#26846: prop289: Leave unused random bytes in relay cell payload
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Reporter: dgoulet | Owner: dgoulet
Type: enhancement | Status: assigned
Priority: Medium | Milestone: Tor:
| 0.3.5.x-final
Component: Core Tor/Tor | Version:
Severity: Normal | Resolution:
Keywords: prop289, 035-roadmap-subtask | Actual Points:
Parent ID: #26288 | Points:
Reviewer: | Sponsor: SponsorV
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Comment (by arma):
My {{{task26846-demo}}} branch has two commits that are an example of what
we could do here.
If we like this direction, they'll still need unit tests and a changes
file (at least).
We might also want to make a consensus parameter for the "how often to
leave a byte empty" choice, but also maybe that's just overengineering
things.
And maybe flipping coins every time we consider packaging is expensive --
we could probably get away with some cheaper randomness if we wanted. But
I think we should only do that if we are pushed into it, since cheaper
randomness is so easy to regret.
I also thought about keeping a "how many cells have we packaged on this
circuit" counter and then just doing some sort of mod operation to decide
which ones to decrement. But I decided that doing it probabilistically is
better, because right now we pad short payloads with 0 bytes (#26228), and
somebody should check my logic but I think a rare but unpredictably short
payload with a zero is enough to accomplish our goal here -- that is, we
don't actually need a random byte, we just need to have it be
unpredictable when the 0 will appear.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26846#comment:3>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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