How Tampering Changes the Digest
A hash function computes a fixed-length digest from any message. Even a single-character change to the message alters the computed digest, so comparing it against the digest from signing time reveals tampering. A digital signature is this digest encrypted with the private key.
GOAL
Explain how a hash function detects tampering, and how a digital signature makes use of it.
When the message gets tampered with, what happens to the signature verification result?