[tor-bugs] #23416 [Core Tor/Tor]: Document the precision and limits of sample_laplace_distribution()

[Tor Bug Tracker & Wiki]

#23416: Document the precision and limits of sample_laplace_distribution()
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     Reporter:  teor          |      Owner:  (none)
         Type:  enhancement   |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.3.2.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  tor-relay, privcount
Actual Points:                |  Parent ID:  #23061
       Points:  1             |   Reviewer:
      Sponsor:                |
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 The function documentation of sample_laplace_distribution() should answer
 the following questions:
 * what is the range of outputs?
 * what is the precision of the outputs?

 add_laplace_noise() should document, and possible enforce:
 * what is the maximum `delta_f / epsilon` value that can be used within
 the limits of double precision arithmetic?
   * to preserve differential privacy, the low bits have to be obscured by
 the noise. So this can be at most 2^53^.
 * what is the minimum `delta_f / epsilon` value that can be used within
 the limits of double precision arithmetic?
   * (zero provides no differential privacy)

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23416>
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