FFS: A cryptographic cloud-based deniable filesystem through exploitation of online web services : Store your sensitive data in plain sight

Abstract: Many Online Web Services (OWSs) today, such as Flickr and Twitter, provide users with the possibility to post images that are stored on the platform for free. This thesis explores creating a cryptographically secure filesystem that stores its data on an online web service by encoding the encrypted data as images. Images have been selected as the target as more data can usually be stored in image posts than text posts on OWS. The proposed filesystem, named Fejk Filesystem (FFS), provides users with free, deniable, and cryptographic storage by exploiting the storage provided by online web services. The thesis analyzes and compares the performance of FFS against two other filesystems and a version of FFS that does not use an OWS. While FFS has performance limitations that make it non-viable as a general-purpose filesystem, such as a substitute for the local filesystem on a computer; however, FFS provides security benefits compared to other cloud-based filesystems specifically by providing end-to-end encryption, authenticated encryption, and plausible deniability of the data. Furthermore, being a cloud-based filesystem, FFS can be mounted on any computer with the same operating system, given the correct secrets.