Understanding the Duplex and Its Security

At SAC 2011, Bertoni et al. introduced the keyed duplex construction as a tool to build permutation based authenticated encryption schemes. The construction was generalized to full-state absorption by Mennink et al. (ASIACRYPT 2015). Daemen et al. (ASIACRYPT 2017) generalized it further to cover much more use cases, and proved security of this general construction, and Dobraunig and Mennink (ASIACRYPT 2019) derived a leakage resilience security bound for this construction. Due to its generality, the full-state keyed duplex construction that we know today has plethora applications, but the flip side of the coin is that the general construction is hard to grasp and the corresponding security bounds are very complex. Consequently, the state-of-the-art results on the full-state keyed duplex construction are not used to the fullest. In this work, we revisit the history of the duplex construction, give a comprehensive discussion of its possibilities and limitations, and demonstrate how the two security bounds (of Daemen et al. and Dobraunig and Mennink) can be interpreted in particular applications of the duplex

Security analysis of NIST-LWC contest finalists

Dissertação de mestrado integrado em Informatics EngineeringTraditional cryptographic standards are designed with a desktop and server environment in mind, so, with the relatively recent proliferation of small, resource constrained devices in the Internet of Things, sensor networks, embedded systems, and more, there has been a call for lightweight cryptographic standards with security, performance and resource requirements tailored for the highly-constrained environments these devices find themselves in. In 2015 the National Institute of Standards and Technology began a Standardization Process in order to select one or more Lightweight Cryptographic algorithms. Out of the original 57 submissions ten finalists remain, with ASCON and Romulus being among the most scrutinized out of them. In this dissertation I will introduce some concepts required for easy understanding of the body of work, do an up-to-date revision on the current situation on the standardization process from a security and performance standpoint, a description of ASCON and Romulus, and new best known analysis, and a comparison of the two, with their advantages, drawbacks, and unique traits.Os padrões criptográficos tradicionais foram elaborados com um ambiente de computador e servidor em mente. Com a proliferação de dispositivos de pequenas dimensões tanto na Internet of Things, redes de sensores e sistemas embutidos, apareceu uma necessidade para se definir padrões para algoritmos de criptografia leve, com prioridades de segurança, performance e gasto de recursos equilibrados para os ambientes altamente limitados em que estes dispositivos operam. Em 2015 o National Institute of Standards and Technology lançou um processo de estandardização com o objectivo de escolher um ou mais algoritmos de criptografia leve. Das cinquenta e sete candidaturas originais sobram apenas dez finalistas, sendo ASCON e Romulus dois desses finalistas mais examinados. Nesta dissertação irei introduzir alguns conceitos necessários para uma fácil compreensão do corpo deste trabalho, assim como uma revisão atualizada da situação atual do processo de estandardização de um ponto de vista tanto de segurança como de performance, uma descrição do ASCON e do Romulus assim como as suas melhores análises recentes e uma comparação entre os dois, frisando as suas vantagens, desvantagens e aspectos únicos

Climate Change and the Structural Resilience of the Doha Metro

In recent years, the Doha Metro has been the spearhead of Qatar's effort to expand and upgrade its transportation infrastructure. In its current phase it will comprise three lines of an approximate overall length of 76 km and 37 stations. It is self-explanatory that such a significant infrastructure project should be a resilient one. The requirement for a 120 years design life for its permanent civil works structures implies that they should be resilient not only against the current environmental conditions, but also against future conditions due to the ongoing climate change. Resilient means that they will be able to serve their purpose under foreseen climatic changes during their design life. It is expected that climate change will increase the occurrence and intensity of weather events, especially in the Middle East and North Africa region. As per the AR5 assessment report of the Intergovernmental Panel on Climate Change "Climate change will have profound impacts on a broad spectrum of infrastructure systems..." transport being one of them. Furthermore, since transportation is interconnected with the economic and social welfare of an area, it is evident that the metro is a critical infrastructure system of Doha. In this paper, the climate change related main hazards on the Doha Metro permanent assets are presented along with the mitigation measures that have been adopted through provisions in the structural design and the materials used. Furthermore, suggestions for future contingency measures are made

