Certificateless Provable Data Possession Protocol for the Multiple Copies and Clouds Case

For user's extremely important data, storing multiple copies on cloud(s) may be a good option because even if the integrity of one or more copies is broken, it can still recover data from other intact ones, which increases the availability and durability of the outsourced data. Some provable data possession (PDP) protocols guaranteeing the integrity of multi-copies had been proposed in the past years. But almost all of them considered storing multi-copies to single cloud, and the necessary management of certificates as well as the dependence on PKI greatly decrease their efficiencies. Therefore, in recent work, Li et al. proposed an identity-based PDP protocol, which not only avoids the tedious certificates and PKI, but also supports muiti-copies stored on multi-clouds. However, it is well-known that identity-based protocols suffer from the key-escrow attack. In this paper, we consider the certificateless multi-copy-multi-cloud protocol. Specifically, we first present its security model and then construct a concrete protocol, whose security can be proven under the classical CDH assumption. Finally, the performance analysis demonstrates that our protocol yields better efficiency and hence is practical.