Polybius square
Cuadrado de Polibio
- Date
- c. 150 BCE · confidence low
- Place
- Greece
- Credited to
- Cleoxenus and Democleitus (invention); Polybius (popularization)
- Field
- Communication
What it is
A device encoding each letter of the alphabet as a pair of numbers on a grid, originally devised for torch-based signalling and later used in cryptography and steganography; attributed to Cleoxenus and Democleitus, and popularized by the historian Polybius.
What it led to
- Long-distance optical signalling systems
- Later substitution ciphers
- Basis of military ciphers such as WWI's ADFGVX