Chapter 6 Deploying Wireless Networks for FortiOS 5.0 : Protecting the WiFi Network : WiFi data channel encryption : Configuring encryption on the FortiAP unit
  
Configuring encryption on the FortiAP unit
The FortiAP unit has its own settings for data channel encryption.
Enabling CAPWAP encryption - FortiAP web-based manager
1 On the System Information page, in WTP Configuration > AC Data Channel Security, select one of:
Clear Text
DTLS Enabled
Clear Text or DTLS Enabled (default)
2 Select Apply.
Enabling encryption - FortiAP CLI
You can set the data channel encryption using the AC_DATA_CHAN_SEC variable: 0 is Clear Text, 1 is DTLS Enabled, 2 (the default) is Clear Text or DTLS Enabled.
For example, to set security to DTLS and then save the setting, enter
cfg -a AC_DATA_CHAN_SEC=1
cfg -c