If you read the paper, the security they are referring to is most likely that their data model is similar to git, using Merkle trees to ensure the integrity of

If you read the paper, the security they are referring to is most likely that their data model is similar to git, using Merkle trees to ensure the integrity of files and their histories: > Our data model, like that of Git, forms a Merkle tree in which the Commit forms the root of the tree pointing to the root Tree object and previous Commit object(s). The root Tree object points to Blobs and other Tree ob- jects that are recursively encapsulated by a single hash. Ori supports signed commit objects, by signing the seri- alized Commit object with a public key. The Commit ob- ject is then serialized again with the key embedded into it, thus forcing subsequent signatures to encapsulate the full history with signatures. To verify the signature we recompute the hash of the Commit object omitting the signature and then verify it against the public key. The filesystem they describe has a few other very interesting features that paint it as a possible replacement for something like Dropbox, or even a network filesystem like NFS. You should check it out.