[rc5] Checking for 64 bit RC5 on the fly?

Fedor Kouranov ted99 at ibm.net
Wed Jun 25 20:24:33 EDT 1997

On 06/25/97 Marc Briceno <marc at c2.net> said:

>I strongly support getting a start on the 64 key ASAP. [Frankly, I believe
>the 56 bit RC5 crack to be a waste of time. But it seems that this one has
>to be cleared before the next interesting target will be addressed: a 64
>bit key.]

To those who didn't get it: there is NO need to start a separate search on
64-bit keyspace. To use 56-bit result on the 64-bit search we only need to
1) completely exhaust 56-bit keyspace (we'll call it 'switching to 64-bits
on-the-fly'), 2) check 'false alarms' from the 56-bit search on the 64-bit
search (done by servers) and 3) modify the 64-bit clients to avoid keys
that end in null byte.

No modifications needed.

OTOH, if we get real, 64 bits are still infeasible to exhaust.

BTW, could the results from 48-bit search be used in our effort
(practically, not technically)?

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