A formal definition and a new security mechanism of physical unclonable functions

The characteristic novelty of what is generally meant by a "physical unclonable function" (PUF) is precisely defined, in order to supply a firm basis for security evaluations and the proposal of new security mechanisms. A PUF is defined as a hardware device which implements a physical function with an output value that changes with its argument. A PUF can be clonable, but a secure PUF must be unclonable. This proposed meaning of a PUF is cleanly delineated from the closely related concepts of "conventional unclonable function", "physically obfuscated key", "random-number generator", "controlled PUF" and "strong PUF". The structure of a systematic security evaluation of a PUF enabled by the proposed formal definition is outlined. Practically all current and novel physical (but not conventional) unclonable physical functions are PUFs by our definition. Thereby the proposed definition captures the existing intuition about what is a PUF and remains flexible enough to encompass further research. In a second part we quantitatively characterize two classes of PUF security mechanisms, the standard one, based on a minimum secret read-out time, and a novel one, based on challenge-dependent erasure of stored information. The new mechanism is shown to allow in principle the construction of a "quantum-PUF", that is absolutely secure while not requiring the storage of an exponentially large secret. The construction of a PUF that is mathematically and physically unclonable in principle does not contradict the laws of physics.Comment: 13 pages, 1 figure, Conference Proceedings MMB & DFT 2012, Kaiserslautern, German

A new Definition and Classification of Physical Unclonable Functions

A new definition of "Physical Unclonable Functions" (PUFs), the first one that fully captures its intuitive idea among experts, is presented. A PUF is an information-storage system with a security mechanism that is 1. meant to impede the duplication of a precisely described storage-functionality in another, separate system and 2. remains effective against an attacker with temporary access to the whole original system. A novel classification scheme of the security objectives and mechanisms of PUFs is proposed and its usefulness to aid future research and security evaluation is demonstrated. One class of PUF security mechanisms that prevents an attacker to apply all addresses at which secrets are stored in the information-storage system, is shown to be closely analogous to cryptographic encryption. Its development marks the dawn of a new fundamental primitive of hardware-security engineering: cryptostorage. These results firmly establish PUFs as a fundamental concept of hardware security.Comment: 6 pages, 3 figures; Proceedings "CS2 '15 Proceedings of the Second Workshop on Cryptography and Security in Computing Systems", Amsterdam, 2015, ACM Digital Librar

Evaluation of PUF and QKD integration techniques as root of trust in communication systems

Quantum Cryptography could be the next key technology in terms of secure communication, but, as with every new technology, it presents problems that need to be solved in order to become a reality in daily life. This work discusses the integration of Physical Unclonable Functions (PUFs) as a solution for the authentication of the endpoints in quantum communication protocols. The use of PUF constructions would allow the authentication of devices without the need of relying on third parties, and support switched trustworthy quantum communication channels; two unseen features in Quantum Key Distribution (QKD) until now. We analyze in detail PUF integration within the BB84 protocol, as it is the foundation for all QKD protocols, and two proposals for an authentication scheme are made, depending on the connection characteristics of the communication endpoints and the distance between them. These proposals are then generalized for other types of QKD protocol. Moreover, different types of PUF are analyzed to conclude which ones are the most suitable for our purpose.La Criptografía Cuántica podría ser la próxima tecnología clave en relación a la seguridad de las comunicaciones pero, como toda nueva tecnología, presenta problemas que deben ser resueltos antes de llegar a ser una realidad en el día a día. Este trabajo discute la integración de Funciones Físicas No-Clonables (PUFs, por sus siglas en inglés) como solución a la autenticación de los extremos en un protocolo de comunicación cuántica. El uso de PUFs permitiría la autenticación de dispositivos sin necesidad de depender de terceros, además de abrir la posibilidad a la conmutación de canales de comunicación cuántica; dos características nunca vistas en la Distribución Cuántica de Claves (QKD, por sus siglas en inglés) hasta ahora. Se analiza en detalle la integración de PUFs en el protocolo BB84, ya que es la base de todos los protocolos de QKD, y se proponen dos esquemas de autenticación distintos, atendiendo a las características de los extremos de la comunicación y la distancia entre ellos. Después, estas propuestas se generalizan para el resto de protocolos de QKD. Además, se estudian distintos tipos de PUF con el objeto de encontrar la más adecuada para nuestro propósito.Universidad de Sevilla. Grado en Físic

