RAW 2014: Random Number Generators on FPGAs

摘要

Random numbers are important ingredients in a number of applications. Especially in a security context, they must be well distributed and unpredictable. We investigate the practical use of random number generators (RNGs) that are built from digital elements found in FPGAs. For this, we implement different types of ring oscillators (ROs) and memory collision-based circuits on FPGAs from major vendors. Implementing RNGs on the same device as the rest of the system benefits an overall reduction of vulnerability to attacks and wire tapping. Nevertheless, we investigate different attacks by tampering with power supply, chip temperature, and by exposition to strong magnetic fields and X-radiation. We also consider their usability as massively deployed components, whose functionality cannot be tested individually anymore, by conducting a technology invariance experiment. Our experiments show that BlockRAM-based RNGs cannot be considered as a suitable entropy source. We further show that RO-based RNGs work reliably under a wide range of operating conditions. While magnetic fields and X-rays did not induce any notable change, voltage and temperature variations caused an increase in propagation delays within the circuits. We show how reliable RNGs can be constructed and deployed on FPGAs.