the association between the level of audit fees paid and asset revaluations, one use of fair value accounting. This Australian study also investigates attributes of asset revaluations and the association with the level of audit fees paid. We find that firms choosing the revaluation model incur higher audit fees than those that chose the cost model; asset revaluations made by directors lead to the firm incurring higher audit fees than for those made by external independent appraisers; and revaluation of investment properties leads to lower audit fees. The findings suggest that asset revaluations can result in higher agency costs and audit fees vary with the reliability of the revaluations and the class of assets being revalued.