References of "Ryan, Peter 50002965"
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See detailA Proof of Entropy Minimization for Outputs in Deletion Channels via Hidden Word Statistics
Atashpendar, Arash UL; Mestel, David; Roscoe, A.W. (Bill) et al

E-print/Working paper (2018)

From the output produced by a memoryless deletion channel from a uniformly random input of known length n, one obtains a posterior distribution on the channel input. The difference between the Shannon ... [more ▼]

From the output produced by a memoryless deletion channel from a uniformly random input of known length n, one obtains a posterior distribution on the channel input. The difference between the Shannon entropy of this distribution and that of the uniform prior measures the amount of information about the channel input which is conveyed by the output of length m, and it is natural to ask for which outputs this is extremized. This question was posed in a previous work, where it was conjectured on the basis of experimental data that the entropy of the posterior is minimized and maximized by the constant strings 𝟶𝟶𝟶… and 𝟷𝟷𝟷… and the alternating strings 𝟶𝟷𝟶𝟷… and 𝟷𝟶𝟷𝟶… respectively. In the present work we confirm the minimization conjecture in the asymptotic limit using results from hidden word statistics. We show how the analytic-combinatorial methods of Flajolet, Szpankowski and Vall\'ee for dealing with the hidden pattern matching problem can be applied to resolve the case of fixed output length and n→∞, by obtaining estimates for the entropy in terms of the moments of the posterior distribution and establishing its minimization via a measure of autocorrelation. [less ▲]

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See detailCholesteric Liquid Crystal Shells as Enabling Material for Information-Rich Design and Architecture.
Schwartz, Mathew; Lenzini, Gabriele UL; Geng, Yong UL et al

in Advanced Materials (2018)

The responsive and dynamic character of liquid crystals (LCs), arising from their ability to self-organize into long-range ordered structures while maintaining fluidity, has given them a role as key ... [more ▼]

The responsive and dynamic character of liquid crystals (LCs), arising from their ability to self-organize into long-range ordered structures while maintaining fluidity, has given them a role as key enabling materials in the information technology that surrounds us today. Ongoing research hints at future LC-based technologies of entirely different types, for instance by taking advantage of the peculiar behavior of cholesteric liquid crystals (CLCs) subject to curvature. Spherical shells of CLC reflect light omnidirectionally with specific polarization and wavelength, tunable from the UV to the infrared (IR) range, with complex patterns arising when many of them are brought together. Here, these properties are analyzed and explained, and future application opportunities from an inter- disciplinary standpoint are discussed. By incorporating arrangements of CLC shells in smart facades or vehicle coatings, or in objects of high value subject to counterfeiting, game-changing future uses might arise in fields spanning infor- mation security, design, and architecture. The focus here is on the challenges of a digitized and information-rich future society where humans increasingly rely on technology and share their space with autonomous vehicles, drones, and robots. [less ▲]

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See detailFrom Clustering Supersequences to Entropy Minimizing Subsequences for Single and Double Deletions
Atashpendar, Arash UL; Beunardeau, Marc; Connolly, Aisling et al

E-print/Working paper (2018)

A binary string transmitted via a memoryless i.i.d. deletion channel is received as a subsequence of the original input. From this, one obtains a posterior distribution on the channel input, corresponding ... [more ▼]

A binary string transmitted via a memoryless i.i.d. deletion channel is received as a subsequence of the original input. From this, one obtains a posterior distribution on the channel input, corresponding to a set of candidate supersequences weighted by the number of times the received subsequence can be embedded in them. In a previous work it is conjectured on the basis of experimental data that the entropy of the posterior is minimized and maximized by the constant and the alternating strings, respectively. In this work, we present an algorithm for counting the number of subsequence embeddings using a run-length encoding of strings. We then describe two different ways of clustering the space of supersequences and prove that their cardinality depends only on the length of the received subsequence and its Hamming weight, but not its exact form. Then, we consider supersequences that contain a single embedding of a fixed subsequence, referred to as singletons, and provide a closed form expression for enumerating them using the same run-length encoding. We prove an analogous result for the minimization and maximization of the number of singletons, by the alternating and the uniform strings, respectively. Next, we prove the original minimal entropy conjecture for the special cases of single and double deletions using similar clustering techniques and the same run-length encoding, which allow us to characterize the distribution of the number of subsequence embeddings in the space of compatible supersequences to demonstrate the effect of an entropy decreasing operation. [less ▲]

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See detailA Security Analysis, and a Fix, of a Code-Corrupted Honeywords System
Genç, Ziya Alper UL; Lenzini, Gabriele UL; Ryan, Peter UL et al

in Proceedings of the 4th International Conference on Information Systems Security and Privacy (2018)

