Application Notes
Maximizing Data Recovery: Utilizing 3D Digital Laser Microscopy to Image Damaged Optical Media
Executive Summary
Our research and practice in Information Technology and Digital Forensics has encountered many situations where stored digital information is highly desired but its storage media has been damaged. This led to the development of a sponsored research project with the National Science Foundation to explore the potential for recoverability of data from damaged media.
Olympus LEXT OLS4100 Laser Scanning Confocal Microscope
Methodology
Figure 1: Image of a damaged home-burned CD. Pits and lands (encoded data) are visible as gray and white dots and dashes. These patterns were converted to 0s and 1s, then decoded to recover the original data.
Figure 2: A string of dots and dashes selected for decoding.
We measure each dot and dash, then reverse the encoding algorithm used to convert the original data into the dots and dashes that were subsequently written to the media. There are only a handful of encoding algorithms in wide use, and most of these are publicly available. These algorithms don't encrypt the data, rather they simply encode it such that the information is stored efficiently and redundantly. This redundancy is significant for data recovery because it means that limited damage might not destroy all copies of original data, and we have a better chance of recovering more of the original data even in cases where we don't have the complete original media.
Figure 3: Image of optical disc in multiple pieces.
Media that has been willfully destroyed such as a disc broken into multiple pieces is something that has particularly gained our attention because to a large degree the data often stays intact—it just has a damaged "container." Figure 3 depicts such a disc—we can visually see that the data appears to have suffered little impact as a result of the trauma. Using the LEXT OLS4100, we can measure the data patterns to confirm whether or not data impact has occurred. If it has, it may still be possible to adjust algorithms to handle the impact of the damage and recover the data based on the measurements.
High magnification allows for precise measurement that can be used to help develop potential ratios for data analysis and recovery. Figure 4 is an example of a high-resolution max zoom image of data on an optical disc.
As of this writing, we have recovered data using manual decoding. Efforts are currently underway to automate this process with a computer program. The main instrument that we utilize to gather information from optical media to evaluate for potential recovery is the OLS4100, which provides the 3D visualization and measurement aspects critical to obtaining usable information from optical media. Figure 5 is a 3D data image from an optical disc.
Figure 4: 17120x max zoom image of a damaged DVD
Figure 5: 3D image of data on an optical disc.
Conclusions
There are many implications to our work. One is simply recovering data that was thought to be lost. Another is just the opposite. By understanding the characteristics that allow for potential data recovery, security techniques can be adapted so that data is unrecoverable. As an example, a common way to destroy a paper document used to be to burn it. Forensic techniques however were developed that allowed for the recovery of information that on a burned document. Document destruction techniques were then improved to account for potential forensic techniques.
While we don't purport to have solved all of the challenges necessary for efficient data recovery from damaged optical media, we have moved the ball forward in terms of refining what is possible.
Our work has been supported by the National Science Foundation under Grant No. 1116268. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
Greg Gogolin, Ph.D. (Ferris State University)
James Jones, Ph.D. (George Mason University)
Derek Brower, M.S. (Ferris State University)
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