Hash

A hash is the output of a hash function, which takes input data of any size and produces a fixed-length string of characters. In cryptocurrency, hash functions are fundamental to blockchain security and transaction verification.

Key properties of cryptographic hash functions:

Deterministic: The same input always produces the same output

One-way: It's computationally infeasible to reverse a hash back to its original input

Collision-resistant: It's extremely difficult to find two different inputs that produce the same hash

Avalanche effect: A tiny change in input produces a completely different hash

Common hash algorithms in crypto: - SHA-256: Used by Bitcoin (produces 256-bit hashes) - Keccak-256: Used by Ethereum - RIPEMD-160: Used in Bitcoin addresses

Hashes are used for: - Linking blocks in a blockchain (each block contains the previous block's hash) - Mining and proof-of-work - Creating wallet addresses - Verifying transaction integrity - Merkle trees for efficient data verification

Example: The SHA-256 hash of "hello" is "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"