Compact Field Programmable Gate Array Based Physical Unclonable Functions Circuits

The Physical Unclonable Functions (PUFs) is a candidate to provide a secure solid root source for identification and authentication applications. It is precious for FPGA-based systems, as FPGA designs are vulnerable to IP thefts and cloning. Ideally, the PUFs should have strong random variations from one chip to another, and thus each PUF is unique and hard to replicate. Also, the PUFs should be stable over time so that the same challenge bits always yield the same result. Correspondingly, one of the major challenges for FPGA-based PUFs is the difficulty of avoiding systematic bias in the integrated circuits but also pulling out consistent characteristics as the PUF at the same time. This thesis discusses several compact PUF structures relying on programmable delay lines (PDLs) and our novel intertwined programmable delays (IPD). We explore the strategy to extract the genuinely random PUF from these structures by minimizing the systematic biases. Yet, our methods still maintain very high reliability. Furthermore, our proposed designs, especially the TERO-based PUFs, show promising resilience to machine learning (ML) attacks. We also suggest the bit-bias metric to estimate PUF’s complexity quickly

A PUF based on transient effect ring oscillator and insensitive to locking phenomenon

International audienceThis paper presents a new silicon physical unclonable function (PUF) based on a transient effect ring oscillator (TERO). The proposed PUF has state of the art PUF characteristics with a good ratio of PUF response variability to response length. Unlike RO-PUF, it is not sensitive to the locking phenomenon, which challenges the use of ring oscillators for the design of both PUF and TRNG. The novel architecture using differential structures guarantees high stability of the TERO-PUF. The area of the TERO-PUF is relatively high, but is still comparable with other PUF designs. However, since the same piece of hardware can be used for both PUF and random number generation, the proposed principle offers an interesting low area mixed solution

Modélisation et caractérisation des fonctions non clonables physiquement

Physically Unclonable Functions, or PUFs, are innovative technologies devoted to solve some security and identification issues. Similarly to a human fingerprint, PUFs allows to identify uniquely electronic devices as they produce an instance-specific signature. Applications as authentication or key generation can take advantage of this embedded function. The main property that we try to obtain from a PUF is the generation of a unique response that varies randomly from one physical device to another without allowing its prediction. Another important property of these PUF is to always reproduce the same response for the same input challenge even in a changing environment. Moreover, the PUF system should be secure against attacks that could reveal its response. In this thesis, we are interested in silicon PUF which take advantage of inherent process variations during the manufacturing of CMOS integrated circuits. We present several PUF constructions, discuss their properties and the implementation techniques to use them in security applications. We first present two novel PUF structures. The first one, called “Loop PUF” is a delay based PUF which relies on the comparison of delay measurements of identical serial delay chains. The major contribution brought by the use of this structure is its implementation simplicity on both ASIC and FPGA platforms, and its flexibility as it can be used for reliable authentication or key generation. The second proposed structure is a ring-oscillator based PUF cells “TERO PUF”. It exploits the oscillatory metastability of cross-coupled elements, and can also be used as True Random Number Generator (TRNG). More precisely, the PUF response takes advantage from the introduced oscillatory metastability of an SR flip-flop when the S and R inputs are connected to the same input signal. Experimental results show the high performance of these two proposed PUF structures. Second, in order to fairly compare the quality of different delay based PUFs, we propose a specific characterization method. It is based on statistical measurements on basic delay elements. The main benefit of this method is that it allows the designer to be sure that the PUF will meet the expected performances before its implementation and fabrication. Finally, Based on the unclonability and unpredictability properties of the PUFs, we present new techniques to perform “loop PUF” authentication and cryptographic key generation. Theoretical and experimental results show the efficiency of the introduced techniques in terms of complexity and reliabilityLes fonctions non clonables physiquement, appelées PUF (Physically Unclonable Functions), représentent une technologie innovante qui permet de résoudre certains problèmes de sécurité et d’identification. Comme pour les empreintes humaines, les PUF permettent de différencier des circuits électroniques car chaque exemplaire produit une signature unique. Ces fonctions peuvent être utilisées pour des applications telles que l’authentification et la génération de clés cryptographiques. La propriété principale que l’on cherche à obtenir avec les PUF est la génération d’une réponse unique qui varie de façon aléatoire d’un circuit à un autre, sans la possibilité de la prédire. Une autre propriété de ces PUF est de toujours reproduire, quel que soit la variation de l’environnement de test, la même réponse à un même défi d’entrée. En plus, une fonction PUF doit être sécurisée contre les attaques qui permettraient de révéler sa réponse. Dans cette thèse, nous nous intéressons aux PUF en silicium profitant des variations inhérentes aux technologies de fabrication des circuits intégrés CMOS. Nous présentons les principales architectures de PUF, leurs propriétés, et les techniques mises en œuvre pour les utiliser dans des applications de sécurité. Nous présentons d’abord deux nouvelles structures de PUF. La première structure appelée “Loop PUF” est basée sur des chaînes d’éléments à retard contrôlés. Elle consiste à comparer les délais de chaînes à retard identiques qui sont mises en série. Les points forts de cette structure sont la facilité de sa mise en œuvre sur les deux plates-formes ASIC et FPGA, la grande flexibilité pour l’authentification des circuits intégrés ainsi que la génération de clés de chiffrement. La deuxième structure proposée “TERO PUF” est basée sur le principe de cellules temporairement oscillantes. Elle exploite la métastabilité oscillatoire d’éléments couplés en croix, et peut aussi être utilisée pour un générateur vrai d’aléas (TRNG). Plus précisément, la réponse du PUF profite de la métastabilité oscillatoire introduite par une bascule SR lorsque les deux entrées S et R sont connectées au même signal d’entrée. Les résultats expérimentaux montrent le niveau de performances élevé des deux structures de PUF proposées. Ensuite, afin de comparer équitablement la qualité des différentes PUF à retard, nous proposons une méthode de caractérisation spécifique. Elle est basée sur des mesures statistiques des éléments à retard. Le principal avantage de cette méthode vient de sa capacité à permettre au concepteur d’être sûr que la fonction PUF aura les performances attendues avant sa mise en œuvre et sa fabrication. Enfin, en se basant sur les propriétés de non clonabilité et de l’imprévisibilité des PUF, nous présentons de nouvelles techniques d’authentification et de génération de clés de chiffrement en utilisant la “loop PUF” proposée. Les résultats théoriques et expérimentaux montrent l’efficacité des techniques introduites en termes de complexité et de fiabilit

