Cipher Lock
Drag the vault dial or tap the arrow buttons to turn it, then tap Open vault. Desktop: left and right arrows turn, Enter opens, L shows the letter count.
What is Cipher Lock?
Cipher Lock is a free code-breaking game built around the Caesar cipher, a method roughly two thousand years old in which every letter is moved the same number of places along the alphabet. You already know the rule; what you do not know is how far the letters moved, and that number is the key. You turn a dial until the scrambled message turns back into English, using the fact that E is the most common letter in the language - a technique called frequency analysis.
How to play Cipher Lock
Controls: Drag the vault dial or tap the arrow buttons to turn it, then tap Open vault. Desktop: left and right arrows turn, Enter opens, L shows the letter count.
- 1Every letter of the intercepted note was moved the same number of places along the alphabet. That number is the key.
- 2Turn the vault dial by dragging it or tapping the arrow buttons. The brass ring shows the code letters and the steel ring under it shows what each one really means.
- 3Read the blue writing under the note - it decodes live as you turn. When it turns into real English, tap Open vault.
- 4Stuck? Tap Letter count. E is the most common letter in English, so turn until the glowing E sits under the busiest code letter.
- 5Crack all 5 vaults. Decoder starts with short notes and small keys; Codebreaker uses long messages and any key. Fewer wrong tries scores more.
Cipher Lock tips and strategy
- Start from the hint. If X is the most common letter in the code it is very probably a shifted E, and lining those two up usually solves it in one move.
- Watch the one and two letter words. A single letter is almost always A or I, and a two letter word decoding to something like 'qe' tells you instantly that the shift is wrong.
- Look for THE. It is the most common word in English, so a three letter word at the start of a sentence is a strong anchor.
- If nothing else works, just walk the dial through all twenty-six positions. That it only takes a few seconds is exactly the weakness this cipher has.
Cipher Lock FAQ
What is a Caesar cipher?
A cipher that replaces every letter with the one a fixed number of places further along the alphabet, wrapping round at Z. With a shift of three, A becomes D and cat becomes fdw. It is named after Julius Caesar, who is reported to have used it for military messages.
How do you break a Caesar cipher?
Two ways, and both are fast. You can try all twenty-six shifts, since one of them must be right, or you can use frequency analysis: find the most common letter in the coded message, assume it stands for E, and the shift falls straight out.
What is frequency analysis?
Using how often letters appear to work out what they stand for. In English E is the most common letter, followed by T and A, and that pattern survives any simple letter-for-letter substitution - which is what makes every cipher of this kind breakable without knowing the key.
Why isn't this cipher used today?
Because it has only twenty-six possible keys, and a computer can try all of them in less time than it takes to blink. Modern encryption uses keys with more possible values than there are atoms in the observable universe, so trying them all is not merely slow but physically impossible.
