>>>>> "JY" == John Young <j...@pipeline.com> writes:
LJ>> La Jolla Covering Repository LJ>> A (v,k,t)-covering design is a collection of k-element subsets, called LJ>> blocks, of {1,2,...,v}, such that any t-element subset is contained in LJ>> at least one block. JY> What is "covering" and how does it related to cryptology? That quote pretty much answers the question. Perhaps an example would help: Let's choose v=52, like a deck of playing cards (we'll leave the Jokers inside the beltway). Let's use 23-card blocks (k=23) and 5-card hands (t=5). The goal to to find a set of 23-card blocks such that every possible 5-card hand can be found in at least one block. Hense, the set of 23- card blocks covers the set of possible 5-card hands. That can be done trivially by making the blocks be every possible 23-card hand. But ( 52 \choose 23 ) is about 352 trillion. So we want to find a smaller set of blocks which cover every possible 5- card hand. Their site has one covering for (53,23,5) with 243 blocks. It also shows that they started with a 272-block covering and worked their way down to 243 blocks via "dynamic programming". THe application the cryptography is probably something to do with statistical cryptanalysis. Rainbow tables, maybe? -JimC -- James Cloos <cl...@jhcloos.com> OpenPGP: 1024D/ED7DAEA6 _______________________________________________ cryptography mailing list cryptography@randombit.net http://lists.randombit.net/mailman/listinfo/cryptography