[boost] [bigint] Integer data type larger than 64 bits?

I have encountered the need for an integer data type larger than 64 bits to prevent overflow when doing algebra on 32 bit integer data. I notice that there is mention of a couple proposed boost big int libraries in the archive. Is there a boost library that provides this currently, or is there a library nearing acceptance level quality that I should use? I am not eager to take on a non-boost/non-stl dependency because I intend to submit the geometry library I need this for to boost. Thanks, Luke