VNC User Guide - RealVNC

Chapter 7: Making Connections Secure
• Tighten the encryption rules by increasing the AES key size to 256-bit. This makes connections ultrasecure,
but may impact performance slightly. It also means only VNC Viewer 4.6 or later can connect.
For VNC Server (Personal), you can just relax the encryption rules. 256-bit AES encryption is not available.
Upgrade the host computer to VNC Server (Enterprise) if security is important to you.
Note: A connecting user can request that the encryption rules be tightened, but not relaxed.
To change the rules, open the VNC Server - Options dialog. More on this dialog. On the Connections tab,
select an alternative to the default Always on option from the Encryption dropdown:
Choose:
• Always maximum to specify 256-bit AES. Note that only VNC Viewer 4.6 or later can connect. A
connecting user cannot request that encryption be turned off, or the AES key size reduced to 128-bit.
• Prefer on to prefer, though not mandate, that connections be encrypted using 128-bit AES. A
connecting user can either request that encryption be turned off (by selecting Prefer off in the VNC
Viewer dialog), or the AES key size be increased to 256-bit (by selecting Always maximum in the VNC
Viewer dialog).
• Prefer off to prefer, though not mandate, that connections be unencrypted. Choose this option to
allow older versions of VNC Viewer, or VNC-compatible Viewer technology, to connect. A connecting
user can request that encryption be turned back on, either to 128-bit AES (by selecting Prefer on or
Always on in the VNC Viewer dialog), or to 256-bit AES (by selecting Always maximum in the VNC
Viewer dialog).
For more information about requesting encryption in the VNC Viewer dialog, see Step 4: Request an
encrypted connection on page 22.
110 VNC User Guide