International Association for Cryptologic Research

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2014-01-15
22:17 [Pub][ePrint] Practical polynomial time solutions of several major problems in noncommutative-algebraic cryptography, by Boaz Tsaban

  We provide new provable polynomial time solutions

of a number of problems in noncommutative-algebraic cryptography.

In contrast to the linear centralizer method of \\cite{LinCent}, the new method is

very simple: In order to solve linear equations on matrices

restricted to matrix groups, solve them over the generated

algebras. We name this approach the \\emph{algebraic span method}.

The resulting algorithms are have substantially better performance than those of \\cite{LinCent}.

These algorithms constitute cryptanalyses of the motivating protocols that

cannot be foiled by changing the distributions used in the protocols, and are

practical for most affordable parameter settings.



16:49 [Event][New]

 

16:17 [Pub][ePrint] A Fast Modular Reduction Method, by Zhengjun Cao and Ruizhong Wei and Xiaodong Lin

  We put forth a lookup-table-based modular reduction method which partitions the binary string of an integer to be reduced into blocks according to its runs. Its complexity depends on the amount of runs in the binary string. We show that the new reduction is almost twice as fast as the popular Barrett\'s reduction, and provide a thorough complexity analysis of the method.



07:05 [PhD][Update] Serge Vaudenay: The Security of Cryptographic Primitives

  Name: Serge Vaudenay
Topic: The Security of Cryptographic Primitives
Category:secret-key cryptography

Description: In the early fifties, Claude Shannon initiated the theory of cryptographic primitives. He defined the notion of diffusion and confusion. However, this theory did not developed very much until nowadays. Recently, the differential cryptanalysis and the linear cryptanalysis gave a significant advance in the analysis of the primitives. Security criteria for confusion, essentially nonlinearity criteria, has been proposed. In this thesis, we show how to define a notion of complexity on the graph structure of the primitives and how to study it. This gives security criteria of the computational network. We propose new criteria for diffusion. Finally, we unify the two types of cryptanalysis, getting rid of their linear aspects by a statistical approach.[...]


04:17 [Pub][ePrint] Homomorphic AES Evaluation using NTRU, by Yarkin Doroz and Yin Hu and Berk Sunar

  Since its introduction more than a decade ago the homomorphic properties of the NTRU encryption scheme have gone largely ignored. A variant of NTRU proposed by Stehle and Steinfeld was recently extended into a full fledged multi-key fully homomorphic encryption scheme by Alt-Lopez, Tromer and Vaikuntanathan (ATV). This NTRU based FHE presents a viable alternative to the currently dominant BGV style FHE schemes. While the scheme appears to be more efficient, a full implementation and comparison to BGV style implementations has been missing in the literature. In this work, we develop a customized implementation of the ATV scheme. First parameters are selected to yield an efficient and yet secure ATV instantiation. We present an analysis of the noise growth that allows us to formulate a modulus cutting strategy for arbitrary circuits. Furthermore, we introduce a specialization of the ring structure that allows us to drastically reduce the public key size making evaluation of deep circuits such as the AES block cipher viable on a standard computer with a reasonable amount of memory. Moreover, with the modulus specialization the need for key switching is eliminated. Finally, we present a generic bit-sliced implementation of the ATV scheme that embodies a number of optimizations. To assess the performance of the scheme we homomorphically evaluate the full 10 round AES circuit in 31 hours with 2048 message slots resulting in 55 sec per AES block evaluation time.





2014-01-14
16:17 [Pub][ePrint] Extending and Applying a Framework for the Cryptographic Verification of Java Programs., by Ralf Küsters and Enrico Scapin and Tomasz Truderung and Jürgen Graf

  In our previous work, we have proposed a framework which allows tools

that can check standard noninterference properties but a priori

cannot deal with cryptography to establish cryptographic

indistinguishability properties, such as privacy properties, for

Java programs. We refer to this framework as the CVJ framework

(Cryptographic Verification of Java Programs) in this paper.

