On Sun, May 25, 2008 at 04:10:01PM -0400, Aryeh M. Friedman wrote:

quoted text
> Lets say I have a string of n bits that needs to be filled by repeatedly

> applying some function on k strings of m bits where |m|<|n|.   Assuming

> that m(i) is a random string and n needs to also be random what is the best

> way to do this.  Note it is possible that k*|m|>|n|.   What I have been

> thinking so far is:

>

> ~    Let m' be the average length of m       // this is pre-computable

> ~    Let n be all 0's

>

> ~    for i=0 --> k

> ~       pos=m'*i

>

> ~       xor string k[i] onto n starting at pos   // wrap around if needed

>

> ~    While this is simple I wonder if it can be attacked (determine what

> k[i]) if k*|m|>|n| (it is trivial to attack if k*|m|<=|n|).   Also is there

> some way to make attacking hard if k*|m|<=|n|?

>

> ~    Ideas?

So you want us to do your homework...?
--

Martin Tournoij

carpetsmoker@rwxrwxrwx.net

http://www.daemonforums.org
Information is the inverse of entropy.

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