Change one character and watch half the digest move. Then edit a record inside a chain and watch the break propagate.
A fingerprint, not a lock
A hash is a fixed-length fingerprint of data. Change one byte and the fingerprint changes completely.
It does not encrypt, hide, or protect anything — it detects change. People consistently expect a
small change to produce a small change in the digest. Measure it.
Now chain them
Each record carries the digest of the record before it. Altering record k leaves every record from
k onward pointing at a digest that no longer matches. Edit any record below.