How Cipherday works
Cipherday is a free daily code-breaking game. Each day everyone in the world gets the same chain of three classic ciphers, escalating in difficulty, that hide a short public-domain quote — a proverb, an ancient saying, or a line from a long-out-of-copyright author. You crack each stage in your browser, watch the final layer decrypt character by character into the day’s quote, and get a clean, spoiler-free card showing your time. No account, no cost, and the answer is never spoiled for the friend you share it with.
A quick cipher primer
Caesar shift (stage one, warm-up). Every letter slides the same number of places down the alphabet — shift by three and A becomes D. To break it you simply turn the shift dial until real words appear. There are only twenty-five shifts to try.
Keyword substitution (stage two, medium). Each letter is swapped for a fixed partner, so the alphabet is scrambled but consistent. Tap a ciphertext letter and assign it a plaintext letter; every copy changes at once. Because the swaps are fixed, letter frequency and short common words give you a foothold.
Vigenère (stage three, the reveal). A repeating keyword shifts each letter by a different amount, so the same letter can encrypt two different ways — which is exactly what makes it harder. Type your best guess for the keyword into the key cells and the line re-resolves live until it clicks into the day’s marquee quote.
Rail-fence (stage three, some days). On some days the final cipher is a rail-fence instead of Vigenère: the letters are written in a zig-zag down and across a number of rails, then read row by row. Set the rail count on the dial and the line re-weaves live until the words fall back into order.
How to play
- Open today’s chain and start on stage one — the Caesar warm-up.
- Work the on-screen control until the live preview reads as genuine English.
- The stage clears itself the moment your text matches — there is no wrong-guess penalty.
- Climb through substitution and the final cipher — Vigenère, or a rail-fence on some days; the final crack triggers the decryption cascade.
- Share your spoiler-free card, keep your streak, or forge a cipher of your own.
Tips for cracking faster
- In English, E and T are the most common letters — match them to the most frequent cipher letters first.
- Short words matter: a lone letter is almost always A or I; common three-letter words are “the” and “and”.
- Double letters in the ciphertext often map to LL, EE, SS, or OO.
- For Vigenère, the key-length hint is the biggest shortcut — get the length, then guess a familiar word of that size.
- On a rail-fence day the message is reordered, not re-lettered — the same letters appear, just scrambled. Try each rail count from three upward and watch for the first word to snap into place.
- Hints are always there if you get stuck, but a no-hints crack is the badge worth chasing.
- Speed comes with pattern recognition — play a few days in a row and the shapes start jumping out.
FAQ
Is it the same puzzle for everyone? Yes. The chain is generated from the UTC date, so every player faces the identical puzzle each day — that is what makes “faster than X% today” fair.
Do I need an account? No. Your streak and best time are stored only in your own browser.
Where do the quotes come from? A curated bank of public-domain lines — traditional proverbs, ancient and classical sayings, and pre-1929 authors. Nothing modern or copyrighted.
What if I can’t finish? You can’t lose. Reveal hints as needed, or replay past days from the archive.
Does sharing spoil the answer? Never. Your card shows your time and which ciphers you cracked — not the quote.