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The app

Cryptolab

Classic ciphers, encoded and explained.

Long before passwords and keys, people hid messages with pen, paper and a little cleverness, and those methods are still the best way to understand how secret writing works. Type a message, pick a cipher, watch it transform as you type, then flip one switch to turn the secret back into plain text.

• CaesarShift the alphabet, or lay all twenty-six shifts out at once to crack one.
• VigenèreLock a message behind a keyword.
• AtbashFlip the alphabet end for end.
• Rail fenceWeave the letters along a zig-zag.
• A1Z26Turn words into plain numbers.

Seen properly

The visual codes, shown the way they are meant to be

Morse as dots and dashes you can flash across the screen, semaphore as little flag-waving figures, Braille as raised six-dot cells, tap code on its grid, each with a reference chart so you can read them anywhere.

Every cipher carries a short "how it works" page in plain language and a small animated example — the Caesar ring turning, the rail fence zig-zagging into place — so you are never only pushing buttons. Challenges then ask you to decode a message, spot which cipher was used, or encode a word to a target, keeping your best score. Anything worth keeping is saved with its settings and decoded again later.

Choose an accent theme, set the Morse flash speed, switch between English and Norwegian, and tinker away completely offline: no account, no ads, nothing leaving the device.

Package com.glyphworks.cryptolab

Play ciphers, not real secrets. Everything here was broken long before computers existed: a Caesar falls in seconds and a Vigenère in minutes. Cryptolab is a teaching lab, so never use it for anything that actually needs protecting — passwords, documents, messages that matter. For those, use the encryption already built into your phone and your messaging app, and treat any app that offers you a hand-made cipher for real data as a warning sign.

Working out

Why a cipher with 10²⁶ keys still falls

A simple substitution has 26! keys — 403 291 461 126 605 635 584 000 000 of them — and a billion guesses a second would take about 12.8 billion years, roughly the age of the universe. Nobody breaks it that way. They break it because English is repetitive, and Claude Shannon put a number on exactly when that becomes fatal: the unicity distance, the key's entropy divided by the redundancy of the language, about 3.2 bits a letter.

Below the unicity distance several keys still give sensible text and a message is genuinely ambiguous; above it, exactly one reading survives and the work is only arithmetic. A Caesar passes that point after one and a half letters. A Vigenère with a five-letter keyword needs seven. Even full substitution, with its 88 bits of key, gives up at about twenty-eight letters — which is why a paragraph in any of these ciphers has precisely one answer, and always did.

What's not here: no encoder, no decoder, no charts and no challenges. This page types nothing and solves nothing; it only measures how long a message has to be before its solution stops being a matter of opinion. The lab itself is the app.