In this blog you will see a simple PPK deployment to ensure PSK are not crackable.
1st PPK is a IKEv2 feature
2nd you can make it option or mandatory in the fortios . This allows for a simple PSK and the choice of enforcing PPK
here's the fgt1 cfg
the 2nd fgt is exactly the same in this the fgt1 is a dynamic-ipsec peer
To verify PPK was used run the "diag vpn ike gateway" cmd from cli
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