Revisiting Shared Data Protection Against Key Exposure

This paper puts a new light on secure data storage inside distributed systems. Specifically, it revisits computational secret sharing in a situation where the encryption key is exposed to an attacker. It comes with several contributions: First, it defines a security model for encryption schemes, where we ask for additional resilience against exposure of the encryption key. Precisely we ask for (1) indistinguishability of plaintexts under full ciphertext knowledge, (2) indistinguishability for an adversary who learns: the encryption key, plus all but one share of the ciphertext. (2) relaxes the "all-or-nothing" property to a more realistic setting, where the ciphertext is transformed into a number of shares, such that the adversary can't access one of them. (1) asks that, unless the user's key is disclosed, noone else than the user can retrieve information about the plaintext. Second, it introduces a new computationally secure encryption-then-sharing scheme, that protects the data in the previously defined attacker model. It consists in data encryption followed by a linear transformation of the ciphertext, then its fragmentation into shares, along with secret sharing of the randomness used for encryption. The computational overhead in addition to data encryption is reduced by half with respect to state of the art. Third, it provides for the first time cryptographic proofs in this context of key exposure. It emphasizes that the security of our scheme relies only on a simple cryptanalysis resilience assumption for blockciphers in public key mode: indistinguishability from random, of the sequence of diferentials of a random value. Fourth, it provides an alternative scheme relying on the more theoretical random permutation model. It consists in encrypting with sponge functions in duplex mode then, as before, secret-sharing the randomness

Leakage and Tamper Resilient Permutation-Based Cryptography

Implementation attacks such as power analysis and fault attacks have shown that, if potential attackers have physical access to a cryptographic device, achieving practical security requires more considerations apart from just cryptanalytic security. In recent years, and with the advent of micro-architectural or hardware-oriented attacks, it became more and more clear that similar attack vectors can also be exploited on larger computing platforms and without the requirement of physical proximity of an attacker. While newly discovered attacks typically come with implementation recommendations that help counteract a specific attack vector, the process of constantly patching cryptographic code is quite time consuming in some cases, and simply not possible in other cases. What adds up to the problem is that the popular approach of leakage resilient cryptography only provably solves part of the problem: it discards the threat of faults. Therefore, we put forward the usage of leakage and tamper resilient cryptographic algorithms, as they can offer built-in protection against various types of physical and hardware oriented attacks, likely including attack vectors that will only be discovered in the future. In detail, we present the - to the best of our knowledge - first framework for proving the security of permutation-based symmetric cryptographic constructions in the leakage and tamper resilient setting. As a proof of concept, we apply the framework to a sponge-based stream encryption scheme called asakey and provide a practical analysis of its resistance against side channel and fault attacks

Arctic Resilience: Adaptive Networks of Self-Sufficiency

As the impacts of climate change reverberate across the globe, there is an increasing focus on communities already grappling with high environmental stress, limited resources, isolation, and economic challenges. Among these communities, the Arctic region stands out not for its population size, but for the threat posed to their traditional ways of life by the melting polar icecap, rising seas, changing ecology, and shifting migration patterns of vital wildlife. Many communities are living on shorelines being lost to the sea, having been moved there decades earlier by government and oil corporation dictates. Now facing impending relocation again, these communities have a unique opportunity to reimagine settlement patterns, community design, and regain autonomy from government dependence. At present, many of these communities are experiencing a significant amount of resource wastage. Factors such as inefficient use of energy, water, and materials, combined with inadequate waste management systems, contribute to unsustainable living practices. This not only puts a strain on the already limited resources available in these Arctic coastal communities but also exacerbates their vulnerability to climate change impacts. The existing strategies are quite basic and meet the fundamental requirements, but they lack resilience in the face of drastic environmental changes and do not maximize resource utilization. In this context, this thesis focuses on rearranging resources to design a closed-loop system for living in extreme cold environments and marginalized populations and how those living in a landscape of scarcity can make better use of the resources around them to achieve greater self-sufficiency through adopting a circular economy model that integrates shelter and land with food production, energy, water, and waste

Kirby: A Robust Permutation-Based PRF Construction

We present a construction, called Kirby, for building a variable-input-length pseudorandom function (VIL-PRF) from a $b$-bit permutation. For this construction we prove a tight bound of $b/2$ bits of security on the PRF distinguishing advantage in the random permutation model and in the multi-user setting. Similar to full-state keyed sponge/duplex, it supports full-state absorbing and additionally supports full-state squeezing, where the latter can at most squeeze $b-c$ bits per permutation call for a security level of $c$ bits. This advantage is especially relevant on constrained platforms when using a permutation with small width $b$. For instance, for $b=256$ at equal security strength the squeezing rate of Kirby is twice that of keyed sponge/duplex. We define a simple mode on top of Kirby that turns it into a deck function with parallel expansion. This deck function is suited for lightweight applications in the sense that it has a low memory footprint. Moreover, for short inputs it can be used for low-latency stream encryption: the time between the availability of the input and the keystream is only a single permutation call. Another feature that sets Kirby apart from other constructions is that leakage of an intermediate state does not allow recovering the key or $\textit{earlier states}$