Polybiuss

Polybiuss is a term commonly used to refer to the Polybius square, a classical substitution cipher attributed to the ancient Greek historian Polybius. The square is a 5-by-5 grid that maps letters to pairs of digits, enabling a plaintext letter to be represented by its row and column coordinates.

In the standard version, the letters I and J share a single cell, giving 25 cells for 26 letters. Each plaintext letter is encoded by a two-digit number corresponding to its position in the grid. For example, A = 11, B = 12, C = 13, D = 14, E = 15, F = 21, G = 22, H = 23, I/J = 24, K = 25, L = 31, M = 32, N = 33, O = 34, P = 35, Q = 41, R = 42, S = 43, T = 44, U = 45, V = 51, W = 52, X = 53, Y = 54, Z = 55. Messages are encrypted by replacing each letter with its two-digit coordinate; spaces are typically omitted or encoded with a special symbol. Variants include larger grids to accommodate digits or punctuation.

History and use: The cipher is traditionally attributed to Polybius, the ancient historian, and is discussed in classical and educational cryptography as an introduction to substitution techniques. While simple and easy to implement by hand or with basic devices, it is vulnerable to frequency analysis and known-plaintext attacks, making it unsuitable for modern security but useful for teaching concepts and in puzzles.

Other uses: In contemporary culture, “Polybiuss” or “Polybius” can also refer to an urban legend about a mysterious arcade game named Polybius, alleged to affect players in harmful ways. The story is widely regarded as fiction and not supported by credible evidence.