While so far the CVJ framework directly supports public-key

encryption (without corruption and without a public-key

infrastructure) only, in this work we further instantiate the

framework to support, among others, public-key encryption and

digital signatures, both with corruption and a public-key

infrastructure, as well as (private) symmetric encryption. Since

these cryptographic primitives are very common in security-critical

applications, our extensions make the framework much more widely

applicable.

To illustrate the usefulness and applicability of the extensions

proposed in this paper, we apply the framework along with the tool

Joana, which allows for the fully automatic verification of

noninterference properties of Java programs, to establish

cryptographic privacy properties of a (non-trivial) cloud storage

application, where clients can store private information on a remote

server.



13:17 [Pub][ePrint] Extending and Applying a Framework for the Cryptographic Verification of Java Programs., by Ralf K\\\"usters and Enrico Scapin and Tomasz Truderung and J\\\"urgen Graf

  In our previous work, we have proposed a framework which allows tools

that can check standard noninterference properties but a priori

cannot deal with cryptography to establish cryptographic

indistinguishability properties, such as privacy properties, for

Java programs. We refer to this framework as the CVJ framework

(Cryptographic Verification of Java Programs) in this paper.

While so far the CVJ framework directly supports public-key

encryption (without corruption and without a public-key

infrastructure) only, in this work we further instantiate the

framework to support, among others, public-key encryption and

digital signatures, both with corruption and a public-key

infrastructure, as well as (private) symmetric encryption. Since

these cryptographic primitives are very common in security-critical

applications, our extensions make the framework much more widely

applicable.

To illustrate the usefulness and applicability of the extensions

proposed in this paper, we apply the framework along with the tool

Joana, which allows for the fully automatic verification of

noninterference properties of Java programs, to establish

cryptographic privacy properties of a (non-trivial) cloud storage

application, where clients can store private information on a remote

server.



01:17 [Pub][ePrint]

 



2014-01-13
22:17 [Pub][ePrint] A Secure Text Messaging Protocol, by Gary Belvin

  Mobile text messages are currently vulnerable to inspection, modification, and replay by network operators and those that influence network operators. This paper describes a set of protocols that provide end-to-end message confidentiality, integrity, and authenticity over the high latency, low bandwidth, Short Message Service provided by GSM networks.





2014-01-12
16:17 [Pub][ePrint] Channel Equalization for Side Channel Attacks, by Colin O\'Flynn and Zhizhang (David) Chen

  This paper introduces the use of channel equalization as a method of simplifying side channel analysis attacks, by eeffectively collapsing all points in a power measurement trace into a single random variable. This uses a simple Finite Impulse Response (FIR) linear equalizer, which has been studied extensively in communications systems. In addition the estimation of a channel model is used in developing the Channel Estimation Analysis (CEA), which is a generic attack requiring similar assumptions to the Correlation Power Analysis (CPA) attack. Both channel equalization and the CEA attack are straight-forward to apply to real systems, and Python examples are provided. Results of attacking unprotected AES-128 and protected AES-256RSM on a microcontroller are provided.



16:17 [Pub][ePrint] General Impossibility of Group Homomorphic Encryption in the Quantum World, by Frederik Armknecht and Tommaso Gagliardoni and Stefan Katzenbeisser and Andreas Peter

  Group homomorphic encryption represents one of the most important building blocks in modern cryptography. It forms the basis of widely-used, more sophisticated primitives, such as CCA2-secure encryption or secure multiparty computation. Unfortunately, recent advances in quantum computation show that many of the existing schemes completely break down once quantum computers reach maturity (mainly due to Shor\'s algorithm). This leads to the challenge of constructing quantum-resistant group homomorphic cryptosystems.

In this work, we prove the general impossibility of (abelian) group homomorphic encryption in the presence of quantum adversaries, when assuming the IND-CPA security notion as the minimal security requirement. To this end, we prove a new result on the probability of sampling generating sets of finite (sub-)groups if sampling is done with respect to an arbitrary, unknown distribution. Finally, we provide a sufficient condition on homomorphic encryption schemes for our quantum attack to work and discuss its satisfiability in non-group homomorphic cases. The impact of our results on recent fully homomorphic encryption schemes poses itself as an open question.