Two-Square Cipher

How Two-Square Cipher works

Two-Square Cipher handles letter pairs by locating the first character in a left keyed square and the second in a right keyed square, then exchanging their columns. The rectangle operation is reciprocal, so applying the same keyed-square transformation decodes. J merges with I, duplicate key letters vanish, and odd input receives X. The Two-Square Cipher exposes its message, left square key, right square key, operation controls so this particular convention stays inspectable instead of hiding behind an unexplained preset.

ATTACKATDAWN under EXAMPLE and KEYWORD becomes EVRCLYEVCBVP; running that output through decode mode returns the original normalized message. The side-by-side square model makes a compact comparison point for Playfair and four-square exercises while retaining its own reversible geometry. The Two-Square Cipher presents a deterministic plain-text result that can be copied and compared with the worked value before it enters another workflow.

Limits and private processing

Two-square conventions vary on same-row pairs; this page consistently swaps rectangle columns for every pair. It is a historical puzzle, not modern encryption. The Two-Square Cipher performs its complete operation locally in your browser; neither the source text nor its settings are uploaded, stored remotely, or sent through an external request.