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follow the framework used by Beaulieu et al. from the United States National Security Agency
(NSA) to design SIMON and SPECK. A cipher in this family with K-bit key and N-bit block is
called SIMECKN=K.We show that the security of this block cipher against linear cryptanalysis
is not as good as its predecessors SIMON. More precisely, while the best known linear attack
for SIMON32/64, using algorithm 1 of Matsui, covers 13 rounds we present a linear attack in
this senario which covers 14 rounds of SIMECK32/64. Similarly, using algorithm 1 of Matsui,
we present attacks on 19 and 22 rounds of SIMECK48/96 and SIMECK64/128 respectively,
compare them with known attacks on 16 and 19 rounds SIMON48/96 and SIMON64/128
respectively. In addition, we use algorithm 2 of Matsui to attack 18, 23 and 27 rounds of
SIMECK32/64, SIMECK48/96 and SIMECK64/128 respectively, compare them with known
attacks on 18, 19 and 21 rounds SIMON32/64, SIMON48/96 and SIMON64/128 respectively.
In our construction a membership witness needs to be updated only a logarithmic number times in the number of subsequent element additions. Thus, an out-of-date witness can be easily made current. Vice versa, a verifier with an out-of-date accumulator value can still verify a current membership witness. These properties make our accumulator construction uniquely suited for use in distributed applications, such as blockchain-based public key infrastructures.
We first observe that compact RE is equivalent to a variant of the notion of indistinguishability obfuscation (iO)---which we refer to as puncturable iO---for the class of Turing machines without inputs. For the case of circuits, puncturable iO and iO are equivalent (and this fact is implicitly used in the powerful ``punctured program\'\' paradigm by Sahai and Waters [SW13]).
We next show the following:
- Impossibility in the Plain Model: Assuming the existence of subexponentially secure one-way functions, subexponentially-secure sublinear RE does not exists. (If additionally assuming subexponentially-secure iO for circuits we can also rule out polynomially-secure sublinear RE.) As a consequence, we rule out also puncturable iO for Turing machines (even those without inputs).
- Feasibility in the CRS model and Applications to iO for circuits: Subexponentially-secure sublinear RE in the CRS model and one-way functions imply iO for circuits through a simple construction generalizing GGM\'s PRF construction. Additionally, any compact (even with sublinear compactness) functional encryption essentially directly yields a sublinear RE in the CRS model, and as such we get an alternative, modular, and simpler proof of the results of [AJ15,BV15] showing that subexponentially-secure sublinearly compact FE implies iO.
- Applications to iO for Unbounded-input Turing machines: Subexponentially-secure compact RE for natural restricted classes of distributions over programs and inputs (which are not ruled out by our impossibility result, and for which we can give candidate constructions) imply iO for unbounded-input Turing machines. This yields the first construction of iO for unbounded-input Turing machines that does not rely on (public-coin) differing-input obfuscation.
combining the Simon and Speck block cipher. While the design allows a
smaller and more efficient hardware implementation, its security margins are not well understood. The lack of design rationals of its predecessors further leaves some uncertainty on the security of Simeck.
In this work we give a short analysis of the impact of the design changes by comparing the lower bounds for differential and linear characteristics with Simon. We also give a comparison of the effort of finding those bounds, which surprisingly is significant less for Simeck while covering a larger number of rounds.
Furthermore, we provide new differentials for Simeck which can cover
more rounds compared to previous results on Simon. Based on this we
mount key recovery attacks on 19/26/33 rounds of Simeck32/48/64,
which also give insights on the reduced key guessing effort due to the
different set of rotation constants.
mimics the visual appearance of another one. If such an attack is successful,
the integrity of what the user sees as well as the confidentiality of what she
inputs into the system can be violated by the adversary. A common example of
mobile application spoofing is a phishing attack where the adversary tricks the
user into revealing her password to a malicious application that resembles the
In this work, we propose a novel approach for addressing mobile application
spoofing attacks by leveraging the visual similarity of application screens. We
use deception rate as a novel metric for measuring how many users would confuse
a spoofing application for the genuine one. We conducted a large-scale online
study where participants evaluated spoofing samples of popular mobile
applications. We used the study results to design and implement a prototype
spoofing detection system, tailored to the estimation of deception rate for
mobile application login screens.