Cryptography Reference
In-Depth Information
With this in mind, manufacturers try to accommodate hidden, mostly irremov-
able information about the author in digital documents; we also speak of
digital
watermarks
(copyright marking systems). A digital signature wouldn't help
since it can be easily removed. A good example is the protocol by Birgit Pfitz-
mann described in [Pfitzfinger], which safeguards the anonymity of the honest
customer.
However, in this hide-and-seek game, too, there are ways to make hidden infor-
mation unusable, if it cannot be protected. Perhaps the first attack of this type
against steganographic methods is described in [PetAndMark]. The authors
are convinced that this type of analysis has helped steganography in making
progress just as cryptanalysis has furthered cryptography. I understood from
their work that the development of automatic tests for revealing hidden infor-
mation is still in its infancy — at least in the civilian sector. [Ditt] is a topic
that thoroughly discusses the possibilities and risks.
