UNCONDITIONALLY-SECURE DIGITAL-SIGNATURES

All known digital signature schemes can be forged by anyone having enough computing power. For a finite set of participants, we can overcome this weakness. We present a polynomial time protocol in which a participant can convince (with an exponentially small error probability) any other participant that his signature is valid. Moreover, such a convinced participant can convince any other participant of the signature's validity, without interaction with the original signer. An extension allows, in most cases, a participant who receives a signature from any source to convince each other participant of its validity. If a participant cannot use the signature to convince others, he knows so when he receives it.