[tor-bugs] #23061 [Core Tor/Tor]: crypto_rand_double() should produce all possible outputs on platforms with 32-bit int

[Tor Bug Tracker & Wiki]

#23061: crypto_rand_double() should produce all possible outputs on platforms with
32-bit int
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  nickm
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.2.x-final
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.2.2.14-alpha
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-relay, security-low, privcount,  |  Actual Points:  0.5
  031-backport, 030-backport, 029-backport, 028  |
  -backport-maybe, 027-backport-maybe, 026       |
  -backport-maybe, review-group-22               |
Parent ID:                                       |         Points:  0.1
 Reviewer:                                       |        Sponsor:
                                                 |  SponsorQ
-------------------------------------------------+-------------------------

Comment (by catalyst):

 The potential problem is less about omitting rare small values and more
 about missing lots of representable intermediate values.  I think with
 this kind of approach we're losing half of the representable values
 between 0.25 and 0.5-2^-52^; 3/4 of the possible values between 0.125 and
 0.25-2^-51^, etc., which was kind of the motivation for the Downey paper.
 We might decide we don't care, but I think that's highly dependent on what
 the caller ends up doing with the results.  (We should also document this
 choice; the comment currently focuses on small rare values instead of
 "holes" in the range.)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23061#comment:26>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online