How to Solve Cryptograms: Substitution Cipher Techniques

A cryptogram is a message where every letter has been swapped for another. In the Cryptogram Vault you get help: words hidden in a letter grid reveal parts of the key. But the real skill is filling in the rest yourself. These are the techniques code-breakers have used for centuries, adapted for the Vault.

How a substitution cipher works

In a simple substitution cipher, each plain letter is always replaced by the same cipher letter. If E becomes H once, every E in the message is an H. That consistency is the weakness you exploit: patterns in the plain text survive encryption.

Technique 1: Use the keys you find

In the Vault, every hidden word you trace in the grid unlocks the cipher mapping for its letters. Find words first, because each one may reveal several letters at once. But don’t feel you must find them all. Once enough of the passcode is readable, you can usually guess the rest.

Technique 2: Letter frequency

In normal English, a few letters do most of the work. Across the words in Cipher Siege’s puzzles, the letters that appear in the most words are:

So the cipher letter that appears most often in a long message is a strong candidate for E. Frequency works best on longer texts. On a single short word it can mislead, so use it as a starting guess, not a rule.

Technique 3: Pattern words

Look at the shape of each encrypted word. Repeated cipher letters must be repeated plain letters, at the same positions. A 4-letter cipher word shaped like ABBA must be a word like “noon” or “deed”. A word shaped ABCA, such as “that”, is a giveaway in longer messages.

Short words are the easiest patterns of all. In English messages, one-letter words are almost always A or I, and the most common three-letter word is “the”. If the same three-letter cipher word appears several times, try THE first.

Technique 4: Endings

Endings are frequent and predictable. In 7-letter words, -ED ends 13.5% of answers and -ING ends 11.1%. If a cipher word ends in a three-letter group you have seen elsewhere, test -ING, -ION, -ERS or -EST against your known mappings.

Technique 5: Keep a key table

Every confirmed mapping helps everywhere else in the message. The Vault shows auto-mapped letters from keys you’ve found; fill in the rest as you deduce them. Two rules keep you honest:

• No two cipher letters can map to the same plain letter.
• If a guess creates an impossible word anywhere else, undo it.

A worked example

Say the passcode is six cipher letters, Q M X W N R, and your keys have revealed Q→C, X→S, W→T and R→E. You can now read C _ S T _ E. Six letters, C at the start, STE in the middle and E at the end: CASTLE fits, so M→A and N→L. Two unknown letters, solved by pattern alone, and those two new mappings will help with any other words in the vault.

Where to start on a new vault

1. Scan the grid for any word you can see at a glance and trace it. Free keys are the fastest progress.
2. Fill in every revealed mapping across the whole passcode.
3. Look for the cipher word with the fewest unknowns and solve it by pattern.
4. Repeat. Each solved word adds mappings that make the next one easier.

This loop of keys, then patterns, then more keys is how professional cryptographers worked through historical ciphers by hand. The Vault simply hands you a few of the keys to get started.

Common mistakes

• Assuming a letter maps to itself. In most ciphers no letter stays the same, so don’t assume an H in the cipher is an H in the answer.
• Chasing every key. Keys are a shortcut, not the goal. If you can read the passcode, type it.
• Ignoring short words. They are the fastest way in. Solve them first.