Ruhr-Universität Bochum (RUB): Open Journal Systems
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Francesc Fontanella: Amor, firmesa i porfia. Lo Desengany. A cura de Pep Valsalobre i Albert Rossich. Barcelona: Barcino, 2022
Get PDFThe Way to the Way: Classical Daoist Apophatic Meditation as Effortless Practice
No full textThe present article explores Daoist effortless meditation with particular attention to its association with the inner cultivation lineages of classical Daoism (ca. 350–ca. 90 BCE). In addition to discussing the technical specifics of the practice, including its intimate connection to wúwéi 無為 (lit., ‘without acting/doing’; non-action/effortlessness), consideration is given to related contemplative states and traits. The article also encourages readers and researchers to examine contemplative practice in general and meditation in particular beyond mere technique. Here one engages the associated aesthetics, material culture, place, spatiality, and so forth. The piece concludes with some reflections from a lived/living Daoist perspective
BEANIE – A 32-bit Cipher for Cryptographic Mitigations Against Software Attacks
No full textIn modern CPU architectures, various security features to mitigate software attacks can be found. Examples of such features are logical isolation, memory tagging or shadow stacks. Basing such features on cryptographic isolation instead of logical checks can have many advantages such as lower memory overhead and more robustness against misconfiguration or low-cost physical attacks. The disadvantage of such an approach is however that the cipher that has to be introduced has a severe impact on the system performance, either in terms of additional cycles or a decrease of the maximum achievable frequency. Finally, as of today, there is no suitable low-latency cipher design available for encrypting 32-bit words as is common in microcontrollers. In this paper, we propose a 32-bit tweakable block cipher tailored to memory encryption for microcontroller units. We optimize this cipher for low latency, which we achieve by a careful selection of components for the round function and leveraging an attack scenario similar to the one used to analyze the cipher SCARF. To mitigate some attack vectors introduced by this attack scenario, we deploy a complex tweak-key schedule. Due to the shortage of suitable 32-bit designs, we compare our design to various low-latency ciphers with different block sizes. Our hardware implementation shows competitive latency numbers
How to Implement Authenticated Encryption on XTS-Enabled Devices
No full textXTS is a block cipher mode for storage encryption. IEEE and NIST have standardized it, and it is widely deployed in real-world applications, including FileVault2, Bitlocker, and dm-crypt. However, it is well-known that XTS provides limited confidentiality and no integrity. XTS prevents simple attacks, e.g., information extraction from a stolen device. However, applications of XTS are expanding, such as cloud storage and CPU memory, where this issue implies a significant security threat. To address this issue, we propose iXTS, a family of black-box conversion methods of XTS into an authenticated encryption (AE). To make our proposal usable in practice, we need to assume that the only controllable part of the XTS engine is the plaintext input, because XTS engine’s ciphertext output is typically directly connected to the storage device and we assume the adversary is able to access the device directly, in addition to the black-box access to the engine. It is also desirable that the conversion could be done without the knowledge of the internal XTS key and without touching it. These constraints pose non-trivial technical challenges, and iXTS is the first effective solution meeting these constraints. We prove that each member of iXTS achieves n/2-bit security as a randomized AE using an n-bit block cipher. This security level is equivalent to popular AE modes such as GCM. iXTS is efficient as it requires no additional cryptographic computation beyond the original XTS. Plaintexts are expanded by a small amount, which is necessary for achieving AE. Our benchmarks on Intel platforms with AES-NI demonstrated that iXTS incurs only minor computation overhead from the underlying XTS
Improved Cryptanalysis of GIFT-64
No full textIn this paper, we propose new differential attacks against the block cipher GIFT-64. First we demonstrate how the parallel matching algorithm proposed by Naya-Plasencia at CRYPTO’11 as an advanced list-merging algorithm can be leveraged to enhance differential attacks, overcoming a previously assumed bottleneck. By reducing the complexity of the pairs generation process whenever a non-linear filter is available, this approach enabled us to mount a new differential attack against 25-round GIFT-64 in the related-key setting.Then we use the differential Meet-in-the-Middle cryptanalysis technique introduced by Boura et al. at CRYPTO’23 to improve the differential attacks recently proposed by Chang et al. at CT-RSA’25, leading to the best known attacks against GIFT-64 in the single-key setting, both in term of number of rounds and of complexity
“All I did was cry”: Women’s Experiences of Harm and Violence in Transit
No full textThis article explores how migrant women experience harm, resilience, and agency while in transit through the Americas. It focuses on the ways sexual and gender-based violence (SGBV) shapes mobility, everyday life, and perception, drawing on women’s own words to trace how harm accumulates both through direct acts of violence and through the constant threat of it. The article situates these experiences within the continuum of violence framework, understanding violence as a process that crosses borders, stages, and forms rather than as isolated incidents. Based on qualitative fieldwork conducted in Honduras in 2024, it centres on the testimony of one Venezuelan woman travelling with her three daughters whose narrative reveals the entanglement of fear, care, exhaustion, and determination that defines life on the move. Her story, like those of many others, challenges one-dimensional portrayals of migrant women as passive victims and instead foregrounds strategies of endurance, mutual support, and self protection. The analysis shows that even in extreme vulnerability, women navigate danger through acts of choice and solidarity that complicate conventional binaries of victimhood and agency. In highlighting these dynamics, the article calls for humanitarian and academic approaches that recognise women’s voices not only as evidence of suffering but as sources of knowledge and power for understanding the lived realities of migration and violence
