[RC5] After RC5-64?

David McNett nugget at slacker.com
Fri Sep 10 09:55:40 EDT 1999

On 08-Sep-1999, Sven wrote:
> I actually would like to know if we are testing keyspace front to back
> ie, started at 1 and going on and on and on, untill the last key is
> tested. Statistically we would probably find the solution quicker if
> we'd test the keyspace in a random order.

This is a pretty frequent subject, it might be wise to consult the
archives for the debate on this issue.  The bottom line is, no,
statistically there is no benefit to any ordering method, so sequential
is used to reduce complexity.  In rc5-56 we did randomly distributed
blocks, but this was done so that our competition (cyberian and infinite
monkeys) would not be able to benefit from our completed keys.  With no
competition in rc5-64 such a motivation does not exist.

Since no one key is any more likely than any other key, it doesn't matter
which one we test next.

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