checksum
termnetworkingprogramming
A small value computed from data so a receiver can notice accidental corruption - detection, not correction, and not protection.
It defends against noise, not against people: an attacker who changes the data simply recomputes the checksum. That is the distinction from a signature or a message authentication code, and confusing them is a real design error rather than a pedantic one. Operationally the surprise is offload - network cards compute checksums in hardware, so a capture taken on the sending host routinely shows them as invalid, which is correct behaviour that has cost many hours of investigation.
Also known as: crc, fcs