Dynamic Intellectual Property Protection for Reconfigurable Devices

The distinct advantage of SRAM-based field programmable gate arrays (FPGA) is their flexibility for configuration changes. However, this opens up the threat of theft of Intellectual Property (IP) since the system configuration is stored in easy-to-access Flash memory. To prevent this, high-end FPGAs have already been extended with symmetric-key decryption engines used to load an encrypted version of the configuration that cannot simply be copied and used without knowledge of the secret key. However, such protection systems based on straightforward use of symmetric cryptography are not well-suited with respect to business and licensing processes, since they are lacking a convenient scheme for key transport and installation. We propose a new protection scheme for the IP of circuits in configuration bit files that provides a significant improvement to the current unsatisfying situation. It uses both public-key and symmetric cryptography, but does not burden FPGAs with the usual overhead of public-key cryptography: While it needs hard-wired symmetric cryptography, the public-key functionality is moved into a temporary configuration bit stream for a one-time setup procedure. This approach requires only very few modifications to current FPGA technology. Using five basic stages, the new protection scheme allows new accounting models for volume licensing of IP, with automated key installation on FPGAs taking place at the customer´s site.