Editing Covert channel (section)

==Data hiding in OSI model==

Handel and Sandford presented research where they study covert channels within the general design of network communication protocols.<ref name="handelSandford">[http://faculty.kfupm.edu.sa/COE/mimam/Papers/96%20Hiding%20Data%20in%20the%20OSI%20Network%20Model.pdf Hiding data in the OSI network model] {{webarchive|url=https://web.archive.org/web/20141018041347/http://faculty.kfupm.edu.sa/COE/mimam/Papers/96%20Hiding%20Data%20in%20the%20OSI%20Network%20Model.pdf |date=2014-10-18 }}, Theodore G. Handel and Maxwell T. Sandford II (2005)</ref> They employ the [[OSI model]] as a basis for their development in which they characterize system elements having potential to be used for data hiding. The adopted approach has advantages over these because standards opposed to specific network environments or architectures are considered.

Their study does not aim to present foolproof steganographic schemes. Rather, they establish basic principles for data hiding in each of seven [[OSI layer]]s. Besides suggesting the use of the reserved fields of protocols headers (that are easily detectable) at higher network layers, they also propose the possibility of timing channels involving CSMA/CD manipulation at the physical layer.

Their work identifies covert channel merit such as:
* Detectability: Covert channel must be measurable by the intended recipient only.
* Indistinguishability:  Covert channel must lack identification.
* Bandwidth: number of data hiding bits per channel use.

Their covert channel analysis does not consider issues such as interoperability of these data hiding techniques with other network nodes, covert channel capacity estimation, effect of data hiding on the network in terms of complexity and compatibility. Moreover, the generality of the techniques cannot be fully justified in practice since the OSI model does not exist per se in functional systems.