A P2P Backup System for Small and Medium-sized Enterprises

This thesis presents the design and implementation of the All-or-Nothing package transform, presented by Ronald Rivest in 1997 [24], and its subsequently integration in an existing peer-to-peer backup system. This encryption mode provides a third alternate way of ensuring confidentiality, integrity and availability of backups. Resilia, the existing prototype where this extension is built on, combines peer-to-peer technology with secret sharing and distributed backup algorithms in order to provide a robust, safe and secure environment for backups, required by decentralized and off-site storage of data. The backup schemes used by the application increase the availability of the distributed data and achieve an efficient space and communication usage, if associated with a replication scheme, allowing the reconstruction of backups even in the case of failure of some peers. The evaluation of the designed and implemented package transform revealed good results, taking 25 seconds to compute and distribute a 10 Mb backup file to 3 peers. Discovering and fixing a tampered share in one of the peers took approximately 7 seconds, considering the time to re-send the backup file to the incorrect peer. The thesis deals with the applicability of different secret sharing algorithms or distributed backup in a peer-to-peer system. In particular, it implements the All-or-Nothing package transform proposed by Ronald Rivest [24]. The developed system integrates with an existing safe and secure backup system which implements an information dispersal algorithm and a secret sharing scheme. Acknowledgements First, I thank my supervisor Christian D. Jensen for his support, guidance and good comments throughout the project. And also for believing in me for the second time. My family, in particular my wife and son, are specially thanked for the love, support and patience for all the time I spend on the computer. Last, a huge thanks is due to all who helped me throughout the project. To Dagur Gunnarsson and Tore Bredal Nygaard for good comments and motivation during different stages of the project, and to Raghav Karol and Ana Giral for providing good company during the time we shared the office.