opencrypto
Break a toy cipher, then fix it, and see why keys matter, in three sessions.
- Session 1: A secret message: the Caesar shift cipher (Level 1, 60 min)
- Session 2: The key space, frequency analysis and Vigenere (Level 2, 75 min)
- Session 3: Perfect secrecy, hashes, HMAC and key size (Level 3, 90 min)