[tor-bugs] #12999 [Tor Browser]: Use one clock skew per URL bar domain

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#12999: Use one clock skew per URL bar domain
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 Reporter:  arthuredelstein     |          Owner:  tbb-team
     Type:  enhancement         |         Status:  new
 Priority:  normal              |      Milestone:
Component:  Tor Browser         |        Version:
 Keywords:  tbb-fingerprinting  |  Actual Points:
Parent ID:  #3059               |         Points:
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 When #3455 lands, Tor Browser will have a separate Identity (i.e.,
 circuit) for each URL bar domain. JavaScript clock skew fingerprinting is
 one way attackers can try to link Identities. Tor Browser could counter
 this by maintaining a separate clock skew for each URL bar domain.

 When the user browses to a new URL bar domain, Tor Browser would
 1. Create a new circuit
 2. Request clock skew from exit node (already tied to Identity)
 3. Store clock skew in a skew->URL bar domain mapping
 4. Apply clock skew to any JS clock requests under that domain

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12999>
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