# Foundations of Reconfigurable PUFs

## Abstract

A Physically Unclonable Function (PUF) can be seen as a source of randomness that can be challenged with a stimulus and responds in a way that is to some extent unpredictable. PUFs can be used to provide efficient solutions for common cryptographic primitives such as identification/authentication schemes, key storage, and hardware-entangled cryptography. Moreover, Brzuska et al. have recently shown, that PUFs can be used to construct UC secure protocols (CRYPTO 2011). Most PUF instantiations, however, only provide a static challenge/response space which limits their usefulness for practical instantiations. To overcome this limitation, Katzenbeisser et al. (CHES 2011) introduced Logically Reconfigurable PUFs (LR-PUFs), with the idea to introduce an “update” mechanism that changes the challenge/response behaviour without physically replacing or modifying the hardware.

In this work, we revisit LR-PUFs. We propose several new ways to characterize the unpredictability of LR-PUFs covering a broader class of realistic attacks and examine their relationship to each other. In addition, we reconcile existing constructions with these new characterizations and show that they can withstand stronger adversaries than originally shown. Since previous constructions are insecure with respect to our strongest unpredictability notion, we propose a secure construction which relies on the same assumptions and is almost as efficient as previous solutions.

## Keywords

Physically unclonable functions Logically reconfigurable Tamper-resistance## Notes

### Acknowledgements

Dominique Schröder was supported by the German Federal Ministry of Education and Research (BMBF) through funding for the Center for IT-Security, Privacy and Accountability (CISPA www.cispa-security.org) and also by an Intel Early Career Faculty Honor Program Award. Finally, we thank the reviewers for their valuable comments.

## Supplementary material

## References

- 1.Akdemir, K.D., Wang, Z., Karpovsky, M., Sunar, B.: Design of cryptographic devices resilient to fault injection attacks using nonlinear robust codes. In: Joye, M., Tunstall, M. (eds.) Fault Analysis in Cryptography. Information Security and Cryptography, pp. 171–199. Springer, Berlin Heidelberg (2012)CrossRefGoogle Scholar
- 2.Armknecht, F., Maes, R., Sadeghi, A.-R., Standaert, F.-X., Wachsmann, C.: A formalization of the security features of physical functions. In: 2011 IEEE Symposium on Security and Privacy, pp. 397–412, Berkeley, California, USA. IEEE Computer Society Press, 22–25 May 2011Google Scholar
- 3.Armknecht, F., Maes, R., Sadeghi, A.-R., Sunar, B., Tuyls, P.: Memory leakage-resilient encryption based on physically unclonable functions. In: Matsui, M. (ed.) ASIACRYPT 2009. LNCS, vol. 5912, pp. 685–702. Springer, Heidelberg (2009) CrossRefGoogle Scholar
- 4.Brzuska, C., Fischlin, M., Schröder, H., Katzenbeisser, S.: Physically uncloneable functions in the universal composition framework. In: Rogaway, P. (ed.) CRYPTO 2011. LNCS, vol. 6841, pp. 51–70. Springer, Heidelberg (2011) CrossRefGoogle Scholar
- 5.Eichhorn, I., Koeberl, P., van der Leest, V.: Logically reconfigurable pufs: memory-based secure key storage. In: Proceedings of the Sixth ACM Workshop on Scalable Trusted Computing, pp. 59–64. ACM (2011)Google Scholar
- 6.Gassend, B., Clarke, D., van Dijk, M., Devadas, S.: Controlled physical random functions. In: Proceedings of the 18th Annual Computer Security Conference (2002)Google Scholar
- 7.Katz, J., Lindell, Y.: Introduction to Modern Cryptography. CRC Press, Boca Raton (2008) zbMATHGoogle Scholar
- 8.Katzenbeisser, S., Koçabas, Ü., van der Leest, V., Sadeghi, A.-R., Schrijen, G.-J., Schröder, H., Wachsmann, C.: Recyclable PUFs: logically reconfigurable PUFs. In: Preneel, B., Takagi, T. (eds.) CHES 2011. LNCS, vol. 6917, pp. 374–389. Springer, heidelberg (2011) CrossRefGoogle Scholar
- 9.Škorić, B., Tuyls, P., Ophey, W.: Robust key extraction from physical uncloneable functions. In: Ioannidis, J., Keromytis, A.D., Yung, M. (eds.) ACNS 2005. LNCS, vol. 3531, pp. 407–422. Springer, Heidelberg (2005) CrossRefGoogle Scholar
- 10.Kursawe, K., Sadeghi, A., Schellekens, D., Skoric, B., Tuyls, P.: Reconfigurable physical unclonable functions - enabling technology for tamper-resistant storage. In: IEEE International Workshop on Hardware-Oriented Security and Trust, HOST 2009, pp. 22–29 (2009)Google Scholar
- 11.Maes, R., Verbauwhede, I.: Physically unclonable functions: a study on the state of the art and future research directions. In: Sadeghi, A.-R., Naccache, D. (eds.) Towards Hardware-Intrinsic Security. Information Security and Cryptography, pp. 3–37. Springer, Berlin Heidelberg (2010)CrossRefGoogle Scholar
- 12.Ostrovsky, R., Scafuro, A., Visconti, I., Wadia, A.: Universally composable secure computation with (malicious) physically uncloneable functions. In: Johansson, T., Nguyen, P.Q. (eds.) EUROCRYPT 2013. LNCS, vol. 7881, pp. 702–718. Springer, Heidelberg (2013) CrossRefGoogle Scholar
- 13.Pappu, R.S.: Physical one-way functions. PhD thesis (2001)Google Scholar
- 14.Rührmair, U., Sölter, J., Sehnke, F.: On the foundations of physical unclonable functions. Cryptology ePrint Archive, Report 2009/277 (2009). http://eprint.iacr.org/
- 15.Sadeghi, A.-R., Visconti, I., Wachsmann, C.: PUF-enhanced RFID security and privacy. In: Secure Component and System Identification (SECSI), Cologne, Germany, April 2010Google Scholar
- 16.Schulz, S., Sadeghi, A.-R., Wachsmann, C.: Short paper: lightweight remote attestation using physical functions. In: Proceedings of the Fourth ACM Conference on Wireless Network Security, WiSec 2011, pp. 109–114. ACM, New York, NY, USA (2011)Google Scholar
- 17.Suh, G.E., Devadas, S.: Physical unclonable functions for device authentication and secret key generation. In: Proceedings of the 44th Annual Design Automation Conference, DAC 2007, pp. 9–14. ACM, New York, NY, USA (2007)Google Scholar
- 18.Tuyls, P., Batina, L.: RFID-tags for anti-counterfeiting. In: Pointcheval, D. (ed.) CT-RSA 2006. LNCS, vol. 3860, pp. 115–131. Springer, Heidelberg (2006) CrossRefGoogle Scholar