Athos: Efficient Authentication of Outsourced File Systems

We study the problem of authenticated storage, where we wish to construct protocols that allow to outsource any complex file system to an untrusted server and yet ensure the file-system’s integrity. We introduce Athos, a new, platform-independent and user-transparent architecture for authenticated outsourced storage. Using light-weight cryptographic primitives and efficient data-structuring techniques, we design authentication schemes that allow a client to efficiently verify that the file system is fully consistent with the exact history of updates and queries requested by the client. In Athos, file-system operations are verified in time that is logarithmic in the size of the file system using optimal storage complexity—constant storage overhead at the client and asymptotically no extra overhead at the server. We provide a prototype implementation of Athos validating its performance and its authentication capabilities.