Re: Hmm... (discoveries about BIGNUM code)

[Richard Levitte - VMS Whacker]

From: Richard Levitte - VMS Whacker <[EMAIL PROTECTED]>

levitte> >                      if (al == j)
levitte> >                              {
levitte> >                              if (bn_wexpand(a,k*2) == NULL) goto err;
levitte> >                              if (bn_wexpand(tmp,k*2) == NULL) goto err;
levitte> >                              bn_sqr_recursive(rr->d,tmp_bn->d,al,tmp->d);
levitte> 
levitte> 
levitte> The conclusion is that it should be possible to remove the expansion
levitte> of a completely in the code above.

It was sane thinking, although I believe the above code to be overly
careful.  Unless I still misunderstand something about bn_sqr_recursive(),
The only thing it requires from the length of a->d is that it's even.
The code above and the log for revision 1.7 indicates that
bn_sqr_recursive() requires a length that is a power of two.  Now,
inte teh above code, j is a power of two, unconditionally (because
the value was calculated from '1<<(j-1)', that's why), so it's already
checked that a->d has the correct length to be useful according to the
criteria.  Expanding it to twice that size is still, as far as I can
see, completely needless since bn_sqr_recursive() won't look further
than the end of the input data.

I'd still like someone to review my thoughts as a sanity check.

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