International Association for Cryptologic Research

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2013-11-17
01:17 [Pub][ePrint]

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.

2013-11-15
10:45 [Event][New]

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

2013-11-14
19:17 [Pub][ePrint]

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.

12:18 [Job][New]

The Computer Science and Engineering (CSE) Department at the University of Connecticut invites applications for a tenure-track faculty position at the assistant or associate professor level, with an expected start date of August 23, 2014. The research specialties of interest are:

1. Machine Learning,

2. Privacy, Cryptography or Computer Security, or

3. Techniques for the analysis of Big Data with applications in diverse areas including biomedical informatics.

The successful candidate will:

• Develop and sustain an internationally-recognized, externally-funded research program in one of these areas of interest;

• Teach undergraduate and graduate courses that meet the curricular needs of our CSE department;

• Provide service and leadership to all units of the University of Connecticut, to external academic and scientific communities, and to the general public.

Minimum Qualifications:

1. Completed all requirements for a Ph.D. in computing or a related discipline by the time of the appointment—equivalent foreign degrees are acceptable;

2. Research credentials in Computer Science, with a specialty in one of the topics prescribed above.

Preferred Qualifications:

1. A record of consistent, outstanding research contributions in one of the topics prescribed above;

2. Significant relevant teaching experience.

This is a 9-month, tenure-track position with an expected start date of August 23, 2014. The successful candidates primary academic

appointment will be at the Storrs campus with the option to work at UConns regional campuses across the state. Salary and rank will be

commensurate with qualifications.

To apply, applications must be submitted using Acade

07:17 [Pub][ePrint]

Encrypting information has been regarded as one of the most substantial approaches to protect users\' sensitive information in radically changing internet technology era. In prior research, researchers have considered similarity search over encrypted documents infeasible, because the single-bit difference of a plaintext would result in an enormous bits difference in the corresponding ciphertext. However, we propose a novel idea of Security Similarity Search (SSS) over encrypted documents by applying character-wise encryption with approximate string matching to keyword index search systems. In order to do this, we define the security requirements of similarity search over encrypted data, propose two similarity search schemes, and formally prove the security of the schemes. The first scheme is more efficient, while the second scheme achieves perfect similarity search privacy. Surprisingly, the second scheme turns out to be faster than other keyword index search schemes with keywordwise encryption, while enjoying the same level of security. The schemes of SSS support \"like query(\'ab%\')\" and a query with misprints in that

the character-wise encryption preserves the degree of similarity between two plaintexts, and renders approximate string matching between the corresponding ciphertexts possible without decryption.

07:17 [Pub][ePrint]

In a 2005 IACR report, Wang published an efficient identity-based key agreement protocol (IDAK) suitable for resource constraint devices.

The author shows that the IDAK key agreement protocol is secure in the Bellare-Rogaway model with random oracles and also provides an ad-hoc security proof claiming that the IDAK protocol is not vulnerable to Key Compromise Impersonation attacks.

In this report, we claim that the IDAK protocol is vulnerable to key-compromise impersonation attacks. Indeed, Wang\'s results are valid only for a passive adversary that can corrupt parties or reveal certain session-specific data but is not allowed to manipulate protocol transcripts; a model considering this type of adversary is unable to afford KCI resilience.

07:17 [Pub][ePrint]

In this paper, we perform a review of elliptic curve cryptography (ECC), as it is used in practice today, in order to reveal unique mistakes and vulnerabilities that arise in implementations of ECC. We study four popular protocols that make use of this type of public-key cryptography: Bitcoin, secure shell (SSH), transport layer security (TLS), and the Austrian e-ID card. We are pleased to observe that about 1 in 10 systems support ECC across the TLS and SSH protocols. However, we find that despite the high stakes of money, access and resources protected by ECC, implementations suffer from vulnerabilities similar to those that plague previous cryptographic systems.

07:17 [Pub][ePrint]

The literature on side-channel analysis describes numerous masking schemes designed to protect block ciphers at the implementation level. Such masking schemes typically require the computation of masked tables prior to the execution of an encryption function. In this paper we revisit an attack which directly exploits this computation in such a way as to recover all or some of the masks used. We show that securely implementing masking schemes is only possible where one has access to a significant amount of random numbers.

07:17 [Pub][ePrint]

The subject of this paper, an improbable implementation of a recently standardized cryptographic hash function on a thirty-five-year-old microcomputer, may strike some as unusual and recreative at best. In the tedious discipline of the process, however, lessons were learned in implementation trade-offs for basic cryptographic primitives which may prove interesting in the current context of securing (small to nano) machine to machine communications. More importantly, that such insights might stem out of revisiting how earlier computing platforms relate to the code written on them to cast a distant light on modern connections of code to material, historical and contextual factors certainly illuminates the joys of retrocomputing.

07:17 [Pub][ePrint]

In 2013, Joux and then Barbulsecu et al. presented new algorithms for computing discrete logarithms in finite fields of small characteristic. Shortly thereafter, Adj et al. presented a concrete analysis showing that, when combined with some steps from classical algorithms, the new algorithms render the finite field F_{3^{6*509}} weak for pairing-based cryptography. Granger and Zumbragel then presented a modification of the new algorithms that extends their effectiveness to a wider range of fields.

In this paper, we study the effectiveness of the new algorithms combined with a carefully crafted descent strategy for the fields F_{3^{6*1429}} and F_{2^{4*3041}}. The intractability of the discrete logarithm problem in these fields is necessary for the security of pairings derived from supersingular curves with embedding degree 6 and 4 defined, respectively, over F_{3^{1429}} and F_{2^{3041}}; these curves were believed to enjoy a security level of 192 bits against attacks by Coppersmith\'s algorithm. Our analysis shows that these pairings offer security levels of at most 91 and 129 bits, respectively, leading us to conclude that they are dead for pairing-based cryptography.

2013-11-13
07:17 [Pub][ePrint]

We introduce the problem of Multi-Input Functional Encryption, where a secret key SK_f can correspond to an n-ary function f that takes multiple ciphertexts as input. Multi-input functional encryption is a general tool for computing on encrypting data which allows for mining aggregate information from several different data sources (rather than just a single source as in single input functional encryption). We show wide applications of this primitive to running SQL queries over encrypted database, non-interactive differentially private data release, delegation of computation, etc.

We formulate both indistinguishability-based and simulation-based definitions of security for this notion, and show close connections with indistinguishability and virtual black-box definitions of obfuscation. Assuming indistinguishability obfuscation for circuits, we present constructions achieving indistinguishability security for a large class of settings. We show how to modify this construction to achieve simulation-based security as well, in those settings where simulation security is possible. Assuming differing-inputs obfuscation [Barak et al., FOCS\'01], we also provide a construction with similar security guarantees as above, but where the keys and ciphertexts are compact.