Secret Key Leakage from Public Key Perturbation of DLP-based Cryptosystems

Finding efficient countermeasures for cryptosystems against fault attacks is challenged by a constant discovery of flaws in designs. Even elements, such as public keys, that do not seem critical must be protected. From the attacks against RSA, we develop a new attack of DLP-based cryptosystems, built in addition on a lattice analysis to recover DSA public keys from partially known nonces. Based on a realistic fault model, our attack only requires 16 faulty signatures to recover a 160-bit DSA secret key within a few minutes on a standard PC. These results significantly improves the previous public element fault attack in the context of DLP-based cryptosystems

Envisioning the Future of Cyber Security in Post-Quantum Era: A Survey on PQ Standardization, Applications, Challenges and Opportunities

The rise of quantum computers exposes vulnerabilities in current public key cryptographic protocols, necessitating the development of secure post-quantum (PQ) schemes. Hence, we conduct a comprehensive study on various PQ approaches, covering the constructional design, structural vulnerabilities, and offer security assessments, implementation evaluations, and a particular focus on side-channel attacks. We analyze global standardization processes, evaluate their metrics in relation to real-world applications, and primarily focus on standardized PQ schemes, selected additional signature competition candidates, and PQ-secure cutting-edge schemes beyond standardization. Finally, we present visions and potential future directions for a seamless transition to the PQ era

Cryptanalysis and Secure Implementation of Modern Cryptographic Algorithms

Cryptanalytic attacks can be divided into two classes: pure mathematical attacks and Side Channel Attacks (SCAs). Pure mathematical attacks are traditional cryptanalytic techniques that rely on known or chosen input-output pairs of the cryptographic function and exploit the inner structure of the cipher to reveal the secret key information. On the other hand, in SCAs, it is assumed that attackers have some access to the cryptographic device and can gain some information from its physical implementation. Cold-boot attack is a SCA which exploits the data remanence property of Random Access Memory (RAM) to retrieve its content which remains readable shortly after its power has been removed. Fault analysis is another example of SCAs in which the attacker is assumed to be able to induce faults in the cryptographic device and observe the faulty output. Then, by careful inspection of faulty outputs, the attacker recovers the secret information, such as secret inner state or secret key. Scan-based Design-For-Test (DFT) is a widely deployed technique for testing hardware chips. Scan-based SCAs exploit the information obtained by analyzing the scanned data in order to retrieve secret information from cryptographic hardware devices that are designed with this testability feature. In the first part of this work, we investigate the use of an off-the-shelf SAT solver, CryptoMinSat, to improve the key recovery of the Advance Encryption Standard (AES-128) key schedules from its corresponding decayed memory images which can be obtained using cold-boot attacks. We also present a fault analysis on both NTRUEncrypt and NTRUSign cryptosystems. For this specific original instantiation of the NTRU encryption system with parameters $(N,p,q)$, our attack succeeds with probability $\approx 1-\frac{1}{p}$ and when the number of faulted coefficients is upper bounded by $t$, it requires $O((pN)^t)$ polynomial inversions in $\mathbb Z/p\mathbb Z[x]/(x^{N}-1)$. We also investigate several techniques to strengthen hardware implementations of NTRUEncrypt against this class of attacks. For NTRUSign with parameters ($N$, $q=p^l$, $\mathcal{B}$, \emph{standard}, $\mathcal{N}$), when the attacker is able to skip the norm-bound signature checking step, our attack needs one fault to succeed with probability $\approx 1-\frac{1}{p}$ and requires $O((qN)^t)$ steps when the number of faulted polynomial coefficients is upper bounded by $t$. The attack is also applicable to NTRUSign utilizing the \emph{transpose} NTRU lattice but it requires double the number of fault injections. Different countermeasures against the proposed attack are also investigated. Furthermore, we present a scan-based SCA on NTRUEncrypt hardware implementations that employ scan-based DFT techniques. Our attack determines the scan chain structure of the polynomial multiplication circuits used in the decryption algorithm which allows the cryptanalyst to efficiently retrieve the secret key. Several key agreement schemes based on matrices were recently proposed. For example, \'{A}lvarez \emph{et al.} proposed a scheme in which the secret key is obtained by multiplying powers of block upper triangular matrices whose elements are defined over $\mathbb{Z}_p$. Climent \emph{et al.} identified the elements of the endomorphisms ring $End(\mathbb{Z}_p \times \mathbb{Z}_{p^2})$ with elements in a set, $E_p$, of matrices of size $2\times 2$, whose elements in the first row belong to $\mathbb{Z}_{p}$ and the elements in the second row belong to $\mathbb{Z}_{p^2}$. Keith Salvin presented a key exchange protocol using matrices in the general linear group, $GL(r,\mathbb{Z}_n)$, where $n$ is the product of two distinct large primes. The system is fully specified in the US patent number 7346162 issued in 2008. In the second part of this work, we present mathematical cryptanalytic attacks against these three schemes and show that they can be easily broken for all practical choices of their security parameters

