designer + developer | résumé

arbiter puf

embedded cybersecurity


a puf, or physically unclonable function, is a hardware based cryptographic encryption scheme that gets it security from process differences in manufacturing identical chips. in particular, an arbiter puf applies a race signal across "identical" transistors and outputs a one or zero depending on which one reaches an arbiter gate first. what is unique about a hardware based encryption scheme is that any form of a side channel attack would alter the environment the chip operates in, thereby altering the scheme itself. this means that such a device would be secure against any sort of physical hardware attack.

while my mentor focused on breaking this particular encryption scheme using an evolutionary algorithm, i dedicated my summer research to implementing a client that could, given a set of parameters, successfully emulate a hardware arbiter puf. this was an interesting project because of the hardware and software limitations. i was limited to programming an 8-bit atmega smart card and could only work in low level c. as a result, much of my code had to be extremely efficient and at times hacky. for example, when implementing an lfsr, i had to make use of optimizations such as loop unrolling and function inlining. nevertheless, i was able to successfully emulate a hardware arbiter puf by the end of my summer. this means that it is possible for any malicious attacker to spoof a puf given that they recover enough data from the original hardware version.

this research project was done during the summer of 2014 under the direction of georg becker, phd at ruhr universität bochum, germany in their embedded securities group.


copyright eric li.