Learn Cryptography: Encryption

Learn cryptography by doing it. Encrypt a message with a Caesar cipher, watch frequency analysis break it, then work your way up to Vigenère, AES, RSA and public key encryption. Every idea comes with a tool you can touch: a cipher decoder, a working Enigma machine simulator, a hash lab and a daily cryptogram to crack.

This is a cryptography and cryptology course, not a crypto-trading app. You learn how encryption really works, and how codebreakers attack it.

WHAT YOU'LL LEARN
• 67 courses and 261 bite-sized lessons, from complete beginner to expert level
• Classical codes and ciphers: Caesar, substitution, Vigenère, Playfair, transposition and the one-time pad
• Cryptanalysis: frequency analysis, brute force and why each one falls
• Hash functions (MD5, SHA-1, SHA-256), salts and password hashing with bcrypt and Argon2
• Symmetric encryption: AES, block cipher modes, stream ciphers and ChaCha20
• Public key cryptography: RSA, Diffie-Hellman, elliptic curves and digital signatures
• Encryption in the real world: TLS/HTTPS, certificates and PKI, SSH, VPNs, JWT and OAuth
• Advanced topics: zero-knowledge proofs, homomorphic encryption and post-quantum cryptography

HANDS-ON TOOLS
• Cipher Bench: a decoder and encoder for 17 ciphers and encodings. Caesar, Atbash, ROT13, Base64, hex, binary and Morse code are free. Vigenère, Autokey, Beaufort, Affine, Playfair, Rail Fence, Columnar, Scytale, substitution and XOR come with Pro.
• Crack Lab: a codebreaker's workbench with a letter frequency chart, bigrams and a brute force of all 26 Caesar shifts. Kasiski key-length search and the auto-solver come with Pro.
• Enigma: an Enigma machine simulator wired like the real one. Rotors I-III and reflector B are free; rotors IV and V, reflector C and the plugboard come with Pro.
• Hash Lab: type anything and see its SHA-256 hash, and test how long a password would survive. MD5, SHA-1, CRC32, the avalanche effect and HMAC come with Pro.
• Public-Key Lab (Pro): see how two strangers agree on a secret in the open.
• Secret Message: encrypt a note and send it as a link. Nothing is stored anywhere.

DAILY PUZZLES AND COMPETITION
• Daily Cipher: one cryptogram a day (a cryptoquote from a famous quotation), the same one for everybody, with its own leaderboard
• Cipher Duel: one ciphertext for everyone each week. Race the clock and climb the ladder
• Codebreaker League: a weekly league ranked by the XP you actually earned
• Streaks, XP and progress tracking to keep you consistent

PRACTICE AND PROVE IT
• 60 Python coding missions: implement Caesar, Atbash, substitution, SHA-256, RSA and more (2 free, the rest with Pro)
• Quizzes, flashcard review and a cryptography cheat sheet
• 50 cryptography interview questions with answers
• Codebreaker Certification: a timed practical exam. Break a Caesar with no key, run a Vigenère, name an algorithm family and earn a certificate you can share (Pro, or with credits)
• AI Mentor: stuck on a concept? Ask and get a clear answer. One free question a day

WHO IT'S FOR
• Beginners who love secret codes and want to know how they work
• Students taking a cryptography, cryptology or cyber security class
• Developers who need to use encryption, hashing and TLS correctly
• Puzzle fans who enjoy cryptograms and codebreaking

FREE TO START
The first course, the Daily Cipher, the weekly Cipher Duel, the Codebreaker League, Secret Message and the free parts of the Cipher Bench, Crack Lab, Enigma and Hash Lab cost nothing. Pro unlocks every course, the full toolset and more AI Mentor, and removes ads.

Available in 22 languages.

Download Learn Cryptography: Encryption and crack your first code today.