Re: Secure permutation of a 1e8 element set



"Joseph Ashwood" <ashwood@xxxxxxx> writes:

You simply will not find a secure permutiation, as you noted any permutation
could be simply stored in memory making it inherently weak.

That's probably a little unfair to permutations that one can store.
A arbitary permutation of 1e8 numbers is equivelent to a key size
of about 2513272986 bits, if you count the number of possible
mappings. If I gave you the values of (say) P[0], ... p[999], you
couldn't say much about p[1000], other than it wasn't any of the
previous values I'd given you.

OTOH, if you tried to use it as a more general block cipher, I guess
that might not be a very good idea because the block size would be
a bit small.

David.
.