IPsec Protocol

The IPsec protocol itself is considered secure, there doesn't seem to be a better supported or more secure protocol that would meet all these requirements. As all the data which flows over the network is encrypted with strong algorithms, and the certificate method is considered secure, eavesdropping of the line should not easily be possible. Physical security is important, though, as the certificates are stored on the client machines. With the certificate in the bad man's hands, eavesdropping is definitely possible.