Forgery (MAC)
From Wikipedia, the free encyclopedia
In a digital signature or Message Authentication Code (MAC) system, an Selective forgery is the creation (by an adversary) of chosen message m and a valid signature (or MAC) σ for m, where m has not been signed or MACed in the past by the legitimate signer/MAC generator.
Universal forgery is a type of forgery, in a digital signature or Message Authentication Code (MAC) system, where an adversary has been able to find a tag t for every (given) message m.