# Re: A basic question about hashing

**From:** Mok-Kong Shen (*mok-kong.shen_at_t-online.de*)

**Date:** 09/15/04

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Date: Wed, 15 Sep 2004 11:27:39 +0200

Mok-Kong Shen wrote:

.... I have actually also a second and simpler scheme

that employs similar methodology, which I like to mention

here: One employs a bijective polynomial to do the same

as a block cipher does in CBC. The process, if desired,

could be repeated, i.e. with the last value used as IV

for the next round, preferrably with a different polynomial.

(The final value could also be polynomial transformed a

last time.)

It may be mentioned that the motivation is that (1) While

a block cipher has a key and is invertible, a bijective

polynomial has no key and is (assumed to be) hard to invert,

which is what hashing would need, (2) The analogous CBC-MAC

has been shown to be of value in practice and (3) Other

appropriate block chaning modes could be employed in place

of CBC, if desired, e.g. using the sum of all previous

output-blocks (corresponding to ciphertext blocks) to chain

instead of using simply the previous output block from the

polynomial.

M. K. Shen

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