[RC5] Time out and DES-II-2 challenge

Jason Untulis untulis at netgate.net
Wed Jul 1 18:35:16 EDT 1998


gindrup at okway.okstate.edu wrote:

[...]

:      For a while, some of the clients would lose a block if they were 
:      shut down in the middle of one.  This may or may not still be the 
:      case.  (I haven't checked.)  Thus, if you were using smaller blocks, 
:      you lost less work.  Similar comments hold if your machine regularly 
:      crashes or you have highly irregular power.

One other blocksize-related note to add to Eric's fine summary. Early in
RC5-64, when the new blocksizes were added (original RC5-56 blocks were
only 2^28 AFAIR), there were bugs in handling the 2^31 block size,
presumably related to the fact that 2^31 is the maximum size of a 32 bit
signed integer. (Not a difficult mistake for the coders to make...) Many, if
not most people, who wanted bigger blocks chose the 2^30 size and probably
left it there.

The assertion made in Adam's 2.7100 announcement is that this 2^31 block
handling has been fixed. Looking at the Readme I've seen no indication in
the version history of this. You may want to test this out before DES-II-2
starts...
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Jason Untulis, Ravenous Media Consumer    /\    /        untulis at netgate.net
<http://www.netgate.net/~untulis/>    \  /==\  /          untulis at netcom.com
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