Like word games? Try using the English language to crack codes

Illustration of a magnifying glass hovering over a key lock, magnifying the letters "ETAOIN SHRDLU" with cryptographic codes in the background.
Aishwarya Jayadeep/Senior Staff

Related Posts

If you’re one for solving crossword puzzles and word searches in your daily newspaper or on your phone app, here’s another wordy puzzle you should try: cryptograms!

Originally used for military and personal secrets, cryptograms are puzzles that contain a short piece of text encrypted by a cipher. These ciphers are normally simple enough to solve by hand. The most frequently used one is the monoalphabetic substitution cipher, in which each letter of the original text is substituted with a different letter or character. Here’s a short guide on how to crack one of these monoalphabetic codes using trends in the English language.

Letter frequencies

Within your encrypted text, a certain letter might appear more frequently than other letters. Each occurrence of this letter will trace back to a single letter of the original text, but how do we figure out what this original letter is? Letter frequency is the number of times letters of the alphabet appear, on average, in a written language. In the English language, the nonsense phrase “ETAOIN SHRDLU” represents the 12 most commonly used letters in descending order. Therefore, these letters are distributed in such a way that they remain the most frequent in almost any sample of English text, though it may not be exactly in the same order. The remaining 14 are just as necessary to crack the entire code, but using this knowledge of letter frequency, you will likely be able to guess the remaining letters after solving for the most frequent ones.

Word length

The length of each individual word in the entirety of your encrypted text may hint you toward what the word itself may be, which may make matching letters easier. For example, if the encrypted word is a single letter, it may translate to the words “I” (the pronoun) or “a” (the indefinite article). Two-letter encryptions may translate to words such as “to,” “of,” “is” and “it.” With encryptions that consist of three or more letters, decoding gets trickier, but you can refer to this list to see the most frequently used words in the English language and their letter counts.

Punctuation

Although the letters change within a cryptogram, the punctuation remains the same. Therefore, you can observe punctuation marks to figure out what words surround it. Apostrophes indicate that the word is either a contraction, such as “can’t,” “don’t” and “wasn’t,” or a possessive noun, where an “ ’s” or “s’ ” is used. Commas can pinpoint you in the right direction depending on their location within a sentence. If a comma is found near the beginning of a sentence following one to three words, then the words are likely transitional expressions such as “therefore,” “after all” and “furthermore.” If a single comma is found in the middle of a sentence, the word following is probably a conjunction (and, or, but). While there are more punctuation marks that can hint at different terms and expressions, the apostrophe and comma are, in my opinion, the most insightful for solving cryptograms.

Up for the challenge? Try to crack a few cryptograms here! With these tricks and rounds of practice, you’ll be a decoding pro in no time!

Contact Annie Lin at [email protected].