extract preshared key from config file

Dear fortinet specialists, does anybody know how to extract an encrypted preshared key from config file? The psk in our environment isn' t anywhere to be found. To avoid a completely new ipsec configuration on all devices it would be better to get the key via config file. However, the FortiClient VPN Tool creates a config file with an encryped psk inside. The same happens by saving config of the FG device. Up to now it was possible to use the FortiClient config files to get new Windows devices working. Now there' s in iPad i want to get working and so i have to enter all config data manually. Regards, Christian