R. Battiti, M. Conti, and R. Lo Cigno (Eds.): WONS 2004, LNCS 2928, pp. 184–198, 2004. © IFIP International Federation for Information Processing 2004 Dependable and Secure Data Storage in Wireless Ad Hoc Networks: An Assessment of DS 2 S. Chessa 1,2 , R. Di Pietro 3 , and P. Maestrini 1,2 1 Dipartimento di Informatica, Università di Pisa, via Buonarroti 2, 56127 Pisa, Italy 2 Istituto di Scienza e Tecnologie dell’Informazione “A. Faedo”, Area della Ricerca CNR, via Moruzzi 1, 56124 Pisa, Italy 3 Dipartimento di Informatica, Università di Roma “La Sapienza”, via Salaria, 113 – 00198 Roma, Italy Abstract. DS 2 is a dependable and secure data storage for mobile, wireless networks based on a peer-to-peer paradigm. DS 2 provides support to create and share files under a write-once model, and ensures data confidentiality and de- pendability by encoding files in a Redundant Residue Number System. The pa- per analyzes the code efficiency of DS 2 using a set of moduli allowing for effi- cient encoding and decoding procedures based on single precision arithmetic, and discusses the security issues. The comparison of DS 2 with the Information Dispersal Algorithm approach (IDA) shows that DS 2 features security features which are not provided by IDA, while the two approaches are comparable from the viewpoint of code efficiency and encoding/decoding complexity. 1 Introduction Mobile ad hoc networks are composed by a set of mobile hosts (also called mobiles) communicating with each other via radio transceivers. In order to communicate with destinations which are located outside of their transmission ranges or hidden by ob- stacles, communicating mobiles rely on other mobiles which cooperate to forward messages to their destinations. To this purpose the network layer of the mobiles pro- vides services of message delivery by running suitable routing algorithms [1], [2]. However, mobility and failures may give rise to network disconnections impairing service dependability. Due to mobility of nodes, the network topology varies with time. At a given instant of time it is described by a graph where nodes are the mobiles, and a link connecting two nodes in the graph means that the corresponding mobiles can communicate di- rectly. The mobiles rely on on-board batteries for energy supply, hence energy efficiency of mobiles is an important issue [3]. The effect of battery depletion is similar to a crash fault, from which the mobile may or may not recover depending on the avail-