On the vulnerability of FPGA bitstream encryption against power analysis attacks: extracting keys from Xilinx Virtex-II FPGAs

Over the last two decades FPGAs have become central com-ponents for many advanced digital systems, e.g., video signal processing, network routers, data acquisition and military systems. In order to protect the intellectual property and to prevent fraud, e.g., by cloning an FPGA or manipulat-ing its content, many current FPGAs employ a bitstream encryption feature. We develop a successful attack on the bitstream encryption engine integrated in the widespread Virtex-II Pro FPGAs from Xilinx, using side-channel anal-ysis. After measuring the power consumption of a single power-up of the device and a modest amount of off-line com-putation, we are able to recover all three different keys used by its triple DES module. Our method allows extracting secret keys from any real-world device where the bitstream encryption feature of Virtex-II Pro is enabled. As a conse-quence, the target product can be cloned and manipulated at will of the attacker. Also, more advanced attacks such as reverse engineering or the introduction of hardware Trojans become potential threats. As part of the side-channel attack, we were able to deduce certain internals of the hardware en-cryption engine. To our knowledge, this is the first attack against the bitstream encryption of a commercial FPGA re-ported in the open literature. 1