Cryptography
Classical ciphers, hashes, key exchange and modern symmetric algorithms. Type your own input and watch what each one does to it.
- Lessons
- 32
- With simulators
- 13
Classical5
- Caesar cipherIntroShift every letter by a fixed amount, then break it by counting letters.Simulator
- Playfair cipherIntroEncrypt letter pairs using a 5 by 5 keyed grid.Simulator
- Vigenère cipherIntroA repeating keyword picks a different shift for each letter.Simulator
- Rail fence cipherIntroWrite the message in a zigzag, then read it off row by row.Simulator
- Hill cipherCoreEncrypt blocks of letters with matrix multiplication.Simulator
Hash9
- SHA-256CoreTurn any input into a 256-bit fingerprint, and see how a one-letter change spreads.Simulator
- SHA-3CoreThe Keccak sponge hash, standardised as an alternative to SHA-2.
- bcryptCoreA deliberately slow hash for storing passwords.
- PBKDF2CoreStretch a password into a key by repeating a hash many times.
- BLAKE3CoreA fast, parallel hash built on a Merkle tree.
- MD5IntroA broken hash that is still everywhere. See why collisions matter.
- RIPEMD-160CoreThe 160-bit hash behind many Bitcoin addresses.
- CRC32IntroA checksum that catches accidents but not attackers.
- MurmurHashCoreA fast non-cryptographic hash for hash tables.
Key exchange7
- Diffie-HellmanCoreAgree on a shared secret over a channel anyone can read.Simulator
- ECDHAdvancedDiffie-Hellman on elliptic curves, with much smaller keys.
- IKEAdvancedHow VPN endpoints negotiate keys before they send traffic.
- X3DHAdvancedThe handshake that lets secure messengers start a chat while you are offline.
- PAKEAdvancedProve you know a password without sending it.
- SIDHAdvancedA post-quantum key exchange that was broken in 2022.
- CRYSTALS-KyberAdvancedThe lattice-based key exchange standardised for the post-quantum era.
Symmetric11
- AESCoreThe block cipher that protects most of the internet. Try every mode.
- DESCoreThe 1970s standard, and why its 56-bit key could not last.Simulator
- Triple DESCoreRun DES three times to stretch its life.
- BlowfishCoreA fast block cipher with a key-dependent S-box.
- TwofishCoreBlowfish's successor and an AES finalist.
- ChaCha20CoreA stream cipher built from add, rotate and xor.Simulator
- Salsa20CoreThe stream cipher ChaCha20 grew out of.Simulator
- RC4CoreA once-popular stream cipher and the flaws that ended it.
- PRESENTAdvancedAn ultra-light block cipher for tiny devices.Simulator
- SpeckAdvancedA lightweight cipher designed for software on small hardware.Simulator
- SimonAdvancedSpeck's hardware-oriented sibling.Simulator
Asymmetric8
- RSAPlanned
- ECCPlanned
- ElGamalPlanned
- DSAPlanned
- PaillierPlanned
- NTRUPlanned
- LUCPlanned
- McEliecePlanned