Comments by AlanC12 (Top 2 by date)

Don't think I made myself clear in the question, sorry. I am set up the way you suggested (each client has its own key pair, server having a copy of public key for each client). Perhaps I can explain it with an email example.

Bob Sends Alice an email. Bob signs a hash of his message using his private key. Alice can now verify for certain the email came from Bob because she can verify the signed hash using Bob's public key.

My question - could somebody else (say Fred) sign a nessage with Bob's public key and send it to Alice, making Alice think the message came from Bob, when actually it came from Fred? Or is it not possible to sign a message with the public key?