Cryptography Reference
In-Depth Information
Document-Tracking Tools
Hidden information can identify the le-
gitimate owner of the document. If it is leaked or distributed
to unauthorized people, it can be tracked back to the rightful
owner. Adding individual tags to each document is an idea at-
tractive to both content-generating industries and government
agencies with classified information.
File Authentication
The hidden information bundled with a file can
also contain a digital signature certifying its authenticity. A reg-
ular software program would simply display (or play) the doc-
ument. If someone wanted some assurance, the digital signa-
ture embedded in the document can verify that the right person
signed it.
Private Communications
Steganography is also useful in political
situations when communications is dangerous. There will al-
ways be moments when two people can't exchange messages
because their enemies are listening. Many governments con-
tinue to see the Internet, corporations and electronic conver-
sations as an opportunity for surveillance. In these situations,
hidden channels offer the politically weak a chance to elude the
powerful who control the networks. [Sha01]
Not all uses for hidden information come classified as stegano-
graphy or cryptography. Anyone who deals with old data formats and
old software knows that programmers don't always provide ideal data
structures with full documentation. Many basic hacks aren't much
different from the steganographic tools in this topic. Clever program-
mers find additional ways to stretch a data format by packing extra
information where it wasn't needed before. This kind of hacking is
bound to yield more applications than people imagined for stegano-
graphy. Somewhere out there, a child's life may be saved thanks to
clever data handling and steganography!
1.0.4 Attacks on Steganography
Steganographic algorithms provide stealth, camouflage and security
to information. How much, though, is hard to measure. As data
blends into the background, when does it effectively disappear? One
way to judge the strength is to imagine different attacks and then
try to determine whether the algorithm can successfully withstand
them. This approach is far from perfect, but it is the best available.
There's noway to anticipate all possible attacks, although you can try.
