[3] https://github.com/QubesOS/qubes-secpack/blob/master/canar | Qubes OS📢

[3] https://github.com/QubesOS/qubes-secpack/blob/master/canaries/canary-028-2021.txt


Letter from the Qubes security team

The original letter and its detached signature files are available here:


canary-028-2021-letter-qst.txt (https://github.com/QubesOS/qubes-secpack/blob/master/canaries/canary-028-2021-letter-qst.txt)
canary-028-2021-letter-qst.txt.sig.marmarek (https://github.com/QubesOS/qubes-secpack/blob/master/canaries/canary-028-2021-letter-qst.txt.sig.marmarek)
canary-028-2021-letter-qst.txt.sig.simon (https://github.com/QubesOS/qubes-secpack/blob/master/canaries/canary-028-2021-letter-qst.txt.sig.simon)


2021-08-31

Dear Qubes community,

As you can see in Qubes Canary 028 [1], Joanna has requested that she be
removed from the list of canary signers [2], and we have agreed to this
request. A careful reader might recall that, when Joanna left the Qubes
security team in 2018, we wrote [3]:

| However, due to the nature of PGP keys, there is no way to
| guarantee that Joanna will not retain a copy of the QMSK after
| transferring ownership to Marek. Since anyone in possession of the
| QMSK is a potential attack vector against the project, Joanna will
| continue to sign Qubes Canaries in perpetuity.

So, why this change now? It's still true that we (except Joanna herself,
of course) can't guarantee that Joanna did not really retain any copies
of the private portion of the Qubes Master Signing Key. Continuing to
have her sign the canaries on time every few months seemed like a
harmless commitment back then but turned out to require quite a lot of
effort now that Joanna is no longer involved in the project's day-to-day
business. Therefore, we reevaluated whether this is worth the effort
and decided against it. If Joanna were lying about deleting all her
copies of the private portion of the Qubes Master Signing Key, it is
equally possible that she could lie when signing a canary. Therefore,
we do not believe that her ceasing to sign canaries constitutes a
security problem.

This is a good reminder that canaries help only in a very specific
scenario, namely if someone (1) wants to act honestly, (2) is prevented
from stating that a compromise has occurred, and (3) is not forced to
state that no compromise has occurred. For example, this canary scheme
is designed to help if we were ever served with a government warrant
with an attached gag order that prohibited us from discussing the
warrant (the second condition) but that did not compel us to continue
signing and publishing canaries against our will (the third condition).
However, this will not work if the adversary is willing to coerce us
into signing and publishing statements or if signers are willing to lie
by signing statements they know to be false. Hence, this canary scheme
is limited and fallible, which is why we have always included a
statement to this effect in every canary.

Regards,
The Qubes security team
https://www.qubes-os.org/security/

[1] https://github.com/QubesOS/qubes-secpack/blob/master/canaries/canary-028-2021.txt
[2] https://github.com/QubesOS/qubes-secpack/blob/master/canaries/canary-028-2021-letter-joanna.txt
[3] https://www.qubes-os.org/news/2018/11/05/qubes-security-team-update/