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04:17 [Pub][ePrint] On the Power of Rewinding Simulators in Functional Encryption, by Angelo De Caro and Vincenzo Iovino

  In the recent years, functional encryption (FE)

has received a lot of attention due to its

versatility and unique challenges it poses.

In FE, a receiver with secret-key $sk_y$ can compute from an

encryption of $x$ the value $F(y,x)$ for some

functionality $F$. The seminal work

of Boneh, Sahai and Waters [TCC\'11] showed

that for functional encryption the indistinguishability

notion of security (IND-Security) is weaker then simulation-based

and, moreover, showed that simulation-based security

is impossible to achieve even in weaker settings.

This has opened up the door to a plethora of papers,

showing feasibility and new impossibility results,

having in common the pursuit of a reasonable

and achievable simulation-based security definition.

With the same aim, in this work, we propose a new

simulation-based security definition that we call

{\\em rewinding simulation-based security} (RSIM-Security).

Rewinding arguments have been used

in all sorts of interactive protocols

and have been shown to be highly useful to argue

security. We exploit this power allowing

the simulator to rewind the adversary

under specific constraints.

Specifically, the simulator will be able to rewind

the adversary an arbitrary number of times

under the constraint that

the simulator does not learn more

information about the challenge messages than the


Under our new definition we show that:

(1) IND-Security is equivalent

to RSIM-Security

for {\\em predicate encryption with public-index}

(i.e. Attribute-Based Encryption)

in the {\\em standard model}. Previous results

showed impossibility results in the standard


This {\\em equivalence} is the best one can hope

for general functionalities due to the counterexample of Boneh \\etal.

(2) Notwithstanding, we show that for notable classes of predicates (e.g., Anonymous IBE, inner-product over $\\Z_2$, any

family of circuits in $\\NC_0$, and monotone conjunctive Boolean formulae)

IND-Security is equivalent

to RSIM-Security in the standard


Previous results showed impossibility results in the

standard model and the positive results were set

either in the random oracle or in more restricted security


(3) On the negative side,

we show that our security

definition cannot be achieved

by functional encryption schemes for

general functionalities (specifically, functionalities that compute a pseudo-random function) in the adaptive setting. The argument

we use is to some extent the {\\em dual}

of that used by

Agrawal, Gorbunov, Vaikuntanathan, and Wee

[CRYPTO\'13] in the non-adaptive setting.

(4) We complete the picture showing the achievability of unbounded simulation (USIM) answering positively to a question posed by Agrawal, Gorbunov, Vaikuntanathan and Wee [CRYPTO 2013].

04:17 [Pub][ePrint] Dietary Recommendations for Lightweight Block Ciphers: Power, Energy and Area Analysis of Recently Developed Architectures, by Lejla Batina and Amitabh Das and Baris Ege and Elif Bilge Kavun and Nele

  In this paper we perform a comprehensive area, power, and energy analysis of some of the most recently-developed lightweight block ciphers and we compare them to the standard AES algorithm. We do this for several different architectures of the considered block ciphers. Our evaluation method consists of estimating the pre-layout power consumption and the derived energy using Cadence Encounter RTL Compiler and ModelSIM simulations.We show that the area is not always correlated to the power and energy consumption, which is of importance for mobile battery-fed devices. As a result, this paper can be used to make a choice of architecture when the algorithm has already been fixed; or it can help deciding which algorithm to choose based on energy and key/block length requirements.

04:17 [Pub][ePrint] Obfuscation-based Non-black-box Simulation and Four Message Concurrent Zero Knowledge for NP, by Omkant Pandey and Manoj Prabhakaran and Amit Sahai

  As recent studies show, the notions of *program obfuscation* and *zero

knowledge* are intimately connected. In this work, we explore this connection further, and prove the following general result. If there exists *differing input obfuscation* (diO) for the class of all polynomial time Turing machines, then there exists a *four message, fully concurrent zero-knowledge* proof system for all languages in NP with negligible soundness error. This result is constructive: given diO, our reduction yields an explicit protocol along with an *explicit* simulator that is ``straight line\'\' and runs in strict

polynomial time.

