International Association for Cryptologic Research

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2012-11-14
09:55 [Job][New]

The Horst Görtz Institute for IT-Security (HGI) at Ruhr-University Bochum is one of Europe’s leading research centers in IT security. The DFG, or German Research Foundation, awarded more than €4 million to the HGI for the establishment of the interdisciplinary research training group “New Challenges for Cryptography in Ubiquitous Computing”. We are looking for candidates with outstanding Master/Diplom in the fields of computer science, electrical engineering, mathematics or related areas.

The research training group will study problems which are fundamental for securing the Internet of Things. The research is structured in three levels: cryptographic primitives, device and system level. The research topics range from cryptographic foundations such as fully homomorphic encryption for privacy in cloud computing, over security for medical implants to internet security solutions involving new national ID cards. A central goal of the doctoral training is an interdisciplinary and structured education at the highest scientific level. Establishing networks to top internationally research groups is part of the training.

A group of internationally renowned researchers together with excellent funding provides an extremely interesting scientific environment. The HGI is known for its good working atmosphere.

The Ruhr-University Bochum supports women‘s career development. Applications from women are thus explicitly welcome. In those areas in which women are underrepresented they will be considered preferentially according to the regulations of the „Landesgleichstellungsgesetz” if their abilities, aptitude and professional performance are equal with those of the fellow applicants unless reasons concerning the person of a fellow applicant are predominant.

In case of equal qualification, applications of severely disabled persons or persons that are regarded as being on a par with severely disable

06:25 [Job][New]

PhD students and post-docs who wish to do research on mathematical aspects of cryptography (most notably, noncommutative algebraic cryptography), are solicited.

The students will be hosted by and collaborate with Dr. Boaz Tsaban of the Department of Mathematics, Bar-Ilan University (BIU), and have the opportunity to interact with several crypto groups located in BIU.

There are two categories:

1. French citizens under 28 years old.

Details: http://u.cs.biu.ac.il/~tsaban/TXT/France-Israel.txt

2. Danish citizens.

Details: http://u.cs.biu.ac.il/~tsaban/Pdf/Danish-Israel.pdf

06:24 [Event][New]

Submission: 10 May 2013
From July 8 to July 10
Location: Ostrava, Czech Republic

2012-11-12
12:36 [Job][New]

There is one open postdoc position in the group of Dennis Hofheinz at the Karlsruhe Institute of Technology. The focus of our group is on all kinds of provable security, and in particular on public-key cryptography and cryptographic protocols.

Candidates should have a strong publication record. Knowledge of German is not required. There is funding for one year, with a possible extension. Review of applications starts immediately and will continue until the position is filled. The starting date is flexible.

2012-11-11
19:17 [Pub][ePrint]

We formalize a new cryptographic primitive, Message-Locked Encryption (MLE), where the key under which encryption and decryption are performed is itself derived from the message. MLE provides a way to achieve secure deduplication (space-efficient secure outsourced storage), a goal currently targeted by numerous cloud-storage providers. We provide definitions both for privacy and for a form of integrity that we call tag consistency. Based on this foundation, we make both practical and theoretical contributions. On the practical side, we provide ROM security analyses of a natural family of MLE schemes that includes deployed schemes. On the theoretical side the challenge is standard model solutions, and we make connections with deterministic encryption, hash functions secure on correlated inputs and the sample-then-extract paradigm to deliver schemes under different assumptions and for different classes of message sources. Our work shows that MLE is a primitive of both practical and theoretical interest.

19:17 [Pub][ePrint]

This paper presents the Tate pairing computation on generalized Huff curves proposed by Wu and Feng in \\cite{Wu}. In fact, we extend the results of the Tate pairing computation on the standard Huff elliptic curves done previously by Joye, Tibouchi and Vergnaud in \\cite{Joux}. We show that the addition step of the Miller loop can be performed in $1\\mathbf{M}+(k+15)\\mathbf{m}+2\\mathbf{c}$ and the doubling one in $1\\mathbf{M} + 1\\mathbf{S} + (k + 12) \\mathbf{m} + 5\\mathbf{s} + 2\\mathbf{c}$ on the generalized Huff curve.

