cluster based steganography

Eugen Leitl eugen at
Tue Apr 26 02:33:47 PDT 2011

Boffins devise way to hide secret data on hard drives

Technique evades forensics investigations

By Dan Goodin in San Francisco b" Get more from this author

Posted in Security, 26th April 2011 02:25 GMT

Computer scientists have developed software that hides sensitive data on hard
drive, without the use of encryption, by controlling the precise disk
locations containing the file's data fragments.

The application, which the academic researchers said they would release as
open-source software, makes use of steganography, or the ancient art of
hiding secret information in plain sight. The technique has long been
employed to keep sensitive data out of the hands of adversaries. The use of
encryption, by contrast, is easy to detect, tipping off adversaries that a
hard drive or other piece of media contains information considered secret.

The software ensures that individual disk clusters that store the sensitive
data fragments are positioned in a way predetermined by their code. A person
who later wants to read the secret information uses the same application to
reassemble the file. The inventors said their method makes it possible to
stealthily store a 20-megabyte message on a 160-gigabyte portable hard drive.

bWe have presented a novel data security mechanism, a filesystem-based covert
channel which allows a user to evade disk forensics by securely hiding data
in a removable or permanent mass storage device,b the researchers wrote in
their paper, titled Designing a cluster-based covert channel to evade disk
investigation and forensics. bInformation is hidden in a manner such that an
investigator is unable to positively prove the existence of hidden data.b

The researchers, from the University of Southern California in Los Angeles
and the National University of Science and Technology in Islamabad, Pakistan,
said the technique may cause only small performance degradations. In some
cases, the approach requires the data to be hidden through the use of a
secret shared between the sender and recipient.

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