International Association for Cryptologic Research

# IACR News Central

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2014-06-21
06:17 [Pub][ePrint]

A homomorphic signature scheme for a class of functions $\\mathcal{C}$ allows a client to sign and upload elements of some data set $D$ on a server. At any later point, the server can derive a (publicly verifiable) signature that certifies that some $y$ is the result computing some $f\\in\\mathcal{C}$ on the basic data set $D$. This primitive has been formalized by Boneh and Freeman (Eurocrypt 2011) who also proposed the only known construction for the class of multivariate polynomials of fixed degree $d\\geq 1$. In this paper we construct new homomorphic signature schemes for such functions. Our schemes provide the first alternatives to the one of Boneh-Freeman, and improve over their solution in three main aspects. First, our schemes do not rely on random oracles. Second, we obtain security in a stronger fully-adaptive model: while the solution of Boneh-Freeman requires the adversary to query messages in a given data set all at once, our schemes can tolerate adversaries that query one message at a time, in a fully-adaptive way. Third, signature verification is more efficient (in an amortized sense) than computing the function from scratch. The latter property opens the way to using homomorphic signatures for publicly-verifiable computation on outsourced data. Our schemes rely on a new assumption on leveled graded encodings which we show to hold in a generic model.

06:17 [Pub][ePrint]

Cipher-policy attribute-based encryption (CP-ABE) is a more

efficient and flexible encryption system as the encryptor can control the access structure when encrypting a message. In this paper, we propose a privacy-preserving decentralized CP-ABE (PPDCP-ABE) scheme where the central authority is not required, namely each authority can work independently without the cooperation to initialize the system. Meanwhile, a user can obtain secret keys from multiple authorities without releasing his global identifier (GID) and attributes to them. This is contrasted to the previous privacy-preserving multi-authority ABE (PPMA-ABE) schemes where a user can obtain secret keys from multiple authorities with them knowing his attributes and a central authority is required. However, some sensitive attributes can also release the user\'s identity information. Hence, contemporary PPMA-ABE schemes cannot fully protect users\' privacy as multiple authorities can cooperate to identifier a user by collecting and analyzing his attributes. Therefore, it remains a challenging and important work to construct a PPMA-ABE scheme where the central authority is not required and both the identifiers and the attributes are considered

06:17 [Pub][ePrint]

A Ciphertext-Policy Attribute-Based Encryption (CP-ABE) system extracts the decryption keys over attributes shared by multiple users. It brings plenty of advantages in ABE applications. CP-ABE enables fine-grained access control to the encrypted data for commercial applications. There has been significant progress in CP-ABE over two properties called traceability and large universe in the past few years, which enlarges the commercial applications of CP-ABE. Due to the nature of CP-ABE, it is difficult to identify the original key owner from an exposed key since the decryption privilege is shared by multiple users who have the same attributes. Thus, it is necessary for ABE applications to add the property of traceability to find out the malicious users who intentionally leak the partial or modified decryption keys to others for profits. On the other hand, the property of large universe in ABE proposed by Lewko and Waters enlarges the practical applications by supporting flexible number of attributes. Several systems have been proposed to obtain either of the above properties. None of them achieve the two properties simultaneously in practice, which limits the commercial applications of CP-ABE to a certain extent. In this paper, we propose a practical large universe CP-ABE system supporting white-box traceability, which is suitable for commercial applications. Compared to related work, our new system provides three advantages: (1) The number of attributes is not polynomially bounded; (2) Malicious users who leak their decryption keys could be traced; (3) The storage overhead for tracing is constant. We also prove the selective security of our new system in the standard model under \"q-type\" assumption.

2014-06-19
20:11 [Job][New]

The Information Security Centre of Excellence (ISCX), University of New Brunswick, Fredericton, Canada has several openings for fully funded PhD/MS positions to work with the Centre to carry out research, design and development for the Intelligent Tools for an Automated Security Analysis and Risk Management for Large-Scale Systems project. The proposed toolset will incorporate a set of techniques for automated risk identification, security assessment (e.g., intrusion/malware detection & analysis) and mitigation planning. This project is funded under the Atlantic Innovation Foundation program. For more information about ISCX, please see www.iscx.ca.

Candidates are expected to be proficient in networking, have basic knowledge of computer security, to demonstrate interest in network security.

20:09 [Job][New]

Post-doctoral positions are available in the AriC team, on functional cryptography and/or lattice-based cryptography.

