Hashes and encryption

Encryption can be undone with a key. A hash cannot be undone at all.

Hashes

A hash turns any input into a short fixed-size fingerprint. The same input always gives the same fingerprint, and a tiny change gives a completely different one. Sites use hashes to check that a file was not changed.

$ echo -n hello | sha256sum
2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824

Encryption

Encryption scrambles data so only someone with the key can read it. Keys, not secrecy of the method, protect the data.

Try it

Hash the word ctf, then ctF. Compare the two results.