[patrakov]

It is not because of an unencrypted swap partition. It is because, even if it is encrypted, you know the key and can thus replace the image with an arbitrary modified one, or, in theory, with a hacked version of a Windows boot loader, which would break DRM.

There were some movements to remove this restriction, on the condition that the encryption key is properly sealed in the TPM and is not extractable.

[Operative0198]

Except you'd have to know the encryption passphrase to unlock the swap partition. Only after this step can you use the stolen key to manipulate the state of trusted images.

TPM has never been a pre-requisite for secureboot nor kernel_lockdown. Infact the proposal you are speaking of sounds very exclusionary since TPM hardware is still relatively new and not ubiqitous.

[patrakov]

Correct. But you do know the passphrase, and, from the viewpoint of Secure Boot and the locked-down kernel, you (the legitimate owner) are also the attacker who tries to run some unapproved kernel-mode code and will stop at nothing in order to do that.