The Greek Square Cipher or the Polybius Checkerboard
This week’s cypher is based on a system developed by Polybius, a Greek historian and cryptographer, about 2,000 years ago.
33 15 51 15 42 / 43 44 34 35 / 31 15 11 51 33 24 33 22 / 12 15 13 11 45 43 15 / 31 24 21 15 / 33 15 51 15 42 / 43 44 34 35 43 / 44 15 11 13 23 24 33 22
The key to this code is made by setting up a 6 x 6 square. Leaving the first square blank, number 1 – 5 down and across. Then fill in the remaining squares with the alphabet. Since the English alphabet has 26 letters, it will not fit. I and J occupy the same space, number 24. To encode something, determine first the row then the column number for each letter. A = 11, Z = 55, S = 43.
To determine if a Greek Square is being used, notice that all letters have two numbers and no number is higher than 55.
| 1 | 2 | 3 | 4 | 5 |
1 | A | B | C | D | E |
2 | F | G | H | I, J | K |
3 | L | M | N | O | P |
4 | Q | R | S | T | U |
5 | V | W | X | Y | Z |
The answer to this week’s cipher:
Never stop learning because life never stops teaching.