Using optical microscopy for data recovery…

Optical media especially CDs and DVDs are ubiquitous, but recovering data from them is often not economical. Beyond light scratching and superficial media damage, recovering data is often not economical. Our data recovery experts see optical media that has been broken into several pieces and unless the information is of critical importance, data recovery is simply not viable.

Factory pressed and home-burned media use different technologies. The first burns physical pits into the media and the second causes colour changes in the film layer. By using 3D Laser Microscopy we can create a magnified image of the media. The data is written in a spiral rather than concentric tracks, so when media is in several pieces, this can prove a challenge. However high magnification and precise measurement allows us to effectively ‘piece together’ the disc.

Once we have an image of the binary source code, by reversing the encoding algorithm which divides the data into segments, we can identify areas of data and areas of error correction. These algorithms do not encode the data, but ensure data is stored efficiently and redundantly. These algorithms are easy to obtain and with only a handful of variants, it should not take long to identify the precise one.

When we have cracked the algorithm it is then a case of rebuilding the data from a binary level upwards. Whilst this all sounds straightforward, it is a time consuming process and recovery of all the information is rare. Data ‘holes’ in the final output are commonplace, but often enough of the jigsaw can be pieced together to provide enough recovered information.

Due to the economical restrictions this technology is used mostly by our computer forensics team, where the data is of paramount importance. Indeed our findings have been instrumental in the outcome of many high profile cases.