The bitcollider CVS project has new code to calculate the 'kzhash' introduced in Kazaa 2.6 and used in Kazaa magnet links.
It's only been very lightly tested on Windows... an update of the Linux build process, and more testing for its stability and accuracy on multiple platforms is necessary. Adventurous types, please give it a try and let us know any problems you see. (We want to be sure it returns the same values as the "Magnet Builder" app available from Kazaa.)
Server-side support for displaying the new kzhashes will come later.
Thanks go to Phil Morle of Sharman Networks for providing free code which demonstrated the kzhash calculation. It turns out the extra 16 bytes, beyond the original "fthash" (AKA sig2dat) value, are an MD5-based tree hash, combined using a slightly different technique than the THEX/TigerTree approach.