Glossary
Hash
16/04/2026
A hash is a fixed-length string of characters produced by a hash function — a mathematical algorithm that takes any input data and outputs a deterministic, fixed-size digest. Even a tiny change to the input produces a completely different output.
Properties of cryptographic hash functions
- Deterministic — the same input always produces the same output
- Fixed-length output — regardless of input size (e.g., SHA-256 always outputs 256 bits)
- One-way — it is computationally infeasible to reverse the hash back to the input
- Avalanche effect — changing even one bit in the input changes ~50% of the output bits
- Collision-resistant — it is infeasible to find two different inputs with the same hash
Hash functions in cryptocurrency
| Use case | Hash function | Where |
|---|---|---|
| Block hashing / mining | SHA-256 | Bitcoin |
| Block hashing / mining | Ethash / Etchash | Ethereum Classic |
| Transaction ID | SHA-256d | Bitcoin |
| Address derivation | RIPEMD-160, Keccak-256 | Bitcoin, Ethereum |
Hashing in mining
Mining is essentially a hash-guessing contest. Miners repeatedly hash a block header (with a changing nonce) until the result falls below the difficulty target. The speed at which a miner can compute hashes is called hashrate.
