Cyclone V, Security, key, eFuse, microscope, (descrambled?)

Hi,

I’m trying to dig into the security features of a Cyclone V.

Assuming it is worth to decap and delayer the device to have a look at the eFuses with a microscope – even in 28nm.

Can then the key be extracted, even if it is presumable descrambled?

A relevant answer is highly appreciated.

Thanks in advance.

Regards