Consider the following problem. Alice and Bob are prisoners who
are allowed to communicate via e-mail; they wish to use this communication
channel to make escape plans. Unfortunately, the prison warden,
Ward, monitors the email between prisoners and if he detects the
slightest evidence that Alice and Bob are planning an escape,
he will throw them in solitary confinement. So Alice and Bob need
to communicate secretly, without appearing to do so. They need
to use steganography.
Steganography, literally meaning, covered writing", refers to
the task of communicating secret messages over a publicly observable
channel in a way which conceals the very existence of a message.
A recent paper by Hopper, Langford and von Ahn gives the first
steganographic protocols which have rigorous proofs of security.
The authors show several constructions and prove that if certain
cryptographic primitives exist, then these constructions can be
instantiated by steganographically secure protocols. These protocols
are also unusual in that they are the first known protocols (provably
secure or not) that can hide information in unformatted, plain
text. An important application of these protocols is as proofs
of authorship. Anyone who hides information in a text using these
protocols can later prove authorship of that text using zero knowledge
proofs of knowledge. Thus these protocols can be used to protect
intellectual property in both academic and corporate settings.
The embedding performed by these protocols is the result of an
> interactive process between the stegosystem and a user. So any
implementation will require an interactive environment such as
a text editor. We have chosen XEmacs.