hi friends in pki, if someone obtains a servers public key and also if stoled the servers private key from that server, then he can decrypt data. right ? so then why we say pki is the best solution nowadays ? what is his advantage in this case ( stolen) in comparision with one-way hashing and symmetric encryption ? thanks

1) If someone steals you private key, that means you did a poor job of protecting it. Please research Hardware Security Modules (HSMs). With an HSM, nobody is going to "steal" your key. 2) one-way hashing is a signing method that *depends* on asymmetric encryption, so that the original signer of the data is able to securely send their encrypted hash value to the recipient, allowing the recipient to compare the hash value they generate with the hash value generated by the originator / sender. This is basic stuff you need to review. 3) Symmetric encryption involves key exchange. You need to securely get the symmetric key to the other person. Guess what is used to transport the symmetric key... Yep, asymmetric encryption again. Your question, honestly, does not make any sense, since the two technologies you bring up, both use asymmetric encryption Brian