1. A multi-level security system, the system comprising: a storage medium, the storage medium partitionable into a plurality of partitions; a file system coupleable to the plurality of partitions; a plurality of enclaves each assigned a security classification level, wherein each one of the plurality of enclaves resides in a different storage partition of the storage medium; wherein data stored on the storage medium is cryptographically separated at rest on a per-enclave basis, and wherein cryptographic separation occurs at the disk block level thereby allowing individual blocks to be read and decrypted; wherein every disk block is encrypted using a unique key for each security classification level; and a reference monitor that enforces a system security policy that governs access to information between the plurality of enclaves, wherein the reference monitor allows an enclave of the plurality of enclaves having a first classification level to securely read-down to another enclave of the plurality of enclaves having a second classification level lower than the first classification level and to write to another enclave of the plurality of enclaves having the first classification level.