The first cryptographic method recorded in history was scytale, which was used for sending messages in times of war. It was invented in the 6th century B.C. and it was based on the transposition of the letters that formed the message. The famous Acarnanian General Aeneas Tacticus describes some excellent cryptographic methods, such as the use of a combination of dots instead of vowels (e.g. Διονύσιος καλός – Δ :: :·: Ν ::: Σ :: :·: Σ Κ · Λ :·: Σ) or the use of marked letters on an irrelevant message in his “Poliorcetica” treatise. He also devised an ingenious cryptographic disk.