Our reduction relies on a new non-black-box simulation technique which does not use the PCP theorem. In addition to assuming diO, our reduction also assumes (standard and polynomial time) cryptographic assumptions such as collision-resistant hash functions.

The round complexity of our protocol also sheds new light on the *exact* round complexity of concurrent zero-knowledge. It shows, for the first time, that in the realm of non-black-box simulation, concurrent zero-knowledge may not necessarily require more rounds than *stand alone* zero-knowledge!

04:17 [Pub][ePrint] Improving security and efficiency for multi-authority access control system in cloud storage, by Qi Li and Jianfeng Ma and Rui Li and Ximeng Liu and Jinbo Xiong

  Multi-Authority Attribute-Based Encryption (MA-ABE) is an emerging cryptographic primitive for enforcing fine-grained attribute-based access control on the outsourced data in cloud storage. However, most of the previous multi-authority attribute-based systems are either proven security in a weak model or lack of efficiency in user revocation. In this paper, we propose a novel multi-authority attribute-based data access control system for cloud storage. We construct a new multi-authority CP-ABE scheme with decryption outsourcing. We largely eliminate the decryption overhead for users by outsourcing the undesirable bilinear pairing operations to the cloud servers. The proposed scheme is proven adaptively secure in the standard model and supports any monotone access policy. We also design an efficient attribute-level user revocation approach with less computation cost. The security analysis, numeral comparisons indicate that the proposed system is secure, efficient and scalable.

04:17 [Pub][ePrint] A Meet-in-the-middle Attack on Round-Reduced mCrypton, by Yonglin Hao, Dongxia Bai

  The meet-in-the-middle (MITM) attack on AES is a great success.

In this paper, we apply the method to the lightweight SPN block cipher mCrypton.

We prove that the multiset technique used to analyze AES can not be applied directly to mCrypton due to the scarcity of information. As a solution, we replace the unordered multiset with the ordered sequence. We lower the memory requirement from $2^{100}$ to $2^{44}$ using the efficient differential enumeration technique.

Based on these modifications, we construct a MITM attack on 7-round mCrypton-64/96/128 with complexities

of $2^{44}$ 64-bit blocks and $2^{57}$ encryptions.

We further extend the attack to 8 and 9 rounds for mCrypton-128 by adding some key-bridging techniques. The 8-round attack requires $2^{44}$ blocks and $2^{96}$ encryptions while the 9-round attack needs $2^{120}$ blocks and $2^{116}$ encryptions.

04:17 [Pub][ePrint] Practical Signatures from the Partial Fourier Recovery Problem, by Jeff Hoffstein and Jill Pipher and John Schanck and Joseph H. Silverman and William Whyte

  Abstract. We present PASSSign, a variant of the prior PASS and PASS-2 proposals, as a candidate for a practical post-quantum signature scheme. Its hardness is based on the problem of recovering a ring element with small norm from an incomplete description of its Chinese remainder representation. For our particular instantiation, this corresponds to the recovery of a signal with small infinity norm from a limited set of its Fourier coefficients.

The key improvement over previous versions of PASS is the introduction of a rejection sampling technique from Lyubashevsky (2009) which assures that transcript distributions are completely decoupled from the keys that generate them.

Although the scheme is not supported by a formal security reduction, we present extensive arguments for its security and derive concrete parameters based on the performance of state of the art lattice reduction and enumeration techniques.

