Peter Lyko defended his Master's thesis on 'Secure deletion on mobile devices with Android'

The Master Thesis deals with the process of secure deletion on Android- Smartphones. Deleting a file causes the operating system only to remove the reference to it, but not its content. As long as this file content is not overwritten, it can be recovered. Android runs under a Linux OS, so it also has this problem. If the user of a Smartphone sells his device, user data could remain in the memory. This work introduces a solution to this problem.
At the beginning, three subject areas, which are the bases of this work, will be discussed. The first one is user data under android. Using the reference device Samsung Galaxy S3, each partition has been investigated to find the location of user data. The second subject area includes the deletion in itself and especially on NAND memory. The third branch includes the mobile forensic techniques which allow evaluating a secure deletion. Over the usage of a smartphone the stored data change often. The reasons for this can be found within the life cycle of files.
Deletion is the last part of the life cycle of a file. The different ways of data deletion on Android provide an approach for secure deletion. Using the devices Samsung Galaxy S2 and S3, investigations have revealed whether secure deletion without the use of third party software is possible. In doing so, the system recovery as well as the available options of manual deletion was investigated. These investigations lead to differing results. Thought the system recovery delivers a possible alternative to secure deletion, this does not apply to each device. The options of deletion of the above-mentioned devices have gaps in security.
As a result of this work, a concept is presented that allows permanently deleting user data, as they occur on an Android smartphone, in a running system. Moreover, the result includes an Android application that implements a part of the introduced concept.