It seems reasonable to assume that people have tried to conceal information in written form since writing was developed and examples survive in stone inscriptions and papyruses showing that many ancient civilisations including the Egyptians, Hebrews and Assyrians all developed cryptographic systems. The first recorded use of cryptography for correspondence was by the Spartans who (as early as 400 BC) employed a cipher device called a "scytale" to send secret communications between military commanders. The scytale consisted of a tapered baton around which was wrapped a piece of parchment inscribed with the message. Once unwrapped the parchment appeared to contain an incomprehensible set of letters, however when wrapped around another baton of identical size the original text appears.
The Greeks were therefore the inventors of the first transposition cipher and in the fourth century BC the earliest treatise on the subject was written by a Greek, Aeneas Tacticus, as part of a work entitled On the Defence of Fortifications. Another Greek, Polybius later devised a means of encoding letters into pairs of symbols using a device known as the Polybius checkerboard which contains many elements common to later encryption systems. In addition to the Greeks there are similar examples of primitive substitution or transposition ciphers in use by other civilisations including the Romans.
The Polybius checkerboard consists of a five by five grid containing all the letters of the alphabet. Each letter is converted into two numbers, the first is the row in which the letter can be found and the second is the column. Hence the letter A becomes 11, the letter B 12 and so forth.
Early Cryptographic Systems
It seems reasonable to assume that people have tried to conceal information in written form since writing was developed and examples survive in stone inscriptions and papyruses showing that many ancient civilisations including the Egyptians, Hebrews and Assyrians all developed cryptographic systems. 