[GHC] #7634: MD5 collision could lead to SafeHaskell violation

[GHC]

#7634: MD5 collision could lead to SafeHaskell violation
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        Reporter:  shachaf           |                   Owner:  ekmett
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  ⊥
       Component:  Core Libraries    |                 Version:  7.6.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Other             |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Changes (by ekmett):

 * cc: core-libraries-committee@… (added)
 * milestone:  7.12.1 => ⊥


Comment:

 Acknowledging that this probably won't get addressed in the foreseeable
 future by pushing it out to _|_.

 Given that the two strings would have to be legal UTF-32 encodings of text
 that can actually be entered you wind up with a '''huge''' number of fixed
 bits in the strings on either side, which very quickly raises the cost of
 an attempted birthday attack and also forbids a number of birthday attack
 generation techniques.

 That said, saying a cryptographic attack isn't possible for hand-wavy
 reasons doesn't have a great track record for success. :)

 Techniques for finding small single block collisions via random walks,
 like https://eprint.iacr.org/2014/871.pdf are probably the most likely
 source of such a vulnerability. Notice how similar the colliding document
 pair are. In theory you could prune the walk to keep the paths always
 within the space of valid inputs. I lack a few weeks (months?) of HPC
 cluster time to test this hypothesis, however.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7634#comment:5>
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