Elena Dubrova

Elena Dubrova

Our society becomes increasingly dependent on wireless communications. The tremendous growth in the number and type of wirelessly connected devices in a combination with the dropping cost for performing cyberattacks create new challenges for assuring security of services and applications provided by the next generation of wireless communication networks. The situation is complicated even further by the fact that many end-point Internet of Things (IoT) devices have very limited resources for implementing security functionality. This paper addresses one of the aspects of this important, many-faceted problem - the design of hardware-efficient cryptographic primitives suitable for the protection of resource-constrained IoT devices. We focus on cryptographic primitives based on the invertible mappings of type $\{0,1,\ldots,2^n-1\} \rightarrow \{0,1,\ldots,2^n-1\}$. In order to check if a given mapping is invertible or not, we generally need an exponential in $n$ number of steps. In this paper, we derive a sufficient condition for invertibility which can be checked in $O(n^2 N)$ time, where $N$ is the size of representation of the largest function in the mapping. Our results can be used for constructing cryptographically secure invertible mappings which can be efficiently implemented in hardware.

Elena Dubrova, Mats Näslund, Gunnar Carlsson et al.

The threat of hardware Trojans has been widely recognized by academia, industry, and government agencies. A Trojan can compromise security of a system in spite of cryptographic protection. The damage caused by a Trojan may not be limited to a business or reputation, but could have a severe impact on public safety, national economy, or national security. An extremely stealthy way of implementing hardware Trojans has been presented by Becker et al. at CHES'2012. Their work have shown that it is possible to inject a Trojan in a random number generator compliant with FIPS 140-2 and NIST SP800-90 standards by exploiting non-zero aliasing probability of Logic Built-In-Self-Test (LBIST). In this paper, we present two methods for modifying LBIST to prevent such an attack. The first method makes test patterns dependent on a configurable key which is programed into a chip after the manufacturing stage. The second method uses a remote test management system which can execute LBIST using a different set of test patterns at each test cycle.

Shohreh Sharif Mansouri, Elena Dubrova

One of the most common types of Physical Unclonable Functions (PUFs) is the ring oscillator PUF (RO-PUF), in which the output bits are obtained by comparing the oscillation frequencies of different ring oscillators. In this paper we design a new type of ring oscillator PUF in which the different inverters composing the ring oscillators can be supplied by different voltages. The new RO-PUF can be used to (1) increase the maximum number of possible challenge/response pairs produced by the PUF; (2) generate a high number of bits while consuming a low area; (3) improve the reliability of the PUF in case of temperature variations. We present the basic idea of the new RO-PUF and then discuss its applications.