Six Lines

Hard Drive Steganography

Posted by Aaron Massey on 25 Apr 2011.

New Scientist wrote about a recent paper on using hard drive fragmentation to hide information. You can find the paper through its DOI: 10.1016/j.cose.2010.10.005.

Hard drive fragmentation occurs when the 1′s and 0′s that make up a file cannot be stored next to one another physically on a hard drive. We may often think about digital information as completely non-physical, but that’s just an abstraction. In reality, there is a physical medium for each 1 and each 0 somewhere.

This paper describes a technique of hiding a message (also composed of 1′s and 0′s) by fragmenting a hard drive according to a code. Here’s how their technique is described by New Scientist:

The code depends on whether sequential clusters in a file are situated adjacent to each other on the hard disc or not. If they are adjacent, this corresponds to a binary 1 in the secret message. If sequential clusters are stored in different places on the disc, this encodes a binary 0. The recipient then uses the same software to tell them the file’s cluster positions, and hence the message. The researchers intend to make their software open source.

Hiding messages like this is called steganography, and it can be a useful security technique. Again, as New Scientist describes:

Encryption should sometimes be avoided, says Hassan Khan at the University of Southern California in Los Angeles, because the gobbledegook it creates is a dead giveaway: it shows someone might have something to hide. That could spell disaster for someone trying to smuggle information out of a repressive country.

Definitely read the article, and if you can skim their paper online. It’s worth a read.