[tor-bugs] #22006 [Core Tor/Tor]: prop224: Validate ed25519 pubkeys to remove torsion component

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#22006: prop224: Validate ed25519 pubkeys to remove torsion component
------------------------------+------------------------------------
     Reporter:  asn           |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.3.1.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  tor-hs prop224 ed25519
Actual Points:                |  Parent ID:  #21888
       Points:                |   Reviewer:
      Sponsor:  SponsorR-can  |
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 We should validate ed25519 pubkeys used in prop224 (like the blinded key)
 to make sure there is no torsion components. In the case of the blinded
 key, this ensures that there are no equivalent keys due to the torsion
 component.

 Please see:
 https://lists.torproject.org/pipermail/tor-dev/2017-April/012164.html
 https://lists.torproject.org/pipermail/tor-dev/2017-April/012213.html

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22006>
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