Energy Harvesting and Sensor Based Hardware Security Primitives for Cyber-Physical Systems

The last few decades have seen a large proliferation in the prevalence of cyber-physical systems. Although cyber-physical systems can offer numerous advantages to society, their large scale adoption does not come without risks. Internet of Things (IoT) devices can be considered a significant component within cyber-physical systems. They can provide network communication in addition to controlling the various sensors and actuators that exist within the larger cyber-physical system. The adoption of IoT features can also provide attackers with new potential avenues to access and exploit a system\u27s vulnerabilities. Previously, existing systems could more or less be considered a closed system with few potential points of access for attackers. Security was thus not typically a core consideration when these systems were originally designed. The cumulative effect is that these systems are now vulnerable to new security risks without having native security countermeasures that can easily address these vulnerabilities. Even just adding standard security features to these systems is itself not a simple task. The devices that make up these systems tend to have strict resource constraints in the form of power consumption and processing power. In this dissertation, we explore how security devices known as Physically Unclonable Functions (PUFs) could be used to address these concerns. PUFs are a class of circuits that are unique and unclonable due to inherent variations caused by the device manufacturing process. We can take advantage of these PUF properties by using the outputs of PUFs to generate secret keys or pseudonyms that are similarly unique and unclonable. Existing PUF designs are commonly based around transistor level variations in a special purpose integrated circuit (IC). Integrating these designs within a system would still require additional hardware along with system modification to interact with the device. We address these concerns by proposing a novel PUF design methodology for the creation of PUFs whose integration within these systems would minimize the cost of redesigning the system by reducing the need to add additional hardware. This goal is achieved by creating PUF designs from components that may already exist within these systems. A PUF designed from existing components creates the possibility of adding a PUF (and thus security features) to the system without actually adding any additional hardware. This could allow PUFs to become a more attractive security option for integration with resource constrained devices. Our proposed approach specifically targets sensors and energy harvesting devices since they can provide core functions within cyber-physical systems such as power generation and sensing capabilities. These components are known to exhibit variations due to the manufacturing process and could thus be utilized to design a PUF. Our first contribution is the proposal of a novel PUF design methodology based on using components which are already commonly found within cyber-physical systems. The proposed methodology uses eight sensors or energy harvesting devices along with a microcontroller. It is unlikely that single type of sensor or energy harvester will exist in all possible cyber-physical systems. Therefore, it is important to create a range of designs in order to reach a greater portion of cyber-physical systems. The second contribution of this work is the design of a PUF based on piezo sensors. Our third contribution is the design of a PUF that utilizes thermistor temperature sensors. The fourth contribution of this work is a proposed solar cell based PUF design. Furthermore, as a fifth contribution of this dissertation we evaluate a selection of common solar cell materials to establish which type of solar cell would be best suited to the creation of a PUF based on the operating conditions. The viability of the proposed designs is evaluated through testing in terms of reliability and uniformity. In addition, Monte Carlo simulations are performed to evaluate the uniqueness property of the designs. For our final contribution we illustrate the security benefits that can be achieved through the adoption of PUFs by cyber-physical systems. For this purpose we chose to highlight vehicles since they are a very popular example of a cyber-physical system and they face unique security challenges which are not readily solvable by standard solutions. Our contribution is the proposal of a novel controller area network (CAN) security framework that is based on PUFs. The framework does not require any changes to the underlying CAN protocol and also minimizes the amount of additional message passing overhead needed for its operation. The proposed framework is a good example of how the cost associated with implementing such a framework could be further reduced through the adoption of our proposed PUF designs. The end result is a method which could introduce security to an inherently insecure system while also making its integration as seamless as possible by attempting to minimize the need for additional hardware