In 2013 Juels and Rivest introduced the Honeywords System, a password-based authentication system designed to detect when a password file has been stolen. A Honeywords System stores passwords together ... [more ▼]

In 2013 Juels and Rivest introduced the Honeywords System, a password-based authentication system designed to detect when a password file has been stolen. A Honeywords System stores passwords together with indistinguishable decoy words so when an intruder steals the file, retrieves the words, and tries to log-in, he does not know which one is the password. By guessing one from the decoy words, he may not be lucky and reveal the leak. Juels and Rivest left a problem open: how to make the system secure even when the intruder corrupted the login server’s code. In this paper we study and solve the problem. However, since “code corruption” is a powerful attack, we first define rigorously the threat and set a few assumptions under which the problem is still solvable, before showing meaningful attacks against the original Honeywords System. Then we elicit a fundamental security requirement, implementing which, we are able to restore the honeywords System’s security despite a corrupted login service. We verify the new protocol’s security formally, using ProVerif for this task. We also implement the protocol and test its performance. Finally, at the light of our findings, we discuss whether it is still worth using a fixed honeywords-based system against such a powerful threat, or whether it is better, in order to be resilient against code corruption attacks, to design afresh a completely different password-based authentication solution. [less ▲]

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See detailNo Random, No Ransom: A Key to Stop Cryptographic Ransomware
Genç, Ziya Alper UL; Lenzini, Gabriele UL; Ryan, Peter UL

in Giuffrida, Cristiano; Bardin, Sébastien; Blanc, Gregory (Eds.) Proceedings of the 15th International Conference on Detection of Intrusions and Malware, and Vulnerability Assessment (DIMVA 2018) (2018)

To be effective, ransomware has to implement strong encryption, and strong encryption in turn requires a good source of random numbers. Without access to true randomness, ransomware relies on the pseudo ... [more ▼]

To be effective, ransomware has to implement strong encryption, and strong encryption in turn requires a good source of random numbers. Without access to true randomness, ransomware relies on the pseudo random number generators that modern Operating Systems make available to applications. With this insight, we propose a strategy to mitigate ransomware attacks that considers pseudo random number generator functions as critical resources, controls accesses on their APIs and stops unauthorized applications that call them. Our strategy, tested against 524 active real-world ransomware samples, stops 94% of them, including WannaCry, Locky, CryptoLocker and CryptoWall. Remarkably, it also nullifies NotPetya, the latest offspring of the family which so far has eluded all defenses. [less ▲]

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See detailSecurity Analysis of Key Acquiring Strategies Used by Cryptographic Ransomware
Genç, Ziya Alper UL; Lenzini, Gabriele UL; Ryan, Peter UL

in Advances in Cybersecurity 2018 (2018)

To achieve its goals, ransomware needs to employ strong encryption, which in turn requires access to high-grade encryption keys. Over the evolution of ransomware, various techniques have been observed to ... [more ▼]

To achieve its goals, ransomware needs to employ strong encryption, which in turn requires access to high-grade encryption keys. Over the evolution of ransomware, various techniques have been observed to accomplish the latter. Understanding the advantages and disadvantages of each method is essential to develop robust defense strategies. In this paper we explain the techniques used by ransomware to derive encryption keys and analyze the security of each approach. We argue that recovery of data might be possible if the ransomware cannot access high entropy randomness sources. As an evidence to support our theoretical results, we provide a decryptor program for a previously undefeated ransomware. [less ▲]

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See detailSecurity in the Shell : An Optical Physical Unclonable Function made of Shells of Cholesteric Liquid Crystals
Lenzini, Gabriele UL; Samir, Ouchani; Roenne, Peter UL et al

in Proc. of the 9th IEEE Workshop on Information Forensics and Security (2017, October 02)

We describe the application in security of shells of Cholesteric Liquid Crystals (ChLCs). Such shells have a diameter in the microns range and can be gathered in hundreds in a surface area as small as a ... [more ▼]

We describe the application in security of shells of Cholesteric Liquid Crystals (ChLCs). Such shells have a diameter in the microns range and can be gathered in hundreds in a surface area as small as a nail’s head. Because of their structural properties, a bundle of them reflects light, creating colorful patterns that we argue to be unique and computationally hard to predict. We argue also that the bundle itself is unclonable. These are typical properties of Physically Unclonable Functions, a family to which shells of ChLCs belong too. Herein we discuss their physical and security properties and their potential use in object authentication. [less ▲]

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See detailDeniability in Quantum Cryptography
Atashpendar, Arash UL; Roenne, Peter UL; Ostrev, Dimiter UL et al

Poster (2017, June 14)

This poster describes ongoing work on deniability in quantum cryptography, an area of research that remains almost entirely unexplored in the quantum information processing literature. Deniability is a ... [more ▼]

