# Re: Nonlinear combination of streams

*From*: Maaartin <grajcar1@xxxxxxxxx>*Date*: Sat, 13 Mar 2010 12:56:43 -0800 (PST)

On Mar 13, 9:16 pm, Maaartin <grajc...@xxxxxxxxx> wrote:

You could do something multiplication in

a field with a prime of the form 2^k + 1 [e.g. p=257] then just

promote all values into 1..256, then multiplication is a BBM,

How? The multiplication returns one result, but you need two, don'tyou? Ritter writes:

"Balanced Block Mixing: An orthogonal pair of Latin squares which

reversibly mix two input blocks or values of some power-of-2 size into

two output blocks of the original size.".

Or do you mean computing

(X, Y) -> (a*X+b*Y, c*X+d*Y)

in a GF where a, b, c, d, and a*d-b*c are all co-prime to the

characteristic of the field? In the latter case, it's clear.

No, it's not. In GF(256) or GF(257) it would work, but with your

"values promotion" you have only the multiplicative group of GF(257)

and no field. So I'm confused in both cases.

.

**References**:**Nonlinear combination of streams***From:*Mok-Kong Shen

**Re: Nonlinear combination of streams***From:*Tom St Denis

**Re: Nonlinear combination of streams***From:*Maaartin

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