Hawkynt

Polybius Square

Ancient coordinate-based cipher system that converts letters to coordinate pairs using a 5×5 grid. Invented by Greek historian Polybius around 150 BCE for long-distance communication via torch signals. Forms foundation for many advanced classical ciphers.

Properties

Property	Value
Category	Classical Ciphers
Sub-category	Classical Cipher
Security status	🎓 Educational Only
Complexity	Beginner
Inventor	Polybius
Year	-150
Origin	Not specified
Source	algorithms/classical/polybius.js

Security

Status: 🎓 Educational Only

Known vulnerabilities

Issue	Description	Mitigation
Each letter always maps to same coordinate pair, preserving frequency patterns	—	Educational use only - provides no security by modern standards
Identical plaintext produces identical coordinate patterns making analysis easy	—	Historical demonstration cipher only

Documentation

• Wikipedia Article
• Original Historical Account
• Cryptanalysis Methods

References

• DCode Implementation
• Educational Tutorial
• Tap Code History

Test vectors

3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Plain A-Z square, row then column, both 1-indexed. The Wikipedia article works a different message, so it carries no value for this input

Field	Value
key	(empty)
input	48454c4c4f
expected	3233203135203331203331203334

Vector 2 — Ancient Greek example

Field	Value
key	(empty)
input	504f4c5942495553
expected	3335203334203331203534203132203234203435203433

Vector 3 — I/J equivalence test (J->I conversion)

Field	Value
key	(empty)
input	49555354494345
expected	3234203435203433203434203234203133203135

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