Intelligence can make or break you on the battlefield, as
well as in the boardroom. At one time the only option for front line leaders
was to gather information, analyze it on the fly, and take their best shot.
Over time, as intelligence gathering became more sophisticated, and analysis
became more centralized, analysis was often made far from the front lines. This necessitated that decisions,
strategies, and plans be transmitted back to commanders in the field, securely
and in a timely fashion.
Over the years there have been many ingenious ways of
transmitting information securely, some better than others. One method known as
steganography hides the message in plain sight. For example, if Cesar needed to
get a message to field commanders he may have had it written on a soldiers belt
that had first been wrapped about the standard staff, carried by all high
ranking officers. A messenger wearing the belt would then travel to the front
lines. On arrival his belt would be removed and re-wrapped around the proper
diameter staff, revealing the message. If the belt fell into enemy hands, the
inscriptions on it would appear to be nonsense. Not very secure, but better
than nothing. As children, most of us experimented with invisible ink of one
kind or another. In some cases, the misplacement of commas and periods in an
otherwise innocent looking letter has been used to carry a coded message. All
are ways of hiding a message in plain sight.
By the time of the Civil War the telegraph was used to
convey information from central command to officers in the field. With the
Great War came the use of wireless, and along with both, the need for some kind
of encryption. Encryption methods vary in complexity from the simple shift
codes to variations of the box code. Shift codes are implemented by shifting
letters up a given number of characters. Shift-one would have you shift each
letter up one character in the alphabet to encode, and down one to decode.
Perhaps the most famous example of this, according to some, is the name of the
computer in Space Odyssey 2001. Shift the letters for HAL up one letter to see
what I mean. Box codes are arrays of letters, often five rows of five letters
each. Messages are spelled out by giving the row and column of the letters in
the box that form the message.
There is a downside to box and shift codes. Any one who has
studied Morse code knows that some letters are used more than others. This is
the reason the most used letter in the English language, e, is a single dot.
The next most used letter is t, a single dash. More popular are the i’s and m’s
followed by the s’s and o’s. Given this information, you can see how someone
could decode a message using something like the shift or box codes, by
replacing the most frequently occurring letter with an e, next most with a t,
etc.
A more secure method might be something as simple as a copy
of a novel that everyone who needs to code or decode messages has in their
possession. This was the basis for the plot of the film “ Three Days of the
Condor.” To send a message, randomly pick a page, that contains the first
letter and code it with the page number, line number, and the number of
characters from the beginning of the line.
Repeat for each letter in the message. Only those who know the
procedure, and have a copy of the same edition of the novel will be able to
decode the message. With this type of encryption, character frequency is not
going to be of much help. Mechanical devices have been devised to do something
similar. The famous Enigma machine is one example of this. Similar to a
typewriter it could be made to scramble letters of a message, in random
fashion, and more importantly, could be rewired on a regular basis to be extra
sure that letter patterns were not detectable.
Codebooks and machines have the disadvantage that they may
fall into the wrong hands. One way around this is a technique used in PGP,
which stands for pretty good privacy. Here two keys are needed to unlock a
message. One is public, the other private. This eliminates the need for
everyone to have the same codebook. If it becomes known that one persons
private code has been jeopardized, one simply needs to not send that person any
information you would rather not fall into the wrong hands. The private key is
only good for decoding messages sent to its holder.
In many instances it is not necessary to know the content of
the message to gain intelligence. For example, if it is observed that several
stations are all reporting to one station, it is a good bet that the station
reported to is headquarters, and by using triangulation it is possible to
locate it as well as all reporting to it.
The evolution of encryption and intelligence gathering
techniques continues to grow with new technologies, and ever improving methods
of data collection and analysis, conducted by large government organizations
like the NSA.
