can't say , what exactly you're asking because The purpose of Digital signature is 'Integrity'. It's like in your college some important notice is attached to notice board , now how would you know that it's not a garbage message but a True notice? by seeing your HOD's signature on paper , you would make sure that it's a valid notice. SO i mean here Signature is protector which is nothing but private key of HOD ( Nobody can make HOD's sign) Everyone have knowledge how HOD's signature looks like(means everyone has public key of HOD, sender), so everyone can confirm that notice is issued by HOD.
So in this all procedure , here is every sender will sign document by his own private key and receiver will verify by sender's public key..and everyone has only one kind of signature , how many kinds of signature do you possess? only one i hope.