Roadmap on optical security

Postprint (author's final draft

Authenticated communication from quantum readout of PUFs

Quantum readout of physical unclonable functions (PUFs) is a recently introduced method for remote authentication of objects. We present an extension of the protocol to enable the authentication of data: A verifier can check if received classical data were sent by the PUF holder. We call this modification QR-d or, in the case of the optical-PUF implementation, QSA-d. We discuss how QSA-d can be operated in a parallel way. We also present a protocol for authenticating quantum states.</p

Optical Systems Identification through Rayleigh Backscattering

: We introduce a technique to generate and read the digital signature of the networks, channels, and optical devices that possess the fiber-optic pigtails to enhance physical layer security (PLS). Attributing a signature to the networks or devices eases the identification and authentication of networks and systems thus reducing their vulnerability to physical and digital attacks. The signatures are generated using an optical physical unclonable function (OPUF). Considering that OPUFs are established as the most potent anti-counterfeiting tool, the created signatures are robust against malicious attacks such as tampering and cyber attacks. We investigate Rayleigh backscattering signal (RBS) as a strong OPUF to generate reliable signatures. Contrary to other OPUFs that must be fabricated, the RBS-based OPUF is an inherent feature of fibers and can be easily obtained using optical frequency domain reflectometry (OFDR). We evaluate the security of the generated signatures in terms of their robustness against prediction and cloning. We demonstrate the robustness of signatures against digital and physical attacks confirming the unpredictability and unclonability features of the generated signatures. We explore signature cyber security by considering the random structure of the produced signatures. To demonstrate signature reproducibility through repeated measurements, we simulate the signature of a system by adding a random Gaussian white noise to the signal. This model is proposed to address services including security, authentication, identification, and monitoring

Quantum Physical Unclonable Functions: Possibilities and Impossibilities

A Physical Unclonable Function (PUF) is a device with unique behaviour that is hard to clone hence providing a secure fingerprint. A variety of PUF structures and PUF-based applications have been explored theoretically as well as being implemented in practical settings. Recently, the inherent unclonability of quantum states has been exploited to derive the quantum analogue of PUF as well as new proposals for the implementation of PUF. We present the first comprehensive study of quantum Physical Unclonable Functions (qPUFs) with quantum cryptographic tools. We formally define qPUFs, encapsulating all requirements of classical PUFs as well as introducing a new testability feature inherent to the quantum setting only. We use a quantum game-based framework to define different levels of security for qPUFs: quantum exponential unforgeability, quantum existential unforgeability and quantum selective unforgeability. We introduce a new quantum attack technique based on the universal quantum emulator algorithm of Marvin and Lloyd to prove no qPUF can provide quantum existential unforgeability. On the other hand, we prove that a large family of qPUFs (called unitary PUFs) can provide quantum selective unforgeability which is the desired level of security for most PUF-based applications.Comment: 32 pages including the appendi

Quantum Lock: A Provable Quantum Communication Advantage

Physical unclonable functions(PUFs) provide a unique fingerprint to a physical entity by exploiting the inherent physical randomness. Gao et al. discussed the vulnerability of most current-day PUFs to sophisticated machine learning-based attacks. We address this problem by integrating classical PUFs and existing quantum communication technology. Specifically, this paper proposes a generic design of provably secure PUFs, called hybrid locked PUFs(HLPUFs), providing a practical solution for securing classical PUFs. An HLPUF uses a classical PUF(CPUF), and encodes the output into non-orthogonal quantum states to hide the outcomes of the underlying CPUF from any adversary. Here we introduce a quantum lock to protect the HLPUFs from any general adversaries. The indistinguishability property of the non-orthogonal quantum states, together with the quantum lockdown technique prevents the adversary from accessing the outcome of the CPUFs. Moreover, we show that by exploiting non-classical properties of quantum states, the HLPUF allows the server to reuse the challenge-response pairs for further client authentication. This result provides an efficient solution for running PUF-based client authentication for an extended period while maintaining a small-sized challenge-response pairs database on the server side. Later, we support our theoretical contributions by instantiating the HLPUFs design using accessible real-world CPUFs. We use the optimal classical machine-learning attacks to forge both the CPUFs and HLPUFs, and we certify the security gap in our numerical simulation for construction which is ready for implementation.Comment: Replacement of paper "Hybrid PUF: A Novel Way to Enhance the Security of Classical PUFs" (arXiv:2110.09469