signature in pre_inspection and client_data payload

Hi,

I would like to enable the openconnect client to connect to my corporate firewall. Currently I'm using the f5fpc client which is somewhat limited.

I've figured out most of the protocol, but I'm stuck with populating the signature field in the payload that is (initially) passed to my.logon.php3 (and consequentally) to my.activation.php3.

Anyone who can shine a light on this or can point me to documentation or specification?

Thanks!

Regards,

Mark