When files are deleted, their information is not removed from the storage media. This is a well known fact, and there exist numerous undelete utilities to recover newly deleted files. When deleted files have been partly overwritten, the data from the part of the file that remains in unallocated space can be readily extracted by file carving. Such carving is often performed in forensic investigations. Furthermore, as a consequence of file system implementation specifics, there additionally exist small remains of the previous files in the space at the end of new files. In this paper we focus on these small remains of previous files, or micro-fragments, that exist even after all the space allocated to the previous file has been reallocated to new files. We derive expressions for modeling the number of micro-fragments that can be expected to be found, and perform experiments to evaluate the analytical model. The obtained results indicate good correspondence between the analytical predictions and the measured results.
In this paper, we investigate in detail the relationship between entropy and guesswork. The aim of the study is to lay the ground for future efficiency comparison of guessing strategies. After a short discussion of the two measures, and the differences between them, the formal definitions are given. Then, a redefinition of guesswork is made, since the measure is not completely accurate. The change is a minor modification in the last term of the sum expressing guesswork. Finally, two theorems are stated. The first states that the redefined guesswork is equal to the concept of cross entropy, and the second states, as a consequence of the first theorem, that the redefined guesswork is equal to the sum of the entropy and the relative entropy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.