In Plutus, we trust servers to store data properly, but not to keep data confidential. While a server in Plutus may attempt to change, misrepresent, or destroy data, clients will detect the malicious behavior.
Cryptography alone, however, cannot prevent destruction of data by a malicious server. Replication on multiple servers can ensure preservation of data even when many of the servers are malicious. Systems such as BFS [7], Farsite [1], OceanStore [25], PASIS [17], PAST [12], and S4 [47] address techniques for secure availability through replication. Though, in this paper, we restrict our focus to securing data on a single untrusted file server, the ideas could be generalized for a set of replicated file servers.