127 research outputs found
Towards trustworthy computing on untrustworthy hardware
Historically, hardware was thought to be inherently secure and trusted due to its
obscurity and the isolated nature of its design and manufacturing. In the last two
decades, however, hardware trust and security have emerged as pressing issues.
Modern day hardware is surrounded by threats manifested mainly in undesired
modifications by untrusted parties in its supply chain, unauthorized and pirated
selling, injected faults, and system and microarchitectural level attacks. These threats,
if realized, are expected to push hardware to abnormal and unexpected behaviour
causing real-life damage and significantly undermining our trust in the electronic and
computing systems we use in our daily lives and in safety critical applications. A
large number of detective and preventive countermeasures have been proposed in
literature. It is a fact, however, that our knowledge of potential consequences to
real-life threats to hardware trust is lacking given the limited number of real-life
reports and the plethora of ways in which hardware trust could be undermined. With
this in mind, run-time monitoring of hardware combined with active mitigation of
attacks, referred to as trustworthy computing on untrustworthy hardware, is proposed
as the last line of defence. This last line of defence allows us to face the issue of live
hardware mistrust rather than turning a blind eye to it or being helpless once it occurs.
This thesis proposes three different frameworks towards trustworthy computing
on untrustworthy hardware. The presented frameworks are adaptable to different
applications, independent of the design of the monitored elements, based on
autonomous security elements, and are computationally lightweight. The first
framework is concerned with explicit violations and breaches of trust at run-time,
with an untrustworthy on-chip communication interconnect presented as a potential
offender. The framework is based on the guiding principles of component guarding,
data tagging, and event verification. The second framework targets hardware elements
with inherently variable and unpredictable operational latency and proposes a
machine-learning based characterization of these latencies to infer undesired latency
extensions or denial of service attacks. The framework is implemented on a DDR3
DRAM after showing its vulnerability to obscured latency extension attacks. The
third framework studies the possibility of the deployment of untrustworthy hardware
elements in the analog front end, and the consequent integrity issues that might arise
at the analog-digital boundary of system on chips. The framework uses machine
learning methods and the unique temporal and arithmetic features of signals at this
boundary to monitor their integrity and assess their trust level
Correlated Pseudorandomness from the Hardness of Quasi-Abelian Decoding
Secure computation often benefits from the use of correlated randomness to
achieve fast, non-cryptographic online protocols. A recent paradigm put forth
by Boyle (CCS 2018, Crypto 2019) showed how pseudorandom
correlation generators (PCG) can be used to generate large amounts of useful
forms of correlated (pseudo)randomness, using minimal interactions followed
solely by local computations, yielding silent secure two-party computation
protocols (protocols where the preprocessing phase requires almost no
communication). An additional property called programmability allows to extend
this to build N-party protocols. However, known constructions for programmable
PCG's can only produce OLE's over large fields, and use rather new splittable
Ring-LPN assumption.
In this work, we overcome both limitations. To this end, we introduce the
quasi-abelian syndrome decoding problem (QA-SD), a family of assumptions which
generalises the well-established quasi-cyclic syndrome decoding assumption.
