B Discussion Two straightforward but biased interpretations of our results

B discussion two straightforward but biased

This preview shows page 14 - 16 out of 16 pages.

B. Discussion Two straightforward, but biased interpretations of our results would be the following: (i) All Strong PUFs are insecure. (ii) The long-term security of electrical Strong PUFs can be restored trivially, for example by increasing the PUF’s size. Both views are simplistic, and the truth is more involved.
Image of page 14
1890 IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, VOL. 8, NO. 11, NOVEMBER 2013 Starting with (i), our current attacks are indeed suf fi cient to break several delay-based PUF implementations. But there are a number of ways how PUF designers can fi ght back in future de- signs. First, increasing the bitlength in an XOR Arbiter PUF or Lightweight Secure PUF with XORs increases the effort of the presented attacks methods as a polynomial function of with exponent (in approximation for large and small or medium ). At the same time, it does not worsen the PUF’s sta- bility [9]. For now, one could therefore disable attacks through choosing a strongly increased value of and a value of that corresponds to the stability limit of such a construction. For ex- ample, an XOR Arbiter PUF with 8 XORs and bitlength of 512 is implementable by standard fabrication processes [9], but is currently beyond the reach of our attacks. Similar considera- tions hold for Lightweight PUFs of these sizes. Secondly, new design elements may raise the attacker’s complexity further, for example adding nonlinearity (such as AND and OR gates that correspond to MAX and MIN operators [24]). Combinations of Feed-Forward and XOR architectures could be hard to machine learn too, partly because they seem susceptible only to different and mutually-exclusive ML techniques. Moving away from delay-based PUFs, the exploitation of the dynamic characteristics of current and voltage seems promising, for example in analog circuits [7]. Also special PUFs with a very high information content (so-called SHIC PUFs [39], [40], [21]) could be an option, but only in such applications where their slow read-out speed and their comparatively large area consumption are no too strong drawbacks. Their promise is that they are naturally immune against modeling attacks, since all of their CRPs are information-theoretically independent. Finally, optical Strong PUFs, for example systems based on light scat- tering and interference phenomena [34], show strong potential in creating high input-output complexity. Regarding view (ii), PUFs are different from classical cryp- toschemes like RSA in the sense that increasing their size often likewise decreases their input-output stability. For example, raising the number of XORs in an XOR Arbiter PUF and Lightweight PUF has an exponentially strong effect both on the attacker’s complexity and on the instability of the PUF. We are yet unable to fi nd parameters that increase the attacker’s effort exponentially while affecting the PUF’s stability merely polynomially . Nevertheless, one practically viable possibility is to increase the bitlength of XOR Arbiter PUFs and Lightweight PUFs, as discussed above. Future work will have to show whether the described large polynomial growth of the latter method can persist in the long term, or whether its high degree can be diminished by further analysis.
Image of page 15
Image of page 16

You've reached the end of your free preview.

Want to read all 16 pages?

  • Summer '15

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask ( soon) You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors