[Python-Dev] Hash collision security issue (now public) (original) (raw)
Terry Reedy tjreedy at udel.edu
Sat Jan 7 21:53:29 CET 2012
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On 1/7/2012 12:57 PM, Christian Heimes wrote:
Am 07.01.2012 12:02, schrieb Stefan Behnel:
Admittedly, this may require some adaptation for the PEP393 unicode memory layout in order to produce identical hashes for all three representations if they represent the same content. So it's not a drop-in replacement. Is this condition required and implemented at the moment?
If o1 == o2, then hash(o1) == hash(o2) is an unstated requirement implied by "They [hash values] are used to quickly compare dictionary keys during a dictionary lookup." since hash(o1) != hash(o2) is taken to mean o1 != o2 (whereas hash(o1) == hash(o2) is taken to mean o1 == o2 is possible but must be checked). Hashing should be a coarsening of == as an equivalence relationship.
-- Terry Jan Reedy
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