A New Stand-Alone MAC Construct Called SMAC
Get PDFIn this paper, we present a new efficient stand-alone MAC construct named SMAC, based on processing using the Finite State Machine (FSM) part of the stream cipher family SNOW, which in turn uses the AES round function. It offers a combination of very high speed in software and hardware with a truncatable tag. Three concrete base versions of SMAC are proposed, each offering a different security level. SMAC can also be directly integrated with an external ciphering engine in an AEAD mode. Every design decision is thoroughly justified and supported by the results of our cryptanalysis and simulations. Additionally, we introduce an aggregated mode version, SMAC-1xn, in which software performance reaches up to 925 Gbps (around 0.038 cycles per byte) for long messages in a single thread. To the best of our knowledge, SMAC achieves a record-breaking software performance compared to all known MAC engines
On the Security of Split-and-Lookup-Based ZK-Friendly Primitives
Get PDFArithmetization-Oriented hash functions are optimized for their verification to be efficiently implemented within various proof systems, but they are often too slow when evaluated on a regular machine. To solve this problem for some specific protocols, some recent proposals introduced a new type of operations: the Split- And-Lookup. The idea in this case is to “split” prime field elements into smaller integers, e.g. by simply considering their binary representations, and then applying a permutation on each such integer before rebuilding a field element from them. Such operations are fast to evaluate, and of a very high degree in the field, which hopefully implies a high resistance against algebraic attacks.In this paper, we investigate the security offered by such components using two distinct approaches. First, we provide a detailed analysis of the cryptographic properties of the Split-And-Lookup construction. In particular, we present technique to efficiently compute its Fourier coefficients and linear approximation probabilities, and use them to show linear approximations of the S-boxes of Skyscraper, Monolith, Tip5, and Reinforced Concrete with surprisingly high probabilities. We also present our own S-boxes that could be used as a drop-in replacement for those of Monolith and Tip5, and would provide enhanced security and performances in some contexts. Finally, we turn our attention to the primitives themselves, and present a freestart partial preimage attack on a version of Tip5 reduced to four out of five rounds, where the attacker is allowed to control only one word in the initialization vector. This can be turned into a collision attack against a four-round version of Tip5 with a capacity reduced to 320 bits out of 384, though it should still provide the same security level as the original hash function. Despite the high degree of the Split-And- Lookup construction, we use an algebraic attack that essentially goes “around” these components.While these results do not directly threaten the security of full-round primitives, they further the understanding of the cryptographic properties of these new operations, and of the actual impact they have on the security against various attacks
Protection of Oscillator-Based PUFs against Side Channel Analyses by Random Interruption
Get PDFOscillation-based physical unclonable functions (PUFs) are known to be sensitive to power trace side channel analyses (SCAs). Although previous work investigated on countermeasures, these required significant additional amount of hardware or were just able to obscure sign information of a frequency comparison, while the magnitude information remains available to the attacker. As recent innovation on oscillation-based PUFs also require the magnitude-information beside the sign, e.g., to increase the reliability, the need arises to protect both. We present a new protection approach to hide both sign and magnitude information of oscillation-based PUF from an attacker. By introducing random interruptions in the oscillation, the power spectrum is blurred while the quality of the PUF is maintained. In addition to concept simulations and the discussion of different implementations, we use the example of a loop-PUF to show that the presented countermeasure can withstand several attack scenarios
All You Need is XOR-Convolution: A Generalized Higher-Order Side-Channel Attack with Application to XEX/XE-based Encryptions
Get PDFThe XEX/XE scheme has been widely used to realize authenticated encryptions (AEs), message authentication codes (MACs), and storage encryptions, such as OCB, PMAC, and XTS. Although these schemes have been extensively deployed in the real world, limited studies have evaluated side-channel attacks (SCAs) on them. In this study, we propose an efficient SCA that can be applied to the XEX/XE scheme. Despite the fact that the offset generated in these modes is guaranteed to have no full offset collision with an overwhelming probability, we analyze their offset-generating routines to exploit the partial offset collisions. Then, we propose a new profiled SCA named XOR-convoluting collision analysis (XCCA), which estimates the sum of keys from two leakages by XOR-convoluting probability distributions that model the leakages. The proposed collision SCA effectively erases the effect of random offsets by using XOR-convolution, whereas conventional collision SCAs are ineffective in this scenario. We validated the proposed SCA through simulations and experimental attacks using real traces. The results confirmed that the proposed SCA reduces the number of traces by up to 90% to achieve a success rate identical to that of a state-of-the-art SCA on OCB in TCHES 2022. Furthermore, we show that the proposed SCA distinguisher (XCCA distinguisher) is a generalization of higher-order SCAs, including non-collision SCAs on masked implementations. The profiled higher-order SCAs on masked implementations can be written in the form of an XCCA distinguisher using XOR-convolution with the new concept of leaking and target selection functions. The generalized representation clarifies how and why a higher-order SCA has better or worse performance from the theoretical viewpoint of noise amplification, which is also demonstrated through experiments and a spectrum analysis based on Walsh–Hadamard transform (WHT). Our analysis reveals that the random offsets of XEX/XE would work as masking from an SCA perspective, and XEX/XE-based encryption would have an inherent first-order SCA resilience under certain conditions