Cryptogram

A cryptogram is a short piece of text written in a substitution code, in which each letter of the alphabet has been replaced by another, so the solver has to work out the original message.

A cryptogram looks like gibberish: "WKH TXLFN EURZQ IRA". Every letter has been replaced by another, using one fixed rule across the whole message. Break the rule and the sentence appears. Here, each letter has moved three places forward, and the text is "THE QUICK BROWN FOX".

The idea

A simple substitution cipher replaces each letter with a different one, and the same letter is always swapped for the same partner. There are about four hundred septillion possible keys, but the code falls to patient reasoning, because language leaves fingerprints.

How to solve one

• Short words first. A one-letter word is A or I. Two-letter words are limited to a few like OF, TO, IN, IT.
• Count letters. The commonest letter in the code probably stands for E.
• Look for THE and AND. A three-letter word that appears often is likely THE.
• Watch double letters. In English they are usually LL, EE, SS, OO or TT.
• Test and revise. Pencil in a guess, check it against every other word where those letters appear, and rub it out if it fails.

Poe made cryptograms a public fad in the 1840s, and "The Gold-Bug" uses frequency analysis to crack a pirate's cipher.

Why it matters to a writer or editor

A cryptogram is a fine exercise in how English is built. Solvers learn which letters and combinations are common, which sharpens the proofreader's eye. For a writer, a cipher is a ready plot device, and the cracking of one is an easy way to dramatise a character's cleverness. See also the anagram, which rearranges letters rather than replacing them, and the crossword.

Frequently asked questions

How do you solve a cryptogram?

Start with single-letter words, which are almost always A or I. Then look for the common three-letter word THE and for double letters. Pencil in guesses and test them against other words.

What is the most common letter in English?

E, followed by T, A, O, I, N, S, H and R. The most frequent letter in a cryptogram is often E.

Who solved cryptograms for fun?

Edgar Allan Poe popularised them with newspaper challenges in the 1840s and wrote the cipher story The Gold-Bug.