Why wouldn't you have your enclave carry a certificate instead of doing this?
You may eventually need to rotate its identity key, and if you want to do that, you need a certificate system.
You may eventually need to rotate its identity key, and if you want to do that, you need a certificate system.
A certificate is also a secret + certified public key, right? So, if you cannot store the certification on the TKey (no persistence) than you're left with the same construction. Right now, I'm skipping the complexity of certs (PKCS11, IIRC) etc. The identity being persistent is in order to authenticate the device.
If this is for anyone but yourself, you're going to need a certificate chain. An FPGA like the TKey can also store a significant amount of data in a ROM and you should have no problem storing it.
I get that you would want to authn the hardware itself. If that is your point, sure, you're right. However, that aims to address a slightly different problem, because then the certificate chain is tied to the hardware only. Note that part of the charm of the _identity_ generated in the program, is that the identity changes if only a single byte of program-binary is different. So it protects from malicious binaries too. (But not bugs in the program itself.)