I hate to rain on your parade, but...

**the RC5-72 contest is pointless, unwinnable and wasteful.**

### Pointless

The contest is

scientifically pointless. Cracking a single

key
by

brute force is not

rocket science, it's been done before.
Successfully cracking that one particular

key will not
weaken RC5-72 as a cryptographic

algorithm one bit, brute force is
the lowest common denominator attack against all algorithms.
And unlike the previous

DES and

RC5-56 challenges, this contest
cannot even serve to point out how insecure RC5-72 is, because nobody
uses RC5-72 and because...

### Unwinnable

The contest is not

winnable in a reasonable amount of time.
As of

today, distributed.net expects that

keyspace
exhaustion will take place in 788,747 days. For the mathematically
impaired, that's 2161

years. During the RC5-64 contest, it took on
average 261 days for processing speed to double; if this doubling keeps
up for 5 years (that's 7 doublings), you're only looking at another 17 years
of number crunching

*after* those 5 years. Do you seriously expect to keep going until 2025?

Another way to look at the situation:
buying a lottery coupon for $1, with a possible yield of $1,000,000 if
you get 7 right, has an expectation of $1 * 6.5e-8 * 1e6 = $0.01.
However, the odds of the key being found today are 0.000127%, and of the
1392922 blocks completed 8744 (0.63%) were done by the E2 team.
The odds of E2 receiving the price money tomorrow are thus
1.01e-12, or 0.000000001%. That's a lotta zeros.

But hey, you never know. With a prize money of $10000 in the offering,
we need to have a 'bet' of less than $0.000000001 ($1e-10) per day to
beat the odds of the lottery. But processor power is free, right?

### Wasteful

Wrong. Back in the

halcyon days of RC5-56 and the

DES Challenges,
computers didn't make a distinction between

idling and

crunching,
so it was a great idea to use those spare cycles for something (remotely)

productive. But this is no longer true: modern-day power-sucking CPUs

*do* have
circuitry that lets them idle and cool off when the processor is just
running

NOPs. Thus, keeping a number cruncher running 24 hours a day will
stress your processor, requiring full ventilation and running up your
power bill.

To illustrate, a standard Pentium III, without the requisite array of
cooling fans, sucks down around 30W when running at full speed. Run that
sucker for 24 hours, and you've run up a bill of 0.72 kilowatt-hours, or
about 3.6¢ assuming 5¢/kW/H.

### Conclusions

If you want to earn money for E2...

...it would be 36,000,000,000 times more efficient to buy a lottery ticket
each day. Then again, 3.6¢ a day adds up to $13.14 a year, so why
not donate the sum directly?

If you want to advance

science through

distributed computing...

...you might want to try folding proteins (**folding.stanford.edu**), finding a cure for cancer
(**www.ud.com**),
looking for Sierpinski numbers (**www.seventeenorbust.com**), or even
optimal Golomb rulers (**www.distributed.net/ogr/**).

### References

My elementary statistics course.
Calculations done on the back of a virtual napkin, so corrections welcome.
Lottery probability based on the Finnish model, ie. 39 balls with
7 picked and 7 needed for the grand prize.