Cipher Bench

Cipher Bench turns cryptography into something you actually do rather than read about. It walks through a range of classic ciphers — Caesar shift, substitution, Vigenère, rail fence, Atbash, and up to a simplified RSA that demonstrates real public-key math with small primes — and for each one you can type a message, watch it transform character by character, and reverse the process to decode. Every cipher comes with a live view of what's happening under the hood: the Caesar wheel rotating, the Vigenère key repeating across the plaintext, RSA's key generation and modular exponentiation laid out step by step, so the mechanism is visible instead of hidden behind a single "encrypt" button.

Beyond encoding, Cipher Bench has a proper cracking side. A codebreaker workbench gives you real tools — a frequency-analysis chart that counts letter distribution in ciphertext, a brute-force sweep that runs every Caesar shift so you can spot the readable one, and an interactive substitution grid where you swap letters and watch the plaintext resolve as you narrow it down. A set of challenge puzzles hands you an encrypted message with no key and asks you to break it, rewarding the actual detective work of pattern-spotting rather than just handing over the answer.

The app is built as a full multi-screen tool — a cipher library, an encode/decode workbench per cipher, a codebreaker analysis screen, and a challenge browser that tracks which puzzles you've solved — with everything stored locally on the device. No account, no ads, no connection required; all the math runs on your phone.