If Alice and Bob each know their own private key and the other's public key, they can communicate securely, through any number of public key based protocols such as IPSec, PGP, S/MIME, or SSL. However, how do they know each other's public keys? The
sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target