PRISEC: Comparison of Symmetric Key Algorithms for IoT Devices

With the growing number of heterogeneous resource-constrained devices connected to the Internet, it becomes increasingly challenging to secure the privacy and protection of data. Strong but efficient cryptography solutions must be employed to deal with this problem, along with methods to standardize secure communications between these devices. The PRISEC module of the UbiPri middleware has this goal. In this work, we present the performance of the AES (Advanced Encryption Standard), RC6 (Rivest Cipher 6), Twofish, SPECK128, LEA, and ChaCha20-Poly1305 algorithms in Internet of Things (IoT) devices, measuring their execution times, throughput, and power consumption, with the main goal of determining which symmetric key ciphers are best to be applied in PRISEC. We verify that ChaCha20-Poly1305 is a very good option for resource constrained devices, along with the lightweight block ciphers SPECK128 and LEA.info:eu-repo/semantics/publishedVersio

Popularity prediction of instagram posts

Predicting the popularity of posts on social networks has taken on significant importance in recent years, and several social media management tools now offer solutions to improve and optimize the quality of published content and to enhance the attractiveness of companies and organizations. Scientific research has recently moved in this direction, with the aim of exploiting advanced techniques such as machine learning, deep learning, natural language processing, etc., to support such tools. In light of the above, in this work we aim to address the challenge of predicting the popularity of a future post on Instagram, by defining the problem as a classification task and by proposing an original approach based on Gradient Boosting and feature engineering, which led us to promising experimental results. The proposed approach exploits big data technologies for scalability and efficiency, and it is general enough to be applied to other social media as well

An Enhanced Dataflow Analysis to Automatically Tailor Side Channel Attack Countermeasures to Software Block Ciphers

Protecting software implementations of block ciphers from side channel attacks is a significant concern to realize secure embedded computation platforms. The relevance of the issue calls for the automation of the side channel vulnerability assessment of a block cipher implementation, and the automated application of provably secure defenses. The most recent methodology in the field is an application of a specialized data-flow analysis, performed by means of the LLVM compiler framework, detecting in the AES cipher the portions of the code amenable to key extraction via side channel analysis. The contribution of this work is an enhancement to the existing data-flow analysis which extending it to tackle any block cipher implemented in software. In particular, the extended strategy takes fully into account the data dependencies present in the key schedule of a block cipher, regardless of its complexity, to obtain consistently sound results. This paper details the analysis strategy and presents new results on the tailored application of power and electro-magnetic emission analysis countermeasures, evaluating the performances on both the ARM Cortex-M and the MIPS ISA. The experimental evaluation reports a case study on two block ciphers: the first designed to achieve a high security margin at a non-negligible computational cost, and a lightweight one. The results show that, when side-channel-protected implementations are considered, the high-security block cipher is indeed more efficient than the lightweight one

Secure and Scalable Multi-User Searchable Encryption

By allowing a large number of users to behave as readers or writers, Multi-User Searchable Encryption (MUSE) raises new security and performance challenges beyond the typical requirements of Symmetric Searchable Encryption (SSE). In this paper we identify two core mandatory requirements of MUSE protocols being privacy in face of users colluding with the CSP and low complexity for the users, pointing that no existing MUSE protocol satisfies these two requirements at the same time. We then come up with the first MUSE protocol that satisfies both of them. The design of the protocol also includes new constructions for a secure variant of Bloom Filters (BFs) and multi-query Oblivious Transfer (OT)

Randomness Generation for Secure Hardware Masking - Unrolled Trivium to the Rescue