19:17 [Pub][ePrint]

In this paper, we provide some cryptanalytic results for

double-block-length (DBL) hash modes of block ciphers, MDC-4. Our

preimage attacks follow the framework of Knudsen et al.\'s

time/memory trade-off preimage attack on MDC-2. We find how to apply

it to our objects. When the block length of the underlying block

cipher is $n$ bits, the most efficient preimage attack on MDC-4

requires time and space about $2^{3n/2}$, which is to be compared to

the previous best known preimage attack having time complexity of

$2^{7n/4}$. Additionally, we propose an enhanced version of MDC-4,

MDC-4$^*$ based on a simple idea. It is secure against our preimage

attack and previous attacks and has the same efficiency as MDC-4.

19:17 [Pub][ePrint]

A double-block-length (DBL) hash mode of block ciphers, MJH has been

proved to be collision-resistant in the ideal cipher model upto

$2^{2n/3- \\log n}$ queries. In this paper we provide first

cryptanalytic results for MJH. We show that a collision attack on

MJH has the time complexity below the birthday bound. When block

ciphers with 128-bit blocks are used, it has time complexity around

$2^{124}$, which is to be compared to the birthday attack having

complexity $2^{128}$. We also give a preimage attack on MJH. It has

the time complexity of $2^{3n/2+1}$ with $n$-bit block ciphers,

which is to be compared to the brute force attack having complexity

$2^{2n}$.

19:17 [Pub][ePrint]

Attribute-Based Encryption (ABE) is a promising cryptographic primitive which significantly enhances the versatility of access control mechanisms. Due to the high expressiveness of ABE policies, the computational complexities of ABE key-issuing (by Attribute Authorities (AAs)) and decryption (by eligible users) are getting prohibitively high. Despite that the existing Outsourced ABE solutions are able to offload some intensive computing tasks to a third party, for example, a cloud, so to relieve the local burden of eligible users during decryption, the high computational complexity of the key-issuing at the AAs has yet to be addressed, while an ABE system will continue to grow with more users being included, and with the user revocation being considered in practice which will trigger more key (re-)issuing.

Aiming at tackling the challenges above, for the first time, we propose a Secure Outsourced ABE system, which not only supports secure outsourced decryption, but also provides secure outsourced key-issuing. Unlike the current outsourced ABE systems, our new method offloads all access policy and attribute related operations in the key-issuing process or decryption to a Key Generation Service Provider (KGSP) and a Decryption Service Provider (DSP), respectively, leaving only a constant number of simple operations for the AAs and eligible users to perform locally. Furthermore, we show that both outsourcing processes (to KGSP and to DSP) are secure, namely, the KGSP and the DSP would not be able to recover the keys or decrypt the ciphertexts, respectively.

In addition, we consider the scenario that a KGSP or DSP may be dishonest and could maliciously generate some incorrect returning values rather than following the outsourced operations. Therefore, in this paper, we also propose another ABE construction which allows the AAs and eligible users to check the correctness of outsourced operations in an efficient way. The security of the construction is analyzed under a recently formalized model called Refereed Delegation of Computation (RDoC).

19:17 [Pub][ePrint]

In this paper we present a study of the complexity of the Blum-Kalai-Wasserman (BKW) algorithm when applied to the Learning with Errors (LWE) problem, by providing refined estimates for the data and computational effort requirements for solving concrete instances of the LWE problem. We apply this refined analysis to suggested parameters for various LWE-based cryptographic schemes from the literature and, as a result, provide new upper bounds for the concrete hardness of these LWE-based schemes.

19:17 [Pub][ePrint]

We present high performance non-deterministic fully-homomorphic methods for practical randomization of data (over commutative ring), and symmetric-key encryption of random mod-N data (over ring of reidues mod-N) well suited for crypto applications. These methods secure, for example, the multivariate input or the coefficients of a polynomial function running in an open untrusted environment. We show that random plaintext is the sufficient condition for proof of security for the homomorphic encryption. The efficient nature of the methods - one large-numbers multiplication per encryption and six for the product of two encrypted values - motivates and enables the use of low cost collaborative security platforms for crypto applications such as keyed-hash or private key derivation algorithms. Such a platform is comprised of a low-cost and low performance security element supported by an untrusted high performance server running the homomorpic algorithms. The methods employed may also provide enhanced protection for some existing crypto algorithms against certain attacks. Specifically, it is shown how to secure OSS public-key signature against Pollard attack. Further, we demonstrate how the homomorphic randomization of data can offer protection for an AES-key against side-channel attacks. Finally, the methods provide both fault detection and verification of computed-data integrity.