A
digital code that can be attached to an electronically transmitted message that uniquely identifies the sender. Like a written signature, the purpose of a digital signature is to guarantee that the individual sending the message really is who he or she claims to be. Digital signatures are especially important for
electronic commerce and are a key component of most
authentication schemes. To be effective, digital signatures must be unforgeable. There are a number of different
encryption techniques to guarantee this level of security.