The ProxySG appliance at the branch office uses the ProxySG appliance at the data center as its forwarding host, allowing SSL Proxy functionality to be enabled on both appliances.
Setting Up SSL Proxy Chaining Functionality
Note that this applies to intercepted SSL connections only. For tunneled SSL connections the data center proxy appliance sees the original server certificate.
Now, when an SSL connection is intercepted at the branch proxy appliance, the ProxySG appliance emulates the server certificate and presents the emulated server certificate to the data center proxy appliance.