Hash Code and Checksum - what's the difference?

Question

My understanding is that a hash code and checksum are similar things - a numeric value, computed for a block of data, that is relatively unique.

i.e. The pr

Answer 1

A checksum protects against accidental changes.

A cryptographic hash protects against a very motivated attacker.

When you send bits on the wire, it may accidentally happen that some bits are either flipped, or deleted, or inserted. To allow the receiver to detect (or sometimes correct) accidents like this, the sender uses a checksum.

But if you assume there is someone actively and intelligently modifying the message on the wire and you want to protect against this sort of attacker, then use a cryptographic hash (I am ignoring cryptographically signing the hash, or using a secondary channel or such, since the question does not seem to elude to this).