The key difference here is one between a message authentication code [1] and digital signature [2]. A digital signature uses public key cryptography: one perso

The key difference here is one between a message authentication code [1] and digital signature [2]. A digital signature uses public key cryptography: one person can generate and sign messages, everyone else can verify. A common one is the DSA[3] -- but there are many others, including freakishly fast elliptical curve versions. [1] http://en.wikipedia.org/wiki/Message_authentication_code http://en.wikipedia.org/wiki/Message_authentication_code [2] http://en.wikipedia.org/wiki/Digital_signature http://en.wikipedia.org/wiki/Digital_signature [3] http://en.wikipedia.org/wiki/Digital_Signature_Algorithm http://en.wikipedia.org/wiki/Digital_Signature_Algorithm