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21:17 [Pub][ePrint] The leaking battery A privacy analysis of the HTML5 Battery Status API, by Lukasz Olejnik and Gunes Acar and Claude Castelluccia and Claudia Diaz

  We highlight the privacy risks associated with the HTML5 Battery Status API. We put special focus on its implementation in the Firefox browser. Our study shows that websites can discover the capacity of users\' batteries by exploiting the high precision readouts provided by Firefox on Linux. The capacity of the battery, as well as its level, expose a fingerprintable surface that can be used to track web users in short time intervals. Our analysis shows that the risk is much higher for old or used batteries with reduced capacities, as the battery capacity may potentially serve as a tracking identifier. The fingerprintable surface of the API could be drastically reduced without any loss in the API\'s functionality by reducing the precision of the readings. We propose minor modifications to Battery Status API and its implementation in the Firefox browser to address the privacy issues presented in the study. Our bug report for Firefox was accepted and a fix is deployed.

21:17 [Pub][ePrint] Generalised tally-based decoders for traitor tracing and group testing, by Boris Skoric and Wouter de Groot

  We propose a new type of score function for Tardos traitor tracing codes. It is related to the recently introduced tally-based score function, but it utilizes more of the information available to the decoder. It does this by keeping track of sequences of symbols in the distributed codewords instead of looking at columns of the code matrix individually.

We derive our new class of score functions from a Neyman-Pearson hypothesis test and illustrate its performance with simulation results.

Finally we derive a score function for (medical) group testing applications.

21:17 [Pub][ePrint] An Authentication Code over Galois Rings with Optimal Impersonation and Substitution Probabilities, by Juan Carlos Ku-Cauich Guillermo Morales-Luna Horacio Tapia-Recillas

  A new systematic authentication scheme based on the Gray map

over Galois rings is introduced. The Gray map determines an isometry between

the Galois ring and a vector space over a Galois eld. The introduced code

attains optimal impersonation and substitution probabilities.

21:17 [Pub][ePrint] Construction of Arithmetic Secret Sharing Schemes by Using Torsion Limits, by Seher Tutdere and Osmanbey Uzunkol

  Recent results of Cascudo, Cramer, and Xing on the construction of arithmetic secret sharing schemes are improved by using some new bounds on the torsion limits of algebraic function fields. Furthermore, new bounds on the torsion limits of certain towers of function fields are given.

21:17 [Pub][ePrint] Statistical Concurrent Non-malleable Zero-knowledge from One-way Functions, by Susumu Kiyoshima

  Concurrent non-malleable zero-knowledge (CNMZK) protocols are zero-knowledge protocols that are secure even against adversaries that interact with multiple provers and verifiers simultaneously. Recently, the first statistical CNMZK argument for NP was constructed under the DDH assumption (Orlandi el al., TCC\'14).

In this paper, we construct a statistical CNMZK argument for NP assuming only the existence of one-way functions. The security is proven via black-box simulation, and the round complexity is poly(n). Under the existence of collision-resistant hash functions, the round complexity can be reduced to w(log n), which is known to be essentially optimal for black-box concurrent zero-knowledge protocols.

21:17 [Pub][ePrint] Who watches the watchmen? : Utilizing Performance Monitors for Compromising keys of RSA on Intel Platforms, by Sarani Bhattacharya, Debdeep Mukhopadhyay

  Asymmetric-key cryptographic algorithms when implemented

on systems with branch predictors, are subjected

to side-channel attacks

exploiting the deterministic branch

predictor behavior due to their key-dependent input sequences. We show that branch predictors can also

leak information through the hardware

performance monitors which are

accessible by an adversary at the

user-privilege level. This paper presents

an iterative attack which target the

key-bits of 1024 bit RSA, where in

offline phase, the system\'s underlying

branch predictor is approximated

by a theoretical predictor in literature.

Subsimulations are performed

to classify the message-space into

distinct partitions based on the event

branch misprediction and the target key

bit value. In online phase, we ascertain

the secret key bit using branch mispredictions

obtained from the hardware performance

monitors which reflect the information of branch

miss due to the underlying predictor hardware.

We theoretically prove that the probability

of success of the attack is equivalent to the accurate

modelling of the theoretical predictor to the underlying system predictor. Experimentations reveal that the

success-rate increases with message-count and reaches such a significant value so as to consider side-channel

from the performance counters as a real threat

to RSA-like ciphers due

to the underlying branch predictors and

needs to be considered for developing secured-systems.

