Generating a random permuttion of the values from 0..N-1 is particularly 
easy.

Assuming that you have a good source of 'random numbers', then you can 
simply:

unsigned char a[N];

for ( i=n-1; i >0; --i )
{
   j = random value in range 0..i
   temp = a[j];
   a[j] = a[i];
   a[i] = temp;
}

And creating the reversed table is also very simple:

unsigned char b[N];

for (i=0; i < N; ++i)
{
    b[ a[i] ] = i;
}

Bob Ammerman
RAm Systems


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