A cryptographic hash maps input data to a fixed-size output. Useful properties make it difficult to reverse or deliberately find colliding inputs. Changing the input usually changes the output dramatically.
Hashing differs from encryption. A public hash is not permission to spend funds and does not reveal a signing key. Blockchains use hashes in several structures, but a hash alone does not establish that the original input was truthful.
Worked example
A downloaded file can be checked against a trusted published hash. Matching hashes support that it is the same file, not that the file is safe or accurate.
Check your understanding
Is hashing a way to recover the original message later?
Show explanation
No. It is designed as a one-way transformation, unlike reversible encryption.
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