Encryption won't do you any good - encrypted messages can be forged. But let's say you meant a signature or other form of authentication. That still does you n

Encryption won't do you any good - encrypted messages can be forged. But let's say you meant a signature or other form of authentication. That still does you no good if you're, say, a server getting data from a client. Very few servers want to allow clients to execute arbitrary code inside them. That still leaves some situations where it can be used - but it's a major limitation on the scope of those situations.