Meh, it's an interesting exploit for sure (the USB key simulating Enter key being pressed every 15ms is cute). But IMO unless you run a very hardened setup, protecting against evil maid attacks (wherein the attacker has physical access to your machine in its entirety) is really hard, and possibly always will be. In a hardened setup you lock down the emergency initrd shell - either it's not allowed at all, or it uses…
You raise a valid point, but this attack is particularly alarming because it circumvents a TPM, which is a hardware module that was specifically designed to protect against evil-maid class of attacks, e.g. every iPhone after the 5S uses its Secure Enclave (a TPM) to enforce time delays between passcode attempts [0], so that a physical attacker can't brute force the passcode. (Incidentally, the attack described in the…
I'd trust this setup to prevent drives that were removed from servers from being decrypted (like for recycling), but it's basically useless against any other class of attack.
It's good to see publicized exploits of it though; that way people can link to this blog post if a pointy-haired-boss tries to misapply this class of disk encryption.