Tillitis Key – Mullvad spin-off inspired by measured boot and DICE • Hacker News Board

Re: Tillitis Key – Mullvad spin-off inspired by measured boot and DICE

#121

Post by Semaphor » Tue, Sep 20, 2022, 3:48 AM UTC

kfreds wrote: post #108

Semaphor wrote: post #104

Earlier quoted context omitted.

One question, with the two-stage approach, isn’t that a security risk? App 1 gets measured and can’t change, but it needs to identify app 2 in a way that still allows it to be updatable, invalidating the whole security chain. I’m probably not understanding something, so I’d love an explanation (preferably one that non-cryptographers understand)

> One question, with the two-stage approach, isn’t that a security risk? App 1 gets measured and can’t change, but it needs to identify app 2 in a way that still allows it to be updatable, invalidating the whole security chain. It doesn't invalidate it if it works as the application developer intended. The essential idea is that the first mutable boot stage contains a trust policy which somehow verifies the second st…

Ah, so for example challenge-response/public key? The first stage knows the second stage’s public key, and can verify that it knows the private key.

That would make it less secure ("only" as secure as the private key), which is the trade-off the developer made in exchange for an upgradable app, correct?

Re: Tillitis Key – Mullvad spin-off inspired by measured boot and DICE

#122

Post by filleokus » Tue, Sep 20, 2022, 6:27 AM UTC

kfreds wrote: post #110

filleokus wrote: post #72

Cool! Always nice to see extra competition in this space. One thing I've wanted for a while is a way to properly backup a webauthn token. An approach I discussed a couple of weeks ago [1] was: 1: Generate on-hardware webauthn master key on device A. 2: Generate on-hardware key-pair on device B 3: Export B’s public key, import to A 4: On Device A: Encrypt master key with B’s public key 5: Export encrypted master key t…

Hi! Interesting. Which company do you work for? Yes, that'd be possible. I don't know how webauthn works, but if it relies on ECC you could probably do ECDH between all security keys you wanted to carry your master key, and then use the combined ECDH values as the master key.

I work at a consulting firm in Stockholm, my remark about competition was solely from a user/hacker standpoint. My day job is more about security in the higher levels of the stack :-)

Cool! It was a while since I looked in the standards, but I think there definitely is support for using ECC based algorithms.

Looking forward to follow your journey!

Re: Tillitis Key – Mullvad spin-off inspired by measured boot and DICE

#123

Post by kfreds » Tue, Sep 20, 2022, 10:32 AM UTC

filleokus wrote: post #122

kfreds wrote: post #110

Earlier quoted context omitted.

Hi! Interesting. Which company do you work for? Yes, that'd be possible. I don't know how webauthn works, but if it relies on ECC you could probably do ECDH between all security keys you wanted to carry your master key, and then use the combined ECDH values as the master key.

I work at a consulting firm in Stockholm, my remark about competition was solely from a user/hacker standpoint. My day job is more about security in the higher levels of the stack :-) Cool! It was a while since I looked in the standards, but I think there definitely is support for using ECC based algorithms. Looking forward to follow your journey!

Ah, OK! :)