04:17 [Pub][ePrint] A Revocable Online-Offline Certificateless Signature Scheme without Pairing, by Karthik Abinav and Saikrishna Badrinarayanan and C. Pandu Rangan and S. Sharmila Deva Selvi and S. Sree Vivek and Vivek

  Certificateless Public key Cryptography is a widely studied paradigm due to its advantages of not

having the key-escrow problem and the lack of use of certificates. Online-Offline signature schemes are

extremely relevant today because of their great practical applications. In an online-offline signature

scheme all the heavy computation is done on powerful processors and stored securely in the offline

phase, and the online component requires only light computation. Hence, it is widely used in several

low-resource devices like mobile phones, etc. Revocation is another important problem of wide interest

as it helps to keep a check on misbehaving users. Currently, there are very few revocable certificateless

signature schemes in the literature. We have addressed some of the limitations of the previously existing

schemes and designed a new model for the same that involves periodic time generated keys. We present

a revocable online-offline certificateless signature scheme without pairing. Pairing, though a very useful

mathematical function, comes at the cost of heavy computation. Our scheme is proved secure in the

random oracle model using a tight security reduction to the computational Diffie-Hellman problem.


  In this paper, we propose a new signature scheme connecting two private keys and two public keys based on general non-commutative division semiring. The key idea of our technique engrosses three core steps. In the first step, we assemble polynomials on additive structure of non-commutative division semiring and take them as underlying work infrastructure. In the second step, we generate first set of private and public key pair using polynomial symmetrical decomposition problem. In the third step, we generate second set of private and public key pair using discrete logarithm. We use factorization theorem to generate the private key in discrete logarithm problem. By doing so, we can execute a new signature scheme on multiplicative structure of the semiring using multiple private keys. The security of the proposed signature scheme is based on the intractability of the Polynomial Symmetrical Decomposition Problem and discrete logarithm problem over the given non-commutative division semiring. Hence, this signature scheme is so much strong in security point of view.

01:17 [Pub][ePrint] An efficient FHE proposal based on the hardness of solving systems of nonlinear multivariate equations (II), by GĂ©rald Gavin

  We propose a general framework to develop fully homomorphic encryption schemes (FHE) without using Gentry\'s technique. Initially, a private-key cryptosystem

is built over $\\mathbb{Z}_n$

($n$ being an RSA modulus). An encryption of $x\\in \\mathbb{Z}_n$

is a randomly chosen vector $e$ such that $\\Phi(e)=x$ where $\\Phi$ is a secret multivariate polynomial.

This private-key cryptosystem is not homomorphic in the sense that the vector sum is not a homomorphic operator. Non-linear homomorphic operators are then

developed. The security relies on the difficulty of solving systems of nonlinear equations (which is a $\\mathcal{NP}$-complete problem). While the security of our scheme has not been reduced to a provably hard instance of this problem,

its security is globally investigated.

10:45 [Event][New] CloudCom 2013: IEEE CloudCom 2013 (5th IEEE International Conference on Cloud Computing)

  Submission: 2 December 2013
From December 2 to December 5
Location: Bristol, United Kingdom
More Information:

19:17 [Pub][ePrint] On the Resilience and Uniqueness of CPA for Secure Broadcast, by Chris Litsas and Aris Pagourtzis and Giorgos Panagiotakos and Dimitris Sakavalas

  We consider the Secure Broadcast problem in incomplete networks. We study the resilience of the Certified Propagation Algorithm (CPA),

which is particularly suitable for ad hoc networks. We address the issue of determining the maximum number of corrupted players $t^{\\mathrm{CPA}}_{\\max}$ that CPA can tolerate under the $t$-locally bounded adversary model, in which the adversary may corrupt at most

$t$ players in each player\'s neighborhood. For any graph $G$ and dealer-node $D$ we provide upper and lower bounds on $t^{\\mathrm{CPA}}_{\\max}$ that can be efficiently computed in terms of a graph theoretic parameter that we introduce in this work. Along the way we obtain an efficient 2-approximation algorithm for $t^{\\mathrm{CPA}}_{\\max}$. We further introduce two more graph parameters, one of which matches $t^{\\mathrm{CPA}}_{\\max}$exactly. Our approach allows to provide an affirmative answer to the open problem of CPA Uniqueness posed by Pelc and Peleg in 2005.