Residual information on sanitized magnetic media

While a variety of software tools for the recovery of information from formatted, overwritten, or deleted computer hard drives and floppy disks already exist, none of these technologies are capable of recovering information from demagnetized magnetic storage media. De-magnetization, which is also known as degaussing, is a physical process in which magnetic storage media, is passed through a very powerful oscillating or constant magnetic field. Degaussing is supposed to rearrange the magnetic domains on the media, thereby removing any semblance of the previously recorded signal. Besides physically distorting the original recording, degaussing also results in extremely low recording Signal-to-Noise Ratios (SNR). The SNR after degaussing is far below the sensitivity level of the storage unit's read head and outside its noise filtering and error correction capabilities. Therefore, a degaussed (i.e., sanitized) magnetic media can no longer be read by its original recording system. There are a number of degaussing standards issued by the National Security Agency (NSA), U.K.'s Communications-Electronics Security Group (CESG), and North Atlantic Treaty Organization (NATO) that prescribe how magnetic media must be degaussed to prevent any type of information recovery. It is commonly believed that information recovery from degaussed magnetic media is not possible. The objective of this study was to develop various signal and image processing algorithms for recovering and "descrambling" of residual information patterns from degaussed magnetic storage media.