Classified message exchange methods have always been of great interest not only to war strategists, but also to diplomats and merchants. The age-old term “cipher” probably originated from the Arabic word “as-sifr”, meaning “zero”. And hence the historic circle encloses, since today’s ciphers are mostly created by computers, as series of ones and zeros.
However, if we do not want to drown in all these ones and zeros (at least when the confidentiality of our message contents is important to us), it is vital to get a clear, albeit general, idea how to create and read such a cipher, what technical and “human” components participate in this process, how they influence each other, and especially what is truth and what is fiction (or a downright deliberate disinformation).
In fact, few fields of the contemporary exact science teem with various myths and disinformation as much as cryptography. It is given not only by the technical difficulty of used methods, not even by its historical roots in military intelligence, but simply by a completely rational fact that (to lighten the topic) if we want to “see the Emperor’s... navel”, instead of fabricating intricate, layered clothes with a refined cut, it is often easier to convince the Emperor that the best clothes are the ones in the classic fairy tale.
Therefore we would like to use this article series to demonstrate the basic facts of contemporary cryptography in a way that will allow the reader to easily verify those facts and use common sense to inspect them in an appropriate context. We will try to conclude each article with a relevant, practical anecdote. Let us begin with the reason why you should read the entire article series carefully - it is, in fact, a matter of life and death!
One of significant historic figures who used her own cipher in letters to her friends was Mary, Queen of Scots. The cipher was relatively elaborate for that time period, but thanks to the amount of captured letters and sufficient time for breaking the cipher, the Queen’s opponents eventually managed to read the contents of her letters. Even though it is not commonly known, this evidence of her consent with the plan to murder Queen Elizabeth I. was a deciding factor in Mary’s execution.