Hashing and security · 1/2
The fingerprint machine
A hash function takes any input, a word, a file, an entire block of transactions, and produces a short fixed-length fingerprint. The same input always gives the same output, but change even one letter and the output changes completely.
SHA-256, used by Bitcoin, turns anything into 64 hexadecimal characters. You cannot work backwards from a hash to the original input, which makes it a one-way function.