Masking is a prominent strategy to protect cryptographic implementations against side-channel analysis. Its popularity arises from the exponential security gains that can be achieved for (approximately) quadratic resource utilization. Many variants of the countermeasure tailored for different optimization goals have been proposed over the past decades. The common denominator among all of them is the implicit demand for robust and high entropy randomness. Simply assuming that uniformly distributed random bits are available, without taking the cost of their generation into account, leads to a poor understanding of the efficiency and performance of secure implementations. This is especially relevant in case of hardware masking schemes which are known to consume large amounts of random bits per cycle due to parallelism. Currently, there seems to be no consensus on how to most efficiently derive many pseudo-random bits per clock cycle from an initial seed and with properties suitable for masked hardware implementations. In this work, we evaluate a number of building blocks for this purpose and find that hardware-oriented stream ciphers like Trivium and its reduced-security variant Bivium B outperform all competitors when implemented in an unrolled fashion. Unrolled implementations of these primitives enable the flexible generation of many bits per cycle while maintaining high performance, which is crucial for satisfying the large randomness demands of state-of-the-art masking schemes. According to our analysis, only Linear Feedback Shift Registers (LFSRs), when also unrolled, are capable of producing long non-repetitive sequences of random-looking bits at a high rate per cycle even more efficiently than Trivium and Bivium B. Yet, these instances do not provide black-box security as they generate only linear outputs. We experimentally demonstrate that using multiple output bits from an LFSR in the same masked implementation can violate probing security and even lead to harmful randomness cancellations. Circumventing these problems, and enabling an independent analysis of randomness generation and masking scheme, requires the use of cryptographically stronger primitives like stream ciphers. As a result of our studies, we provide an evidence-based estimate for the cost of securely generating n fresh random bits per cycle. Depending on the desired level of black-box security and operating frequency, this cost can be as low as 20n to 30n ASIC gate equivalents (GE) or 3n to 4n FPGA look-up tables (LUTs), where n is the number of random bits required. Our results demonstrate that the cost per bit is (sometimes significantly) lower than estimated in previous works, incentivizing parallelism whenever exploitable and potentially moving low randomness usage in hardware masking research from a primary to secondary design goal

On Selection of Samples in Algebraic Attacks and a New Technique to Find Hidden Low Degree Equations

The best way of selecting samples in algebraic attacks against block ciphers is not well explored and understood. We introduce a simple strategy for selecting the plaintexts and demonstrate its strength by breaking reduced-round KATAN, LBLOCK and SIMON. For each case, we present a practical attack on reduced round version which outperforms previous attempts of algebraic cryptanalysis whose complexities were close to exhaustive search. The attack is based on the selection of samples using cube attack and ELIMLIN which was presented at FSE'12, and a new technique called proning. In the case of LBLOCK, we break 10 out of 32 rounds. In KATAN, we break 78 out of 254 rounds. Unlike previous attempts which break smaller number of rounds, we do not guess any bit of the key and we only use structural properties of the cipher to be able to break a higher number of rounds with much lower complexity. We show that cube attacks owe their success to the same properties and therefore, can be used as a heuristic for selecting the samples in an algebraic attack. The performance of ELIMLIN is further enhanced by the new proning technique, which allows to discover linear equations that are not found by ELIMLIN

Updatable Tokenization: Formal Definitions and Provably Secure Constructions

Tokenization is the process of consistently replacing sensitive elements, such as credit cards numbers, with non-sensitive surrogate values. As tokenization is mandated for any organization storing credit card data, many practical solutions have been introduced and are in commercial operation today. However, all existing solutions are static yet, i.e., they do not allow for efficient updates of the cryptographic keys while maintaining the consistency of the tokens. This lack of updatability is a burden for most practical deployments, as cryptographic keys must also be re-keyed periodically for ensuring continued security. This paper introduces a model for updatable tokenization with key evolution, in which a key exposure does not disclose relations among tokenized data in the past, and where the updates to the tokenized data set can be made by an untrusted entity and preserve the consistency of the data. We formally define the desired security properties guaranteeing unlinkability of tokens among different time epochs and one-wayness of the tokenization process. Moreover, we construct two highly efficient updatable tokenization schemes and prove them to achieve our security notions

