[rc5] keyspace flaw

Benedikt Eric Heinen beh at icemark.ch
Thu May 29 10:09:38 EDT 1997


> > it stands to reason that RSA selected keys that will fall at
> > or beyond the 50% threshold of the keyspace.  has any thought
> > been given to modify the servers to randomly select key ranges
> > throughout the entire keyspace?
> Actually it would stand to reason that any key would be just as unlikely
> as any other key.  This is supposed to be a real test of rc5, and RSA
> selecting one key over another can only reduce the security of
> the algorithm (assuming no weak keys).

Still, I think that this random blocks idea isn't bad. I mean, we're
probably not the only effort to try and break the key, so as long as all
the efforts plough through all possible combinations starting with key 0x0
up to the maximum, that means, that only the fastest group has a chance of
winning, since all the other efforts are checking keys that have been
dealt with already.

Now, can anybody round here prove, that we're the fastest of the
competing groups? I mean, is there even a way to know which groups are
competing (I do not refer to the email groups within our effort, but
groups independent of bovine)?

Selecting key blocks at random does seem somewhat reasonable, I think...

  Benedikt

signoff

          Hiroshima '45           Chernobyl '86           Windows '95

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