Volume 12, Number 13, July 2022

A Method to Compactly Store Scrambled Data Alongside Standard Unscrambled Disc Images of CD-ROMs

  Authors

Jacob Hauenstein, The University of Alabama in Huntsville, USA

  Abstract

When archiving and preserving CD-ROM discs, data sectors are often read in a so-called “scrambled mode” before being unscrambled and further processed into a standard disc image. Processing of scrambled data into a standard disc image is potentially lossy, but standard disc images exhibit greater software compatibility and usability compared to scrambled data. Consequently, for preservation purposes, it is often advantageous to store both the scrambled data and the corresponding standard disc image, resulting in high storage demands. Here, a method that enables compact storage of scrambled data alongside the corresponding (unscrambled) standard CD-ROM disc image is introduced. The method produces a compact representation of the scrambled data that is derived from the standard disc image. The method allows for storage of the standard unscrambled disc image in unmodified form, easy reconstruction of the scrambled data, and a substantial space savings compared standard data compression techniques.

  Keywords

compact disc, compression, data archival, data preservation, scrambled.