Bitcoin & Money

Cryptography

Hash functions, keys, signatures and the elliptic curves that underpin Bitcoin.

  1. 1 The cryptographer’s toolkit The handful of building blocks — hashes, keys, signatures — that everything else is assembled from.
  2. 2 Hash functions Interactive The one-way digital fingerprint — try it live.
  3. 3 Salt Why the same password hashes differently for everyone — and how sites store passwords safely.
  4. 4 Key stretching Salt stops the lookup table; deliberately slow hashing stops the brute force that comes next.
  5. 5 HMAC A hash plus a shared secret — a tamper-proof seal proving a message is genuine.
  6. 6 Random numbers Unpredictable randomness is the raw material of every key — and computers are bad at it.
  7. 7 Private & public keys Interactive A secret you keep, a name you can share.
  8. 8 Digital signatures Interactive Prove you authorised something, without revealing your secret.
  9. 9 Encryption & decryption Scrambling messages — and why Bitcoin barely uses it.
  10. 10 RSA Interactive The first public-key system to go mainstream — and why its keys keep getting bigger.
  11. 11 Elliptic curves Interactive The trapdoor maths linking your public and private keys.