Building upon QA-SD, we construct new programmable PCG's for OLE's over any
field with . Our analysis also sheds light on the security
of the ring-LPN assumption used in Boyle (Crypto 2020). Using
our new PCG's, we obtain the first efficient N-party silent secure computation
protocols for computing general arithmetic circuit over for any
.Comment: This is a long version of a paper accepted at CRYPTO'2
Critical Perspectives on Provable Security: Fifteen Years of Another Look Papers
We give an overview of our critiques of âproofsâ of security and a guide to
our papers on the subject that have appeared over the past decade and a half. We also
provide numerous additional examples and a few updates and errata
Quantum Algorithms for Attacking Hardness Assumptions in Classical and PostâQuantum Cryptography
In this survey, the authors review the main quantum algorithms for solving the computational problems that serve as hardness assumptions for cryptosystem. To this end, the authors consider both the currently most widely used classically secure cryptosystems, and the most promising candidates for post-quantum secure cryptosystems. The authors provide details on the cost of the quantum algorithms presented in this survey. The authors furthermore discuss ongoing research directions that can impact quantum cryptanalysis in the future
Survey on Fully Homomorphic Encryption, Theory, and Applications
Data privacy concerns are increasing significantly in the context of Internet of Things, cloud services, edge computing, artificial intelligence applications, and other applications enabled by next generation networks. Homomorphic Encryption addresses privacy challenges by enabling multiple operations to be performed on encrypted messages without decryption. This paper comprehensively addresses homomorphic encryption from both theoretical and practical perspectives. The paper delves into the mathematical foundations required to understand fully homomorphic encryption (FHE). It consequently covers design fundamentals and security properties of FHE and describes the main FHE schemes based on various mathematical problems. On a more practical level, the paper presents a view on privacy-preserving Machine Learning using homomorphic encryption, then surveys FHE at length from an engineering angle, covering the potential application of FHE in fog computing, and cloud computing services. It also provides a comprehensive analysis of existing state-of-the-art FHE libraries and tools, implemented in software and hardware, and the performance thereof
Side-Channel Analysis and Cryptography Engineering : Getting OpenSSL Closer to Constant-Time
As side-channel attacks reached general purpose PCs and started to be more practical for attackers to exploit, OpenSSL adopted in 2005 a flagging mechanism to protect against SCA. The opt-in mechanism allows to flag secret values, such as keys, with the BN_FLG_CONSTTIME flag. Whenever a flag is checked and detected, the library changes its execution flow to SCA-secure functions that are slower but safer, protecting these secret values from being leaked. This mechanism favors performance over security, it is error-prone, and is obscure for most library developers, increasing the potential for side-channel vulnerabilities. This dissertation presents an extensive side-channel analysis of OpenSSL and criticizes its fragile flagging mechanism. This analysis reveals several flaws affecting the library resulting in multiple side-channel attacks, improved cache-timing attack techniques, and a new side channel vector. The first part of this dissertation introduces the main topic and the necessary related work, including the microarchitecture, the cache hierarchy, and attack techniques; then it presents a brief troubled history of side-channel attacks and defenses in OpenSSL, setting the stage for the related publications. This dissertation includes seven original publications contributing to the area of side-channel analysis, microarchitecture timing attacks, and applied cryptography. From an SCA perspective, the results identify several vulnerabilities and flaws enabling protocol-level attacks on RSA, DSA, and ECDSA, in addition to full SCA of the SM2 cryptosystem. With respect to microarchitecture timing attacks, the dissertation presents a new side-channel vector due to port contention in the CPU execution units. And finally, on the applied cryptography front, OpenSSL now enjoys a revamped code base securing several cryptosystems against SCA, favoring a secure-by-default protection against side-channel attacks, instead of the insecure opt-in flagging mechanism provided by the fragile BN_FLG_CONSTTIME flag
A Survey on Exotic Signatures for Post-Quantum Blockchain: Challenges & Research Directions
Blockchain technology provides efficient and secure solutions to various online activities by utilizing a wide range of cryptographic tools. In this paper, we survey the existing literature on post-quantum secure digital signatures that possess exotic advanced features and which are crucial cryptographic tools used in the blockchain ecosystem for (i) account management, (ii) consensus efficiency, (iii) empowering scriptless blockchain, and (iv) privacy. The exotic signatures that we particularly focus on in this work are the following: multi-/aggregate, threshold, adaptor, blind and ring signatures. Herein the term exotic refers to signatures with properties which are not just beyond the norm for signatures e.g. unforgeability, but also imbue new forms of functionalities. Our treatment of such exotic signatures includes discussions on existing challenges and future research directions in the post-quantum space. We hope that this article will help to foster further research to make post-quantum cryptography more accessible so that blockchain systems can be made ready in advance of the approaching quantum threats
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Novel reversible text data de-identification techniques based on native data structures
Technological development in today's digital world has resulted in the collection and storage of large amounts of personal data. These data enable both direct services and non-direct activities, known as secondary use. The secondary use of data can improve decision-making, service experiences, and healthcare systems. However, the widespread reuse of personal data raises significant privacy and policy issues, especially for health- related information; these data may contain sensitive data, leading to privacy breaches if compromised. Legal systems establish laws to protect the privacy of personal data disclosed for secondary use. A well-known example is the General Data Protection Regulation (GDPR), which outlines a specific set of rules for sharing and storing personal data to protect individual privacy. The GDPR explicitly points to data de-identification, especially pseudonymization, as one measure that can help meet the requirements for the processing of personal data.
