Block Ciphers that are Easier to Mask: How Far Can we Go?

The design and analysis of lightweight block ciphers has been a very active research area over the last couple of years, with many innovative proposals trying to optimize different performance figures. However, since these block ciphers are dedicated to low-cost embedded devices, their implementation is also a typical target for side-channel adversaries. As preventing such attacks with countermeasures usually implies significant performance overheads, a natural open problem is to propose new algorithms for which physical security is considered as an optimization criteria, hence allowing better performances again. We tackle this problem by studying how much we can tweak standard block ciphers such as the AES Rijndael in order to allow efficient masking (that is one of the most frequently considered solutions to improve security against side-channel attacks). For this purpose, we first investigate alternative S-boxes and round structures. We show that both approaches can be used separately in order to limit the total number of non-linear operations in the block cipher, hence allowing more efficient masking. We then combine these ideas into a concrete instance of block cipher called Zorro. We further provide a detailed security analysis of this new cipher taking its design specificities into account, leading us to exploit innovative techniques borrowed from hash function cryptanalysis (that are sometimes of independent interest). Eventually, we conclude the paper by evaluating the efficiency of masked Zorro implementations in an 8-bit microcontroller, and exhibit their interesting performance figures

The Fool-Knave Relation in Picaresque Satire

Paper by Ronald Paulso

Key-dependent side-channel cube attack on CRAFT

CRAFT is a tweakable block cipher introduced in 2019 that aims to provide strong protection against differential fault analysis. In this paper, we show that CRAFT is vulnerable to side-channel cube attacks. We apply side-channel cube attacks to CRAFT with the Hamming weight leakage assumption. We found that the first half of the secret key can be recovered from the Hamming weight leakage after the first round. Next, using the recovered key bits, we continue our attack to recover the second half of the secret key. We show that the set of equations that are solvable varies depending on the value of the key bits. Our result shows that 99.90% of the key space can be fully recovered within a practical time

Picaresque and romance in Golden Age Spain and postcolonial Britain : a comparative study

Multiculturalism is not a new phenomenon in European history. Neither are its literary and artistic manifestations. This thesis compares and contrasts two distant but similar multicultural contexts: Golden Age Spain and postmodern Britain. Picaresque and romance are chosen to illustrate how authors question religious oppression, cultural intolerance and thought control within multicultural contexts. Cervantes and Rushdie give voice to marginalised minorities and deconstruct the grand-narratives of religion; Aleman, Kureishi, Dhondy and the author of Estebanillo Gonzalez all depict life at the margins.The establishment of a counter-canonical critique of literary tradition in Golden Age Spain, and the emergence and development of genres such as the picaresque, would not have been possible without Spain's multicultural heritage and the presence of Spanish marginal and dissident voices. Gradually these voices from the periphery vanished as Spanish minorities were absorbed by the centre. Likewise, the power to confront of a marginal genre, such as the picaresque, disappeared. From the Spanish case we can draw a parallel in contemporary Britain, where representations of the margins are becoming absorbed into the mainstream. Postmodern Britain recalls the Spanish case not only in terms of the emergence of minority voices which are being absorbed by the centre, but also in terms of the choice of genres to express hybridity, difference and cross cultural and religious encounters. However, there is a difference between sixteenth and seventeenth century Spain and postmodern Britain; ethnicity has become desirable

Wayward fictions: A study of the dynamic picaresque novel

The picaresque has been considered a narrow and historically closed genre, limited to a few examples, as well as a wide and flexible genre inclusive of any number of narratives. As an alternative, I propose that it should be seen as a dynamic form, conserving certain historic characteristics, but also adapting to newly current, mostly social, concerns by reconfiguring form and content. Through its double structure it incorporates inconsistencies and controversies, remaining culturally relevant. In the following chapters I have redefined the picaresque elements of two well-known British picaresque novels, added another picaresque novel to the canon, and qualified two others, taking siglo-de-oro Spain for my point of departure. In my final chapter I argue for the continuing relevance of the genre by showing how it reappears in postmodern Germany through Thomas Brussig\u27s Heroes Like Us; Moll Flanders by Daniel Defoe, John le Brun by Richard Cross, and Roderick Random by Tobias Smollett are picaresque on the dynamic view, their picaresque characteristics being modified to express period thought. These works conserve the historic ambivalent form and the duality of content. While all three novels attempt to resolve status inconsistency, their solutions are variously flawed. In each of them one aspect gives especially interesting insight into cultural developments: in Moll Flanders the relation of signified to signifier, in John le Brun the development towards a class society, and in Roderick Random a change in narrative concepts, all illustrate epistemic shifts. Meanwhile, not all picaresque novels are so rewarding to the critic because some, like the anonymous Frank Hammond, employ picaresque features without adapting them to contemporary conventions and circumstances. Other novels such as Edward Kimber\u27s Joe Thompson follow the picaresque format only in part, either as generic hybrids or lacking cultural import consistent with the picaresque novel; The picaresque novel reconfigures various social and cultural discourses with traditional as well as emergent elements. As a sub-genre, the picaresque shares elements with the novel, and it is precisely in the adaptation of generic features that it may be understood as a hitherto undervalued stepping stone in the development of the modern novel

CRAFT: Lightweight Tweakable Block Cipher with Efficient Protection Against DFA Attacks

Traditionally, countermeasures against physical attacks are integrated into the implementation of cryptographic primitives after the algorithms have been designed for achieving a certain level of cryptanalytic security. This picture has been changed by the introduction of PICARO, ZORRO, and FIDES, where efficient protection against Side-Channel Analysis (SCA) attacks has been considered in their design. In this work we present the tweakable block cipher CRAFT: the efficient protection of its implementations against Differential Fault Analysis (DFA) attacks has been one of the main design criteria, while we provide strong bounds for its security in the related-tweak model. Considering the area footprint of round-based hardware implementations, CRAFT outperforms the other lightweight ciphers with the same state and key size. This holds not only for unprotected implementations but also when fault-detection facilities, side-channel protection, and their combination are integrated into the implementation. In addition to supporting a 64-bit tweak, CRAFT has the additional property that the circuit realizing the encryption can support the decryption functionality as well with very little area overhead

DFA on LS-Designs with a Practical Implementation on SCREAM (extended version)

LS-Designs are a family of SPN-based block ciphers whose linear layer is based on the so-called interleaved construction. They will be dedicated to low-end devices with high performance and low-resource constraints, objects which need to be resistant to physical attacks. In this paper we describe a complete Differential Fault Analysis against LS-Designs and also on other families of SPN-based block ciphers. First we explain how fault attacks can be used against their implementations depending on fault models. Then, we validate the DFA in a practical example on a hardware implementation of SCREAM running on an FPGA. The faults have been injected using electromagnetic pulses during the execution of SCREAM and the faulty ciphertexts have been used to recover the key’s bits. Finally, we discuss some countermeasures that could be used to thwart such attacks