Of course you haven't seen such a thing. If factoring RSA keys requires exponential time, such an algorithm is obviously not possible. Were it possible, you could factor in time proportional to the the number of bits in the key. Anyone who had such a function would either be famous or wouldn't be talking.
Perry
How about some evidence on it? I see no reason to compare taking a key and determining if it is too large or too small as being necessarily equivalent to factoring a large number. I do not need to know the number exactly to determine its relative magnitude. NSA doesn't say much... I have found no evidence so far in my search for such a methodoligy, as a matter of fact I have found no evidence that anyone has ever even looked at such a scheme. If you know something I haven't been able to find then pleas enlighten me so I can move on to other more worthy things to play with... Thanks for the feedback...