Hash function
a.k.a. Hash, Hashing
A one-way blender for data: any input goes in, a fixed-length fingerprint comes out, and you can't run it…
In plain English
A one-way blender for data: any input goes in, a fixed-length fingerprint comes out, and you can't run it backwards.
A hash function takes any data, a word or a whole block of transactions, and grinds it into a short fixed-length string called a hash. Change a single comma in the input and the output changes completely.
Blockchains lean on this everywhere. Each block carries the hash of the one before it, so tampering with old history breaks every fingerprint after it. Bitcoin's proof of work is a race to find a hash that meets a target.
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