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Physically Unclonable Functions(PUFs) for IP protection on FPGA
Sandeep S. Kumar, Philips Research Europe
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| Reusable IP is a major source of revenue for many FPGA IP vendors and their protection
is of high importance. The main issues that are involved are: (a) the IP being leaked
to parties other than those originally intended to obtain it and (b) the over building
of the IP than the licensed amount. IP to be used on SRAM FPGAs are more vulnerable to
these types of misuse as their programming bitstream has to be stored on external
non-volatile memory. Hence the bitstream can be easily copied by an attacker and used
on a similar off-the-shelf FPGA. FPGA manufacturers have tried to solve the problem
using various ways to encrypt the bitstream stored in the external non-volatile memory.
However, these methods rely on battery backed or flash based key storage on the FPGA
which themselves introduced other problems for a field deployment and hence were not
very widespread. Simpson and Schaumont proposed a new approach based on Physically
Unclonable Functions(PUFs) for IP protection on FPGAs. Their work only assumed the
existence of a PUF without a real construction. This presentation shows two practical
intrinsic PUFs on the FPGA which require no hardware modification and can be used for
IP protection. The first PUF is based on uninitialized SRAM start-up values in the
embedded SRAM memories which are intrinsic in current FPGAs. The second is the Butterfly
PUF which is built using cross-coupled circuits on the FPGA matrix. We also present the
experimental results on various tests done under different environmental conditions to
prove their stability for commercial applications. |
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