An emerging group on cryptography is looking for excellent researchers to participate to projects on functional encryption and/or lattice-based cryptography, from the algorithmic foundations to the design and implementation of advanced cryptographic primitives.

Candidates must hold (or be close to holding) a PhD thesis related to cryptology, with an emphasis on its mathematical aspects. A strong research record is expected (i.e., publications in first-tier conferences or journals).

Applications should include a CV and recommendation letters. They should be sent before July 31, 2014 but will be considered until the positions are filled. Post-doc duration is negotiable. Salary can be adjusted for senior post-docs.

20:08 [Job][New]

Post-doctoral positions are available in the AriC team, on functional cryptography and/or lattice-based cryptography.

An emerging group on cryptography is looking for excellent researchers to participate to projects on functional encryption and/or lattice-based cryptography, from the algorithmic foundations to the design and implementation of advanced cryptographic primitives.

Candidates must hold (or be close to holding) a PhD thesis related to cryptology, with an emphasis on its mathematical aspects. A strong research record is expected (i.e., publications in first-tier conferences or journals).

Applications should include a CV and recommendation letters. They should be sent before July 31, 2014 but will be considered until the positions are filled. Post-doc duration is negotiable. Salary can be adjusted for senior post-docs.

20:08 [Job][New]

The Information Security Centre of Excellence (ISCX), University of New Brunswick, Fredericton, Canada is seeking a full-time postdoctoral fellow to work with the Centre to carry out research, design and development for the Intelligent Tools for an Automated Security

Analysis and Risk Management for Large-Scale Systems project. The proposed toolset will incorporate a set of techniques for automated risk identification, security assessment and mitigation planning. Within this toolset a risk management methodology will be provided to

support a process of identifying system threats and assessing the corresponding risks. The risk management toolset will also be equipped with means to trace and analyze roots of these threats for proper selection of follow-up mitigation strategies. This project is funded under the Atlantic Innovation Foundation program. For more information about ISCX, please see www.iscx.ca.

Applicants should have a Ph.D. and expertise in one or both of following research areas:

• Information and Network Security, and network technologies and tools.

• Machine learning and data mining techniques and tools.

The following skills and experiences are very helpful:

• Development under Linux operating system

• Malware detection and analysis concepts and tools

Successful applicants will assist in one or more of following tasks:

• Developing novel learning and mining techniques for malware detection and analysis

• Develop security data-mining approaches for risk mitigation, automated understanding and predictive analytics.

• Preparing technical documents and writing and submitting the research results for publication.

The post-doc appointment is for two years and can be extended for two more year depending upon the availability of funding.

Applications will be considered until the available position is filled. To apply send your curriculum vita that in

20:07 [Job][New]

ID Quantique SA is a dynamic company specialising in quantum-safe network encryption solutions as well as hardware random number generators. Its products are used by customers in the financial and government sector worldwide. The company is based in Geneva, Switzerland.

Main Responsabilities:

•Provide internal expertise on cryptographic algorithms and protocols.

•Participation in internal as well as collaborative interdisciplinary R&D projects in the field of quantum-safe cryptography primitives, protocols and solutions.

•Implementation of cryptographic protocols.

•Monitoring of vulnerabilities and attacks relevant to the company’s products and services.

•Engagement with customers in the context of pre-sales activities.

2014-06-17
19:27 [Job][New]

The working group „Codes and Cryptography“ of the Department for Computer Science at the University of Paderborn is looking for a Research Assistant (PhD student) working in public key cryptography, more specifically in pairing based cryptography. The position also includes teaching duties.

Candidates should be proficient in complexity theory, cryptography, and number theory. A Master in Computer Science or a similar field is a condition of employment. It is expected of any candidate that a doctorate\\\'s degree will be pursued.

Applications, preferably by email, with the usual documents can be sent until June 30th, 2014.

19:26 [Job][New]

The IMDEA Software Institute (Madrid, Spain) has openings for two Ph.D. positions. We are looking for highly motivated students with a background in at least one of the following fields:

• cryptography,
• programming languages,
• verification

and an interest in carrying out research at their intersection.

The positions are within the computer-assisted cryptography group. The group is actively working on:

• the development of new programming languages and verification methods for the design and analysis of cryptographic systems,
• the implementation of computer-aided tools for cryptographic proofs, including EasyCrypt and ZooCrypt, and
• their application to the formal verification of descriptions and implementations of cryptographic standards and systems.