# Re: A poorman's block encryption algorithm

*From*: Mok-Kong Shen <mok-kong.shen@xxxxxxxxxxx>*Date*: Fri, 12 Mar 2010 18:24:59 +0100

Maaartin wrote:

There's a problem with polynomials you was already told about: They

propagate only towards higher bits (unless you use non-power of two

modulus which is slow). So you can be sure, that a couple of least

significant bits can be found out easily, no matter how many rounds

you do. Starting from them, higher bit can be found, etc. I already

recomennded a remedy, so use it or find another.

Extremely sorry for my poor memory. Could you kindly sketch your remedy

once again or provide a pointer? Concerning predictability of

congruential PRNGs, I previously suggested to use (pseudo-random)

cyclic shift of bits in computer words of the output as a counter-

measure. That could also be done in the present context.

Thanks,

M. K. Shen

.

**Follow-Ups**:**Re: A poorman's block encryption algorithm***From:*Maaartin

**References**:**A poorman's block encryption algorithm***From:*Mok-Kong Shen

**Re: A poorman's block encryption algorithm***From:*Maaartin

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