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Old 18th March 2007, 15:47   #224  |  Link
arnezami
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Join Date: Sep 2006
Posts: 390
Ok. I did some simulations. It appears my estimates are somewhat off. But still practical.

For finding 58 of the 64 keys (per cluster) we need approx 146 volunteers.

For finding 60 of the 64 keys (per cluster) we need approx 169 volunteers.

For finding 63 of the 64 keys (per cluster) we need approx 239 volunteers.

For finding 64 of the 64 keys (per cluster) we need approx 308 volunteers.

(this is based on random distribution of the keys)

Thats quite a bit more than I guessed earlier but still very doable.

The question is: do we even need so many of the keys per cluster to be safe? In other words: assume they revoke all released keys (say 60 of all 64 keys for each column). How big a chance is there that some/many innocent devices get revoked in the process? My bet is (although we could do the math on this properly) that there will be quite a lot of innocents revoked if they would do that. Especially since different movies would require keys from different columns. And there are bound to be innocents that do not have the keys in those columns (for at least some movies) if they revoke all these keys.

Personally I think its better to be safe than sorry: 64 out of 64 will always be safe (with maybe a few columns with 63 or 62)

There is also the possibility they aren't even using all 64 keys (within clusters) but are only using a subset of those (maybe some sequential non-random distribution). This could have both advantages (less keys per cluster is easier) aswell as disadvantages (how do you know you have all keys that are in use?) But when you have enough voluntiers there won't be any risk of missing keys.

arnezami

PS. For 256 keys per cluster (16K rows) it would take around 1000-1500 voluntiers to get around 250-256 keys for each column. Thats starting to get somewhat impractical. But maybe not. Since we can take all the time in the world for more people to join the effort.

Last edited by arnezami; 18th March 2007 at 16:52.
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