The literature on privacy preservation approaches has largely been developed in the field of data anonymization, where personal data are irreversibly removed or obfuscated and there is no means by which to recover an individual's identity if needed. By contrast, pseudonymization is a promising technique to protect privacy while enabling the recovery of de-identified data. Significantly, many existing approaches for pseudonymization were developed long before the GDPR requirements were established, and so they may fail to satisfy its provisions. Therefore, it is worthwhile to offer technical solutions to preserve privacy while supporting the legitimate use of data.
This thesis proposes a novel de-identification system for unstructured textual data, known as ARTPHIL, that generates de-identified data in compliance with the GDPR requirement for strong pseudonymization. The system was evaluated using 2014 i2b2 testing data. The proposed system achieved a recall of 96.93% in terms of detecting and encrypting personal health information, as specified under guidelines provided by the Health Insurance Portability and Accountability Act (HIPAA). The system used a novel and lightweight cryptography algorithm E-ART to encrypt personal data cost-effectively and without compromising security. The main novelty of the E-ART algorithm is the use of the reflection property of a balanced binary tree data structure as substitution method instead of complex and multiple iterations. The performance and security of the proposed algorithm were compared to two symmetric encryption algorithms: The Advanced Encryption Standard and Data Encryption Standard. The security analysis showed comparable results, but the performance analysis indicated that EâART had the shortest ciphertext and running time with comparable memory usage, which indicates the feasibility of using ARTPHIL for delay-sensitive or data-intensive application
On Lattice-Based Signatures with Advanced Functionalities
Lattice-based cryptography is a prominent class of cryptographic systems that has been emerged as one of the main candidates replacing classical cryptography in future computing environments such as quantum computing.
Quantum computers exploit quantum mechanical phenomena to solve computational problems, on which the security of currently deployed (classical) cryptographic systems is based.
While these computational problems, e.g., factoring integers and computing discrete logarithms, are intractable for conventional (classical) computers, it is meanwhile known that they can be easily solved on quantum computers (Shor 1997).
However, lattice problems, such as finding short non-zero vectors, seem to withstand attacks having quantum computing power.
In the last two decades we have seen many cryptographic proposals based on lattices.
In particular, lattice-based (ordinary) signature schemes were greatly improved with respect to efficiency and security.
This can be observed from the post-quantum standardization process initiated by the National Institute of Standards and Technology (NIST).
In fact, from the five signature schemes that have been submitted to this process, there are currently three finalists, where two of them are lattice-based submissions.
In this thesis, we are specifically interested in lattice-based signature schemes with advanced functionalities.
In addition to the basic security goals that an ordinary signature scheme ensures, i.e., authentication, non-repudiation, and integrity, these schemes provide features that are application-specific.
While ordinary signature schemes based on lattices are ready to be deployed in practice, this statement cannot be made for lattice-based signature schemes with advanced functionalities.
This thesis makes a significant progress towards deploying the aforementioned type of signature schemes in practice.
With focus on privacy-preserving applications in future computing environments, we particularly facilitate the protection of secret keys in cryptocurrencies such as Bitcoin and Ethereum.
We provide practical solutions to anonymous e-cash, anonymous credentials, smart contracts, and e-voting.
We believe that our techniques can be used to develop further advanced signature schemes to be deployed in other application scenarios.
For instance, in information security systems that perform critical operations such as distributed key generation, anonymization of medical data, and updating reliable routing information
Threshold Kleptographic Attacks on Discrete Logarithm Based Signatures
In an out of threshold scheme, out of members must cooperate to recover a secret. A kleptographic attack is a backdoor which can be implemented in an algorithm and further used to retrieve a user\u27s secret key. We combine the notions of threshold scheme and kleptographic attack to construct the first out of threshold kleptographic attack on discrete logarithm based digital signatures and prove its security in the standard and random oracle models
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