This poster describes ongoing work on deniability in quantum cryptography, an area of research that remains almost entirely unexplored in the quantum information processing literature. Deniability is a well-known and fundamental concept in classical cryptography and it can be defined as the ability for the sender of a message to deny the contents of a message or the very act of having participated in an exchange, e.g. having sent the said message. We discuss deniability in the context of quantum key exchange and address a particular problem, first discovered by Donald Beaver, where he claims that all QKD protocols are undeniable. The claim is that while we do get a one-time pad (OTP) using QKD, it does not provide the property of key equivocation as it is expected in the Shannon sense for a OTP. Intuitively, this difficulty lies in the quantum channel alone and it has to do with the fact that in QKD, while we generate entropy by expanding an initially short pre-shared key into an arbitrary longer secret key, we do so by exchanging information over a quantum as well as a classical channel, which could potentially leave a binding transcript of Alice's decisions to the final secret key. This is in contrast with the implicit assumption that Eve knows nothing about how two given parties have established their shared OTP in the first place. We discuss the importance of deniability in cryptography and its wide range of applications, along with cryptographic primitives other than key exchange where deniability might be a desired property. Finally, we present a series of fundamental open questions in this area of research and discuss quantum cryptographic primitives that lend themselves to devising deniable protocols. [less ▲]

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See detailTrustworthy exams without trusted parties
Bella, Giampaolo; Giustolisi, Rosario; Lenzini, Gabriele UL et al

in Computer and Security (2017), 67

Historically, exam security has mainly focused on threats ascribed to candidate cheating. Such threats have been normally mitigated by invigilation and anti-plagiarism methods. However, as recent exam ... [more ▼]

Historically, exam security has mainly focused on threats ascribed to candidate cheating. Such threats have been normally mitigated by invigilation and anti-plagiarism methods. However, as recent exam scandals confirm, also invigilators and authorities may pose security threats. The introduction of computers into the different phases of an exam, such as candidate registration, brings new security issues that should be addressed with the care normally devoted to security protocols. This paper proposes a protocol that meets a wide set of security requirements and resists threats that may originate from candidates as well as from exam administrators. By relying on a combination of oblivious transfer and visual cryptography schemes, the protocol does not need to rely on any trusted third party. We analyse the protocol formally in ProVerif and prove that it verifies all the stated security requirements. [less ▲]

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See detailUsing Selene to Verify your Vote in JCJ
Iovino, Vincenzo UL; Rial Duran, Alfredo UL; Roenne, Peter UL et al

in Workshop on Advances in Secure Electronic Voting (VOTING'17) (2017, April 07)

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See detailThe Cipher, the Random and the Ransom: A Survey on Current and Future Ransomware
Genç, Ziya Alper UL; Lenzini, Gabriele UL; Ryan, Peter UL

in Advances in Cybersecurity 2017 (2017)

Although conceptually not new, ransomware recently regained attraction in the cybersecurity community: notorious attacks in fact have caused serious damage, proving their disruptive effect. This is likely ... [more ▼]

Although conceptually not new, ransomware recently regained attraction in the cybersecurity community: notorious attacks in fact have caused serious damage, proving their disruptive effect. This is likely just the beginning of a new era. According to a recent intelligence report by Cybersecurity Ventures, the total cost due to ransomware attacks is predicted to exceed $5 billion in 2017. How can this disruptive threat can be contained? Current anti-ransomware solutions are effective only against existing threats, and the worst is yet to come. Cyber criminals will design and deploy more sophisticated strategies, overcoming current defenses and, as it commonly happens in security, defenders and attackers will embrace a competition that will never end. In this arm race, anticipating how current ransomware will evolve may help at least being prepared for some future damage. In this paper, we describe existing techniques to mitigate ransomware and we discuss their limitations. Discussing how current ransomware could become even more disruptive and elusive is crucial to conceive more solid defense and systems that can mitigate zero-day ransomware, yielding higher security levels for information systems, including critical infrastructures such as intelligent transportation networks and health institutions. [less ▲]

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See detail(Universal) Unconditional Verifiability in E-Voting without Trusted Parties
Gallegos-Garcia, Gina; Iovino, Vincenzo UL; Roenne, Peter UL et al

E-print/Working paper (2016)

Detailed reference viewed: 56 (2 UL)
See detailReal-World Electronic Voting: Design, Analysis and Deployment
Hao, Feng; Ryan, Peter UL

Book published by Auerbach Publications (2016)

Detailed reference viewed: 64 (3 UL)
See detailFinancial Cryptography and Data Security - FC 2016 International Workshops, BITCOIN, VOTING, and WAHC
Clark, Jeremy; Sarah; Ryan, Peter UL et al

