As described elsewhere in these FAQ's, EchoVNC allows
two VNC users to connect with each other regardless of
firewall or router configurations on either side.

In addition to making VNC "firewall friendly", EchoVNC can
be used to securely encrypt the VNC data connections. To
activate this feature, simply place the "libeay32.dll" file from
the OpenSSL package into the EchoVNC installation directory.
That will activate end-to-end 128-bit AES encryption of the 
VNC data.