How to Solve the ADFGVX Cipher

A grid cipher lays the alphabet out in a square — usually 5×5, with I and J sharing a cell — and describes each letter by where it sits. Some stop there; others shuffle those coordinates or push pairs of letters through the square together.

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How to recognise it

Digits that never go above 5, or letters drawn from a tiny set like A, D, F, G, V and X, mean coordinates. Ciphertext that always comes in an even number of letters points to a cipher that works on pairs.

ADFGVX Two keys, two steps. The 6×6 square starts with TREASURE and runs on through the alphabet and 0–9; each letter became its row and column label. Then the whole stream was written under GOLD and read out column by column in alphabetical order.

A worked example

The alphabet sits in a square, and every letter is described by where it lives. Get the square right and the rest is bookkeeping. This one is ADFGVX. The key: square TREASURE · columns GOLD. Two keys, two steps. The 6×6 square starts with TREASURE and runs on through the alphabet and 0–9; each letter became its row and column label. Then the whole stream was written under GOLD and read out column by column in alphabetical order. Look the first pieces up in the square and they come out T R E. The answer was TREASURE MAP.

Working one out from scratch

Draw the square first, keyword and all, and keep it in front of you. Nearly every mistake on a grid cipher is a square built wrong — a repeated keyword letter left in, or J given its own cell.