I see your point, but let's put it into perspective. distributed.net, one of the more popular distributed client sites, participates in RSA's RC5 cracking challenges. In July 2002, they cracked RC5-64, which uses a 64-bit key. It took 331,252 people, five years, and tests of 15,769,938,165,961,326,592 keys to get the job done.
Now, certainly, it wouldn't take them that long now, because computers are faster. So that's fine, let's say it would have taken them 1 year instead of 5 years. Indeed, this is how they characterized their cracking speed at their fastest clip:
|at our peak rate we could expect to exhaust the keyspace in 790 days. Our peak rate of 270,147,024 kkeys/sec is equivalent to 32,504 800MHz Apple PowerBook G4 laptops or 45,998 2GHz AMD Athlon XP machines or (to use some rc5-56 numbers) nearly a half million Pentium Pro 200s.
The next challenge, RC5-72, will require 256 times more work
to perform. So even if they could have cracked RC-64 in 1 year, that would require 256 years on the same computer hardware. Factoring in hardware improvements over time, maybe it would take only 50 years. Getting 10 times as many people to participate---3 millon
people---it would take only, say, 10 years. (It's not a strict factor of 10 reduction, because over the shorter time span you get less of a benefit from the faster computers.)
OK, so now we're down to my 10 year prediction. Only why should the DVD Forum take chances? Suppose they use an encryption system with the strength of, say, RC5-128, a 128-bit key. Then it will take 20 billion billion
times the effort to crack it as it took to crack 64-bit RC5. Even if everyone on the planet participated, it would never happen in our lifetimes, short of a major breakthrough in quantum computation. Heck, even RC5-96 would take almost 5 billion
times the effort that RC5-64 did. Again, not in our lifetimes.
Again, I can't say that HD-DVD will use such strong encryption. But I think it's really a bit deceiving to claim that we're getting better at cracking codes. All we're doing is forcing people to use longer
codes. By choosing key lengths liberally, you really can protect against even the best efforts of the Slashdot crowd.