&gt; I also wonder what other things they may have locked down on the laptop itself to try to stymie key exfiltration?<p>The private keys are in the HSM, a separate device (according to the article, connected by an Ethernet cable). The laptop doesn&#x27;t have access to them.<p>The main risk I can imagine would be a compromised laptop signing a different KSR which has extra keys, and saving it in a hidden area of the USB key, while pretending to sign the original KSR (and presenting the hashes of the original KSR to the operators).