JerryB said:
But surely any agent listening in would know that he/she was tuned into the right station? After all, one assumes that the frequency is known to the agent beforehand.
So would the Enemy and any number of other spies if only the frequency were used to identify the broadcast part of the code.
Since the simple Caesarian cypher (a=b, b=c, and so on) crytography has become so complex and multi-layered it would make your head explode if you actually knew what was going on.
The humble book code mentionned at the beginning of this thread is inadequate for serious purposes because all you have to do to find the book is rummage around--
Our Man in Havana gives a good idea of how easy this is and what the consequences can be.
Given enough time and motivation, there is no reason why a single numbers transmission could not carry several channels of informatin, some obvious but secure, like the numbers, some mechanical and meant only for machines, and some so craftily hidden as to be impossible to detect. Like the Internet, a little something for everybody--a simple code for the spy on the run, more complex codes for more valuable messages, and impossible to crack mathematical codes allowing supercomputer owners to talk to each other.
I have been thinking of different ways to encrypt my passwords myself. I would like to have a multilayered, multipurpose system that allows me to recuperate my passwords in an appropriate time span regardless of whether I am dealing with my bankcard or a one time login on a website of no particular importance. But memory and time are the great enemies of secrecy. To be simple enough to be memorable, a system would have to be simple enough to crack.
Hence numbers stations, which can service any number of spies with any number and quality of codes and cyphers. It's possible that nobody knows what is being broadcast--a computer may be generating random numbers and another computer turning them into one time pads or something even more elaborate.
I can tell you one thing--since I read about the sort of people who put their password on a sticky note under the keyboard, there is a sticky note under my keyboard which reads "Ceci n'est pas un mot de passe."
