Post by William Unruh...
Post by Mok-Kong ShenPost by William UnruhIt is called pgp. You just encrypt your message. No need to anticipate
the questions beforehand. It can ge used for any possible message you
would want to send, even unforseen ones. Why the need for
steganography. Sure you could agree with your boss that if dogs are
mentioned int he message you mean yes, and if cats, no.
But steganography is limited to the rare cases when the fact that you
are using hiding should not be obvious to anyone, requires lots of
advance preparation, and is completely obvious unless you are really
creative in the way you manufacture the message. It is also horrendously
"expensive" (transmitted text much much much larger than the message to
be sent).
Note that this type of crypto is ancient. It is also pretty limited in
its usefulness. Modern crypto means that you do not have to worry about
your message being readable. No Stego needed.
I don't understand why you want to unconditionally neglect certain
feasible alternatives which under suitable conditions could be useful.
Analogy: If you have a motorcycle, you can from your home extremely
fast reach any arbitrary point of your city. But in some cases riding
a bicycle may be just as fine and perhaps also more enjoyable, though
the radius of reachability is for practical reasons comparatively
limited and it takes more time to get to your destinations.
Enjoyable? You can play whatever games you want, by yourself. Your
attitude presents a really silly approach to crypto. It is a deadly
serious business, and advocating bad crypto to people whose lives may
depend on it is not very good. It is extremely labourious, and, like a
one time pad, is really bad for repeated use. It is extremely limited in
the messages it can send. Sure it could be useful in extremely special
and limited cases, and has been used that way for decades and on every
TV show. (Just last week I watched on in which a person was wired up an
in a nest of criminals, and if he mentioned chickens his collegues
should rush in and rescue him.)
IMHO your example actually supports the usefulness/efficiency of
steganography.
Anyway, I don't agree with your one-size-fits-all strategy. Even for
hammers, one commonly would need different sizes of them, depending
on the nails.
As to the work being laborious, everything of utility in life has
its corresponding cost, cf. the Principle of No Free Lunch. Consider
my earlier example: Wouldn't the upper bound of the cost of devising
a stego scheme be substantially high, if the competition were something
like, say, between Boeing and Airbus for the sale of 100 machines?
(Actually longtime ago there were rumours that in one case Airbus
failed to get the contract as consequence of espionage.)
Note that in my earlier example the communications between the
representative and his manager could under circumstances contain
stuffs that would be disadvantageous to the firm -- not only for the
present but also in the future -- if these became known to the
customer. Now, if encryption is used, then in countries like the
UK there is the risk of law enforcement's demanding delivery of the
key. In that case the content of the message would not only be
releaved but also proved to be genuinely stemming from the firm.
In the stego alternative, the content wouldn't be known, since the
cover message is innocent, not to say could be proved to be genuine.
M. K. Shen