Book published by Springer (2016)

Detailed reference viewed: 69 (8 UL)
See detailThe New Codebreakers - Essays Dedicated to David Kahn on the Occasion of His 85th Birthday
Ryan, Peter UL; Naccache, David; Quisquater, Jean-Jacques

Book published by Springer (2016)

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See detailExpressing Receipt-Freeness and Coercion-Resistance in Logics of Strategic Ability: Preliminary Attempt
Tabatabaei, Masoud UL; Jamroga, Wojciech UL; Ryan, Peter UL

in The International Workshop on AI for Privacy and Security (PrAISe), 2016. (2016)

Voting is a mechanism of utmost importance to social processes. In this paper, we focus on the strategic aspect of information security in voting procedures. We argue that the notions of receipt-freeness ... [more ▼]

Voting is a mechanism of utmost importance to social processes. In this paper, we focus on the strategic aspect of information security in voting procedures. We argue that the notions of receipt-freeness and coercion resistance are underpinned by existence (or nonexistence) of a suitable strategy for some participants of the voting process. In order to back the argument formally, we provide logical ``transcriptions'' of the informal intuitions behind coercion-related properties that can be found in the existing literature. The transcriptions are formulated in the modal game logic ATL*, well known in the area of multi-agent systems. [less ▲]

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See detailCrypto Santa
Ryan, Peter UL

in The New Codebreakers - Essays Dedicated to David Kahn on the Occasion of His 85th Birthday (2016)

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See detailFormal Security Analysis of Traditional and Electronic Exams
Dreier, Jannik; Giustosi, Rosario; Kassem, Ali et al

in Communications in Computer and Information Science (2015), 554

Nowadays, students can be assessed not only by means of pencil-and-paper tests but also by electronic exams which they take in examination centers or even from home. Electronic exams are appealing as they ... [more ▼]

Nowadays, students can be assessed not only by means of pencil-and-paper tests but also by electronic exams which they take in examination centers or even from home. Electronic exams are appealing as they can reach larger audiences, but they are exposed to new threats that can potentially ruin the whole exam business. These threats are amplified by two issues: the lack of understanding of what security means for electronic exams (except the old concern about students cheating), and the absence of tools to verify whether an exam process is secure. This paper addresses both issues by introducing a formal description of several fundamental authentication and privacy properties, and by establishing the first theoretical framework for an automatic analysis of exam security. It uses the applied π-calculus as a framework and ProVerif as a tool. Three exam protocols are checked in depth: two Internet exam protocols of recent design, and the pencil-and-paper exam used by the University of Grenoble. The analysis highlights several weaknesses. Some invalidate authentication and privacy even when all parties are honest; others show that security depends on the honesty of parties, an often unjustified assumption in modern exams. [less ▲]

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See detailInformation Leakage due to Revealing Randomly Selected Bits
Atashpendar, Arash UL; Roscoe, Bill; Ryan, Peter UL

in Security Protocols XXIII: Lecture Notes in Computer Science, Volume 9379, 2015 (2015, November 25)

This note describes an information theory problem that arose from some analysis of quantum key distribution protocols. The problem seems very natural and is very easy to state but has not to our knowledge ... [more ▼]

This note describes an information theory problem that arose from some analysis of quantum key distribution protocols. The problem seems very natural and is very easy to state but has not to our knowledge been addressed before in the information theory literature: suppose that we have a random bit string y of length n and we reveal k bits at random positions, preserving the order but without revealing the positions, how much information about y is revealed? We show that while the cardinality of the set of compatible y strings depends only on n and k, the amount of leakage does depend on the exact revealed x string. We observe that the maximal leakage, measured as decrease in the Shannon entropy of the space of possible bit strings corresponds to the x string being all zeros or all ones and that the minimum leakage corresponds to the alternating x strings. We derive a formula for the maximum leakage (minimal entropy) in terms of n and k. We discuss the relevance of other measures of information, in particular min-entropy, in a cryptographic context. Finally, we describe a simulation tool to explore these results. [less ▲]

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See detailEnd-to-End Verifiability in Voting Systems, from Theory to Practice
Ryan, Peter UL; Schneider, Steve; Teague, Vanessa

in IEEE SECURITY & PRIVACY (2015), 13(3), 59-62

End-to-end verifiability represents a paradigm shift in electronic voting, providing a way to verify the integrity of the election by allowing voters to audit the information published by the system ... [more ▼]

End-to-end verifiability represents a paradigm shift in electronic voting, providing a way to verify the integrity of the election by allowing voters to audit the information published by the system, rather than trusting that the system has behaved correctly. Recent deployments of these systems in real elections demonstrate their practical applicability. [less ▲]

Detailed reference viewed: 154 (8 UL)