How to Solve Cryptograms: Tips for Cracking Letter-Swap Ciphers

How the cipher works

Our cryptograms use a simple substitution cipher: each letter of the alphabet is swapped for a different letter, and the swap is the same in every word. If X stands for T once, it stands for T everywhere. No letter stands for itself. Spaces and punctuation are left in place, and they are some of your best clues.

Start with the short words

• One-letter words are almost always A or I.
• Two-letter words: OF, TO, IN, IT, IS, BE, AS, AT, SO, WE, HE, BY, OR, ON, DO, IF, ME, MY, UP, AN, GO, NO, US, AM.
• Three-letter words: THE and AND lead by a wide margin, followed by FOR, ARE, BUT, NOT, YOU, ALL.

Example: if the cipher word XQB appears several times, try THE. Then every X becomes T, every Q becomes H and every B becomes E across the whole puzzle.

Look for patterns

• Apostrophes: a single letter after an apostrophe is usually S or T (IT’S, DON’T). Two letters after it are often LL, RE or VE.
• Double letters: the most common are LL, EE, SS, OO, TT and FF.
• Repeated shapes: a cipher word like ABCA has the same first and last letter; THAT is a good guess.
• Word endings: -ING, -ED, -LY and -TION show up often in quotations.

Use letter frequency to finish

In ordinary English text the most frequent letters are roughly E, T, A, O, I, N, S, H and R. Count the cipher letters in the puzzle: the most common one is a good candidate for E. Frequency works best on longer quotations and is a tie-breaker, not a rule.

A worked example

Take this cipher: UHXX IAQH ZD FHRRHL RTJQ UHXX DJZI.

1. Repeated words. UHXX appears twice and ends in a double letter. Four-letter words ending in a double letter include WELL, TELL, WILL and FALL.
2. The double inside FHRRHL. A six-letter word with a double letter in the middle and the same letter in positions 2 and 5 fits BETTER, so F = B, H = E, R = T and L = R. Then UHXX is _ELL, and WELL is the natural choice: U = W, X = L.
3. Fill in everywhere. With E, T, R, W and L known, RTJQ reads T___ and IAQH reads ___E. THAN and DONE fit, which gives H, A, N, D and O.
4. Finish. DJZI now reads _A_D. SAID fits, so D = S and Z = I, and ZD becomes IS.

The quotation is Benjamin Franklin’s: “Well done is better than well said.” Notice how one confident word (BETTER) opened almost the whole puzzle.

Mistakes to avoid

• Using a letter twice. Each plain letter has exactly one cipher partner. If R already stands for T, nothing else can.
• Sticking with a bad guess. If a guess creates an impossible word, undo it right away; the longer it stays, the more it misleads.
• Trusting frequency too much. In a short quotation, E might appear only once or twice. Patterns beat counting.

A routine that works

1. Solve one-letter words, then try THE and AND on three-letter words.
2. Fill each guess in everywhere and read the partly revealed words.
3. Use apostrophes, doubles and word endings to confirm or reject guesses.
4. If a guess leads to an impossible word, undo it. In our game, Check marks wrong letters in red and Hint places one correct letter.

Practice: play a cryptogram.