On Tuesday, August 29, 2017 at 11:38:59 AM UTC-4, Patrik Hagara wrote:
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> On 08/29/2017 04:50 PM, [email protected] wrote:
> > Leo Gaspard,
> > 
> > I have read about AEM but have never used it, it seems like it is
> > geared towards protecting from USB's with malicious firmware on
> > them.
> > 
> > Does AEM actually verify the integrity of /boot before using?  This
> > is what I am looking for, either a method of encrypting /boot or
> > even better, a secure method to verify its integrity during boot
> > 
> 
> AEM does verify the integrity of /boot using the TPM seal/unseal
> operation. If any of the boot components change, AEM falls back to
> regular, unmeasured boot -- the user is expected to notice this and
> cease using the potentially-compromised system (the lack of explicit
> indication of failed AEM boot is deliberate, see the last FAQ item at
> [1]).
> 
> The security provided by AEM is much more stronger than encrypted
> /boot could ever offer, because as already pointed out, there is
> always a little first-stage bootloader stub on the disk unencrypted
> and it would be easy to overwrite it with a malicious version that
> would intercept the encryption passphrase and exfiltrate it using eg.
> unused disk sectors.
> 
> If someone did the above with AEM, the TPM would refuse to useal the
> AEM secret as the platform state would be different.
> 
> The feature protecting dom0 from malicious USB devices [2] serves a
> different purpose and is not related to AEM. Plus, you always need to
> disconnect all untrusted USB devices while rebooting Qubes, regardless
> of whether you have USB qube set up or not.
> 
> 
> Cheers,
> Patrik
> 
> 
> [1] https://blog.invisiblethings.org/2011/09/07/anti-evil-maid.html
> [2] https://www.qubes-os.org/doc/usb/
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my problem is unfortunately i can't keep buying new pc's. SO maybe its all for 
naught for me.. Also AEM does not seem as reliable as secureboot. Alot of 
issues on threads with some people. It seems complicated. even false alarms. 
But I really do think they are supposed to compliment each other.  trusted boot 
and measured boot yes? AEM definitely comes in handy for people who would find 
it nescessary to buy new equipment.  

But I would still want an encrypted boot, if I was going to use aem,  and key 
on a external usb disk,  which unfortunately means I could not use a sys-usb.  
Am I wrong about this?  Does this change in 4.0?

So this is where the what fits into you "security model"   What are you more 
concered about. I assumed we had to choose between aem  vs sys-usb?  For people 
travelling with laptops in strange places where physical compromise is more 
likely aem is a good option.  Some people would prolly not just buy a new 
laptop but know when to destroy theirs too lol.

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