See this page for information concerning RDP encryption...

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/termserv/termse
rv/remote_desktop_protocol.asp

Personally I run RDP through a Secure Shell (SSH) tunnel both for added
security and for easy access to multiple PCs on my home LAN. In my case I
use a 2048-bit RSA private/public key pair (encrypted with a strong pass
phrase) versus a password (strong or otherwise) for authentication.

http://theillustratednetwork.mvps.org/Ssh/RemoteDesktopSSH.html

You could do the same thing, ie. tunnel RDP, through a IPSec/L2TP or SSL VPN
if you wished.

Hi,

Yes.

The highest available encryption level is used by default, which amounts to
128-bit RC4.  There are some flaws with it -- plaintext checksums make a
cryptoanalysis attack potentially easier than it should be -- however, it's
still quite well encrypted and the keys are unique to each session.

The single layer of authentication (username and password only) is usually a
more serious problem.  For high security requirements, consider wraping RDP
access with a VPN and smart card or certificate authentication.

For personal use, make sure your Windows user accounts have decent
passwords.  If you only connect from certain locations (e.g. from the office
to your home computer) you can configure your firewall (or router, if there
is one) to only allow RDP connections from certain IP addresses or address
blocks.