In applications such as remote file storage systems, an essential component of cloud computing systems, users are required to rely on untrustworthy servers. We outline an approach to secure such file storage systems by relying only on a resource limited trusted module available at the server, and more specifically, without the need to trust any component of the server or its operator(s). The proposed approach to realize a trusted file storage system (TFSS) addresses some shortcomings of a prior effort (Sarmenta et al., 2006) which employs a merkle hash tree to guarantee freshness. We argue that the shortcomings stem the inability to verify non- existence. The TFSS described in this paper relies on index ordered merkle trees (IOMT) to gain the ability to verify non-existence.