Automated Verification of Exam, Cash, aa Reputation, and Routing Protocols

Security is a crucial requirement in the applications based on information and communication technology, especially when an open network such as the Internet is used.To ensure security in such applications cryptographic protocols have been used.However, the design of security protocols is notoriously difficult and error-prone.Several flaws have been found on protocols that are claimed secure.Hence, cryptographic protocols must be verified before they are used.One approach to verify cryptographic protocols is the use of formal methods, which have achieved many results in recent years.Formal methods concern on analysis of protocol specifications modeled using, e.g., dedicated logics, or process algebras.Formal methods can find flaws or prove that a protocol is secure under ``perfect cryptographic assumption" with respect to given security properties. However, they abstract away from implementation errors and side-channel attacks.In order to detect such errors and attacks runtime verification can be used to analyze systems or protocols executions.Moreover, runtime verification can help in the cases where formal procedures have exponential time or suffer from termination problems.In this thesis we contribute to cryptographic protocols verification with an emphasis on formal verification and automation.Firstly, we study exam protocols. We propose formal definitions for several authentication and privacy propertiesin the Applied Pi-Calculus. We also provide an abstract definitions of verifiability properties.We analyze all these properties automatically using ProVerif on multiple case studies, and identify several flaws.Moreover, we propose several monitors to check exam requirements at runtime. These monitors are validated by analyzing a real exam executions using MARQ Java based tool.Secondly, we propose a formal framework to verify the security properties of non-transferable electronic cash protocols.We define client privacy and forgery related properties.Again, we illustrate our model by analyzing three case studies using ProVerif, and confirm several known attacks.Thirdly, we propose formal definitions of authentication, privacy, and verifiability properties of electronic reputation protocols. We discuss the proposed definitions, with the help of ProVerif, on a simple reputation protocol.Finally, we obtain a reduction result to verify route validity of ad-hoc routing protocols in presence of multiple independent attackers that do not share their knowledge.La sécurité est une exigence cruciale dans les applications basées sur l'information et la technologie de communication, surtout quand un réseau ouvert tel que l'Internet est utilisé. Pour assurer la sécurité dans ces applications des protocoles cryptographiques ont été développé. Cependant, la conception de protocoles de sécurité est notoirement difficile et source d'erreurs. Plusieurs failles ont été trouvées sur des protocoles qui se sont prétendus sécurisés. Par conséquent, les protocoles cryptographiques doivent être vérifiés avant d'être utilisés. Une approche pour vérifier les protocoles cryptographiques est l'utilisation des méthodes formelles, qui ont obtenu de nombreux résultats au cours des dernières années.Méthodes formelles portent sur l'analyse des spécifications des protocoles modélisées en utilisant, par exemple, les logiques dédiés, ou algèbres de processus. Les méthodes formelles peuvent trouver des failles ou permettent de prouver qu'un protocole est sécurisé sous certaines hypothèses par rapport aux propriétés de sécurité données. Toutefois, elles abstraient des erreurs de mise en ouvre et les attaques side-channel.Afin de détecter ces erreurs et la vérification des attaques d'exécution peut être utilisée pour analyser les systèmes ou protocoles exécutions. En outre, la vérification de l'exécution peut aider dans les cas où les procédures formelles mettent un temps exponentielle ou souffrent de problèmes de terminaison. Dans cette thèse, nous contribuons à la vérification des protocoles cryptographiques avec un accent sur la vérification formelle et l'automatisation. Tout d'abord, nous étudions les protocoles d'examen. Nous proposons des définitions formelles pour plusieurs propriétés d'authentification et de confidentialité dans le Pi-calcul Appliqué.Nous fournissons également une des définitions abstraites de propriétés de vérifiabilité. Nous analysons toutes ces propriétés en utilisant automatiquement ProVerif sur plusieurs études de cas, et avons identifié plusieurs failles. En outre, nous proposons plusieurs moniteurs de vérifier les exigences d'examen à l'exécution. Ces moniteurs sont validés par l'analyse d'un exécutions d'examen réel en utilisant l'outil MARQ Java.Deuxièmement, nous proposons un cadre formel pour vérifier les propriétés de sécurité de protocoles de monnaie électronique non transférable. Nous définissons la notion de vie privée du client et les propriétés de la falsification. Encore une fois, nous illustrons notre modèle en analysant trois études de cas à l'aide ProVerif, et confirmons plusieurs attaques connues.Troisièmement, nous proposons des définitions formelles de l'authentification, la confidentialité et les propriétés de vérifiabilité de protocoles de réputation électroniques. Nous discutons les définitions proposées, avec l'aide de ProVerif, sur un protocole de réputation simple. Enfin, nous obtenons un résultat sur la réduction de la vérification de la validité d'une route dans les protocoles de routage ad-hoc, en présence de plusieurs attaquants indépendants qui ne partagent pas leurs connaissances