Interpose PUF can be PAC Learned

In this work, we prove that Interpose PUF is learnable in the PAC model. First, we show that Interpose PUF can be approximated by a Linear Threshold Function~(LTF), assuming the interpose bit to be random. We translate the randomness in the interpose bit to classification noise of the hypothesis. Using classification noise model, we prove that the resultant LTF can be learned with number of labelled examples~(challenge response pairs) polynomial in the number of stages and PAC model parameters

Learnability of Multiplexer PUF and SNS_N-PUF : A Fourier-based Approach

In this work, we prove that Multiplexer PUF~(MPUF) and $S_N$-PUF are learnable in the PAC model. First, we show that both the designs can be represented as a function of Linear Threshold Functions. We show that the noise sensitivity of $(n,k)$-MPUF and $S_N$-PUF can be bounded by $O(2^{k} \sqrt{\epsilon})$ and $O(N\sqrt{\epsilon})$ respectively. Finally, we show that as a result of bounded noise sensitivity, both the designs can be accurately approximated using low degree algorithm. Also, the number of labelled examples~(challenge-response pairs) required by the algorithm is polynomial in the input length and PAC model parameters

PAC Learnability of iPUF Variants

Interpose PUF~(iPUF) is a strong PUF construction that was shown to be vulnerable against empirical machine learning as well as PAC learning attacks. In this work, we extend the PAC Learning results of Interpose PUF to prove that the variants of iPUF are also learnable in the PAC model under the Linear Threshold Function representation class

Physically Related Functions: A New Paradigm for Light-weight Key-Exchange

In this paper, we propose a novel concept named Physically Related Function(PReF) which are devices with hardware roots of trust. It enables secure key-exchange with no pre-established/embedded secret keys. This work is motivated by the need to perform key-exchange between lightweight resource-constrained devices. We present a proof-of-concept realization of our contributions in hardware using FPGAs

PUF-COTE: A PUF Construction with Challenge Obfuscation and Throughput Enhancement

Physically Unclonable Functions~(PUFs) have been a potent choice for enabling low-cost, secure communication. However, the state-of-the-art strong PUFs generate single-bit response. So, we propose PUF-COTE: a high throughput architecture based on linear feedback shift register and a strong PUF as the ``base\u27\u27-PUF. At the same time, we obfuscate the challenges to the ``base\u27\u27-PUF of the final construction. We experimentally evaluate the quality of the construction by implementing it on Artix 7 FPGAs. We evaluate the statistical quality of the responses~(using NIST SP800-92 test suit and standard PUF metrics: uniformity, uniqueness, reliability, strict avalanche criterion, ML-based modelling), which is a crucial factor for cryptographic applications

Systematically Quantifying Cryptanalytic Non-Linearities in Strong PUFs

Physically Unclonable Functions~(PUFs) with large challenge space~(also called Strong PUFs) are promoted for usage in authentications and various other cryptographic and security applications. In order to qualify for these cryptographic applications, the Boolean functions realized by PUFs need to possess a high non-linearity~(NL). However, with a large challenge space~(usually $\geq 64$ bits), measuring NL by classical techniques like Walsh transformation is computationally infeasible. In this paper, we propose the usage of a heuristic-based measure called non-homomorphicity test which estimates the NL of Boolean functions with high accuracy in spite of not needing access to the entire challenge-response set. We also combine our analysis with a technique used in linear cryptanalysis, called Piling-up lemma, to measure the NL of popular PUF compositions. As a demonstration to justify the soundness of the metric, we perform extensive experimentation by first estimating the NL of constituent Arbiter/Bistable Ring PUFs using the non-homomorphicity test, and then applying them to quantify the same for their XOR compositions namely XOR Arbiter PUFs and XOR Bistable Ring PUF. Our findings show that the metric explains the impact of various parameter choices of these PUF compositions on the NL obtained and thus promises to be used as an important objective criterion for future efforts to evaluate PUF designs. While the framework is not representative of the machine learning robustness of PUFs, it can be a useful complementary tool to analyze the cryptanalytic strengths of PUF primitives

Harmonizing PUFs for Forward Secure Authenticated Key Exchange with Symmetric Primitives

Physically Unclonable Functions (PUFs) have been a potent choice for enabling low-cost, secure communication. However, in most applications, one party holds the PUF, and the other securely stores the challenge-response pairs (CRPs). It does not remove the need for secure storage entirely, which is one of the goals of PUFs. This paper proposes a PUF-based construction called Harmonizing PUFs (\textsf{H_PUF}s), allowing two independent PUFs to generate the same outcome without storing any confidential data. As an application of \textsf{H_PUF} construction, we present $\textsf{H-AKE}$: a low-cost authenticated key exchange protocol for resource-constrained nodes that is secure against replay and impersonation attacks. The novelty of the protocol is that it achieves forward secrecy without requiring to perform asymmetric group operations like elliptic curve scalar multiplications underlying traditional key-exchange techniques

Teachers’ professional learning during and after Covid: A role for open digital badges

This report examines how open digital badges could support successful Teacher Professional Development (TPD) at scale. We present insight from two one-day events attended by practitioners and senior educational leaders in India and two pilot interventions that integrated digital badges into courses developed in response to the Covid-19 pandemic. TPD gives teachers the opportunity to improve, adapt and innovate their classroom practice and never has it been more critical than in helping shape the educational and societal response to recent global disruptions. In many countries, such as India where our study is based, digital badges are little used in TPD, so this study makes an important contribution to understanding the perception and value attached to digital badges and in supporting discussions that frame emerging narratives and practice. A knowledge exchange partnership of academics from The Open University, UK (OU) and Tata Institute of Social Sciences, India (TISS) supported by GCRF funding has been instrumental in delivering the activities and findings discussed

A successful pregnancy occurred after isolating the offending antibody(s) and choosing appropriate sperm donor of similar phenotype

Sensitization against Rh(D )is the most common cause of haemolytic disease of fetus and newborn (HDFN). Now a days, a widespread use of antenatal and postnatal Rh immunoglobulin has resulted in marked decrease in prevalence of Rh(D) alloimmunization. Fetal loss due to other red cell antigens gain importance as there are no prophylactic immunoglobulin are available. Here, we present a case of primary infertility associated with non Rh(D) alloimmunization which was detected in a 30 year old housewife during her ongoing infertility treatment. The antibody identification workup showed patient is having multiple alloantibodies , probable anti-c, and anti-Fya. The extended phenotype shows that the husband is mismatched with the wife's phenotype in “c” and Fya. Also the probable antibody in the mother's serum are anti-c and anti-Fya which are noted to cause HDFN as per literature