Researchers in Germany have released two papers detailing how security of the bitstream on Xilinx FPGAs can be compromised.
The first paper (11 pages) discusses power analysis attacks and extracting keys from Virtex-II devices.
The second (3 pages) describes an analysis of the Virtex 4 and 5 bitstream encryption mechanism.
Via Slashdot.
I think you may have swapped the order of the papers. I believe the Virtex-II Pro breakage was first, and the second paper analyzes portability of that sidechannel attack to the V4/V5.
Thanks. Switched them back now.