🎓 Ages 15–18 · Grades 9–12 · Cryptography

VaultForge

Every secret code has a logic you can reason your way into. Here you read a real scrambled message, predict what it says, and crack it — no jargon, no lectures, nothing sent anywhere. White-hat only: these are the historical ciphers that teach the math behind modern crypto.

The Cipher Lab ★ the main event

Read a real scrambled message — a Caesar shift, a Vigenère keyword, a frequency puzzle, the clock math behind a shift — predict what it says or which technique cracks it, then see the worked-out decryption and why the method works. A pure engine decrypts each one, so the answer is exact.

Open the Cipher Lab →

Who you’ll meet

Not mascots — everyday code-breakers, each one showing a single cryptography idea in action. You’ll run into them in the Cipher Lab.

  • Cassia — slides the alphabet a fixed number of places (the Caesar shift)
  • Freya — reverses a known shift to recover the message
  • Pax — finds the key from a single matched letter (breaking the shift)
  • Sela — cycles through a keyword so each letter shifts differently (Vigenère)
  • Hana — shows how a longer keyword hides letter patterns
  • Mox — counts letters to break a cipher — frequency analysis
  • Vesna — does the clock math behind every shift (modular arithmetic)
  • Kai — maps the most common letter back to E to find the key
  • Ivo — shows why a 25-key cipher can’t protect anything real
  • Sen — the mentor — sets a goal, cracks alongside you, guides reflection

Check what you know

Sixteen short kits — from "what is a cipher?" to substitution, Vigenère, frequency analysis, hashing, and public-key ideas — anchored to computer-science security standards. Hints when you want them; your progress stays on this device.

1. What Is Encryption? Encode vs encrypt; confidentiality · 25 questions 2. The Caesar Shift Shift cipher; the key · 25 questions 3. Substitution & Frequency Analysis Monoalphabetic substitution; frequency analysis · 25 questions 4. The Vigenère Cipher Polyalphabetic; keyword · 25 questions 5. Modular Arithmetic The clock math behind ciphers · 25 questions 6. Transposition Ciphers Reorder, don't replace · 25 questions 7. The Key & Kerckhoffs's Principle The key vs the algorithm · 25 questions 8. Symmetric vs Asymmetric Shared key vs key pair · 25 questions 9. The Public-Key Handshake Locked-box exchange; public/private keys · 25 questions 10. Hashing & Integrity One-way functions; fingerprints; integrity · 25 questions 11. Steganography Hidden in plain sight · 25 questions 12. Known-Plaintext & Crib Attacks Crib / pattern attacks · 25 questions 13. Passwords & Entropy Strength, entropy, reuse · 25 questions 14. Phishing & Social Engineering Recognize the fake (defensive) · 25 questions 15. Forensics Lite Find the flag in the data · 25 questions 16. Capture-the-Flag Capstone Multi-stage CTF · 25 questions

How it works

VaultForge is written to trust you — it’s about the reasoning, not memorizing terms, and a wrong prediction is just a place to learn. These are historical, breakable ciphers taught for understanding, never to defeat real security. Your progress is saved only on this device: no accounts, nothing sent anywhere.