21:17 [Pub][ePrint] Random Digit Representation of Integers, by Nicolas Méloni and M. Anwar Hasan

  Modular exponentiation is core to today\'s main stream

public key cryptographic systems. In this article, we generalize the

classical fractional $w$NAF method for modular exponentiation -- the

classical method uses a digit set of the form $\\{1,3,\\dots,m\\}$

which is extended here to any set of odd integers of the form

$\\{1,d_2,\\dots, d_n\\}$. We give a formula for the average density of

non-zero terms in this new representation and discuss its asymptotic

behavior when those digits are randomly chosen from a given set. We

also propose a specific method for the precomputation phase of the

exponentiation algorithm.

21:17 [Pub][ePrint] Design, Evaluation and Optimization of Physical Unclonable Functions based on Transient Effect Ring Oscillators, by Abdelkarim Cherkaoui, Lilian Bossuet and Cédric Marchand

  This paper proposes a theoretical study and a full

overview of the design, evaluation and optimization of a PUF

based on transient element ring oscillators (TERO-PUF). We

show how, by following some simple design rules and strategies,

designers can build and optimize a TERO-PUF with state of the

art PUF characteristics in a standard CMOS technology. To this

end, we analyzed the uniqueness, steadiness and randomness of

responses generated from 30 test chips in a CMOS 350nm process

in nominal and corner voltage and temperature conditions.

Response generation schemes are proposed to optimize PUF

performances and reduce its area without noticeable loss in its

output quality. In particular, we show that the large area of the

basic blocks in the TERO-PUF is balanced by the high level

of entropy extracted in each basic block. Thus, the length of

the response to the same challenge is increased. Guidelines are

provided to balance reliability and randomness of the responses

and the design area.

21:17 [Pub][ePrint] Automated Analysis and Synthesis of Authenticated Encryption Schemes, by Viet Tung Hoang and Jonathan Katz and Alex J. Malozemoff

  Authenticated encryption (AE) schemes are symmetric-key encryption schemes ensuring strong notions of confidentiality and integrity. Although various AE schemes are known, there remains significant interest in developing schemes that are more efficient, meet even stronger security notions (e.g., misuse-resistance), or satisfy certain non-cryptographic properties (e.g., being patent-free).

We present an automated approach for analyzing and synthesizing blockcipher-based AE schemes, significantly extending prior work by Malozemoff et al. (CSF 2014) who synthesize encryption schemes satisfying confidentiality only. Our main insight is to restrict attention to a certain class of schemes that is expressive enough to capture several known constructions yet also admits automated reasoning about security. We use our approach to generate thousands of AE schemes with provable security guarantees, both known (e.g., variants of OCB and CCM) and new. Implementing two of these new schemes, we find their performance competitive with state-of-the-art AE schemes.

21:17 [Pub][ePrint] Ed448-Goldilocks, a new elliptic curve, by Mike Hamburg

  Many papers have proposed elliptic curves which are faster and easier to implement than the NIST prime-order curves. Most of these curves have had fields of size around $2^256$, and thus security estimates of around 128 bits. Recently there has been interest in a stronger curve, prompting designs such as Curve41417 and Microsoft\'s pseudo-Mersenne-prime curves.

Here I report on the design of another strong curve, called Ed448-Goldilocks. Implementations of this curve can perform very well for its security level on many architectures. As of this writing, this curve is favored by IRTF CFRG for inclusion in future versions of TLS along with Curve25519.

21:17 [Pub][ePrint] Practical Round-Optimal Blind Signatures in the Standard Model, by Georg Fuchsbauer and Christian Hanser and Daniel Slamanig

  Round-optimal blind signatures are notoriously hard to construct in the standard model, especially in the malicious-signer model, where blindness must hold under adversarially chosen keys. This is substantiated by several impossibility results. The only construction that can be termed theoretically efficient, by Garg and Gupta (Eurocrypt\'14), requires complexity leveraging, inducing an exponential security loss.

We present a construction of practically efficient round-optimal blind signatures in the standard model. It is conceptually simple and builds on the recent structure-preserving signatures on equivalence classes (SPS-EQ) from Asiacrypt\'14. While the traditional notion of blindness follows from standard assumptions, we prove blindness under adversarially chosen keys under an interactive variant of DDH. However, we neither require non-uniform assumptions nor complexity leveraging.

We then show how to extend our construction to partially blind signatures and to blind signatures on message vectors, which yield a construction of one-show anonymous credentials à la \"anonymous credentials light\" (CCS\'13) in the standard model.

Furthermore, we give the first SPS-EQ construction under non-interactive assumptions and show how SPS-EQ schemes imply conventional structure-preserving signatures, which allows us to apply optimality results for the latter to SPS-EQ.