# Re: Secure permutation of a 1e8 element set

*From*: dwmalone@xxxxxxxxxxxx (David Malone)*Date*: 28 Oct 2008 10:24:26 -0000

"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.

.

**Follow-Ups**:**Re: Secure permutation of a 1e8 element set***From:*Maaartin

**References**:**Secure permutation of a 1e8 element set***From:*Maaartin

**Re: Secure permutation of a 1e8 element set***From:*Joseph Ashwood

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