Tamper-Resistant Arithmetic for Public-Key Cryptography

Cryptographic hardware has found many uses in many ubiquitous and pervasive security devices with a small form factor, e.g. SIM cards, smart cards, electronic security tokens, and soon even RFIDs. With applications in banking, telecommunication, healthcare, e-commerce and entertainment, these devices use cryptography to provide security services like authentication, identification and confidentiality to the user. However, the widespread adoption of these devices into the mass market, and the lack of a physical security perimeter have increased the risk of theft, reverse engineering, and cloning. Despite the use of strong cryptographic algorithms, these devices often succumb to powerful side-channel attacks. These attacks provide a motivated third party with access to the inner workings of the device and therefore the opportunity to circumvent the protection of the cryptographic envelope. Apart from passive side-channel analysis, which has been the subject of intense research for over a decade, active tampering attacks like fault analysis have recently gained increased attention from the academic and industrial research community. In this dissertation we address the question of how to protect cryptographic devices against this kind of attacks. More specifically, we focus our attention on public key algorithms like elliptic curve cryptography and their underlying arithmetic structure. In our research we address challenges such as the cost of implementation, the level of protection, and the error model in an adversarial situation. The approaches that we investigated all apply concepts from coding theory, in particular the theory of cyclic codes. This seems intuitive, since both public key cryptography and cyclic codes share finite field arithmetic as a common foundation. The major contributions of our research are (a) a generalization of cyclic codes that allow embedding of finite fields into redundant rings under a ring homomorphism, (b) a new family of non-linear arithmetic residue codes with very high error detection probability, (c) a set of new low-cost arithmetic primitives for optimal extension field arithmetic based on robust codes, and (d) design techniques for tamper resilient finite state machines

Fault attacks on RSA and elliptic curve cryptosystems

This thesis answered how a fault attack targeting software used to program EEPROM can threaten hardware devices, for instance IoT devices. The successful fault attacks proposed in this thesis will certainly warn designers of hardware devices of the security risks their devices may face on the programming leve

Location Privacy-Preserving Strategies for Secondary Spectrum Use

The scarcity of wireless spectrum resources and the overwhelming demand for wireless broadband resources have prompted industry, government agencies and academia within the wireless communities to develop and come up with effective solutions that can make additional spectrum available for broadband data. As part of these ongoing efforts, cognitive radio networks (CRNs) have emerged as an essential technology for enabling and promoting dynamic spectrum access and sharing, a paradigm primarily aimed at addressing the spectrum scarcity and shortage challenges by permitting and enabling unlicensed or secondary users (SUs) to freely search, locate and exploit unused licensed spectrum opportunities. Despite their great potentials for improving spectrum utilization efficiency and for addressing the spectrum shortage problem, CRNs suffer from serious location privacy issues, which essentially tend to disclose the location information of the SUs to other system entities during their usage of these open spectrum opportunities. Knowing that their whereabouts may be exposed, SUs can be discouraged from joining and participating in the CRNs, potentially hindering the adoption and deployment of this technology. In this thesis, we propose frameworks that are suitable for CRNs, but also preserve the location privacy information of these SU s. More specifically, 1. We propose location privacy-preserving protocols that protect the location privacy of SUs in cooperative sensing-based CRNs while allowing the SUs to perform their spectrum sensing tasks reliably and effectively. Our proposed protocols allow also the detection of malicious user activities through the adoption of reputation mechanisms. 2. We propose location privacy-preserving approaches that provide information-theoretic privacy to SU s’ location in database-driven CRNs through the exploitation of the structured nature of spectrum databases and the fact that database-driven CRNs, by design, rely on multiple spectrum databases. 3. We propose a trustworthy framework for new generation of spectrum access systems in the 3.5 GHz band that not only protects SUs’ privacy, but also ensures that they comply with the unique system requirements, while allowing the detection of misbehaving users

Analysis of BCNS and Newhope Key-exchange Protocols

Lattice-based cryptographic primitives are believed to offer resilience against attacks by quantum computers. Following increasing interest from both companies and government agencies in building quantum computers, a number of works have proposed instantiations of practical post-quantum key-exchange protocols based on hard problems in lattices, mainly based on the Ring Learning With Errors (R-LWE) problem. In this work we present an analysis of Ring-LWE based key-exchange mechanisms and compare two implementations of Ring-LWE based key-exchange protocol: BCNS and NewHope. This is important as NewHope protocol implementation outperforms state-of-the art elliptic curve based Diffie-Hellman key-exchange X25519, thus showing that using quantum safe key-exchange is not only a viable option but also a faster one. Specifically, this thesis compares different reconciliation methods, parameter choices, noise sampling algorithms and performance

A secure architecture enabling end-user privacy in the context of commercial wide-area location-enhanced web services

Mobile location-based services have raised privacy concerns amongst mobile phone users who may need to supply their identity and location information to untrustworthy third parties in order to access these applications. Widespread acceptance of such services may therefore depend on how privacy sensitive information will be handled in order to restore users’ confidence in what could become the “killer app” of 3G networks. The work reported in this thesis is part of a larger project to provide a secure architecture to enable the delivery of location-based services over the Internet. The security of transactions and in particular the privacy of the information transmitted has been the focus of our research. In order to protect mobile users’ identities, we have designed and implemented a proxy-based middleware called the Orient Platform together with its Orient Protocol, capable of translating their real identity into pseudonyms. In order to protect users’ privacy in terms of location information, we have designed and implemented a Location Blurring algorithm that intentionally downgrades the quality of location information to be used by location-based services. The algorithm takes into account a blurring factor set by the mobile user at her convenience and blurs her location by preventing real-time tracking by unauthorized entities. While it penalizes continuous location tracking, it returns accurate and reliable information in response to sporadic location queries. Finally, in order to protect the transactions and provide end-to-end security between all the entities involved, we have designed and implemented a Public Key Infrastructure based on a Security Mediator (SEM) architecture. The cryptographic algorithms used are identitybased, which makes digital certificate retrieval, path validation and revocation redundant in our environment. In particular we have designed and implemented a cryptographic scheme based on Hess’ work [108], which represents, to our knowledge, the first identity-based signature scheme in the SEM setting. A special private key generation process has also been developed in order to enable entities to use a single private key in conjunction with multiple pseudonyms, which significantly simplifies key management. We believe our approach satisfies the security requirements of mobile users and can help restore their confidence in location-based services