International Association for Cryptologic Research

# IACR News Central

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2015-06-14
21:17 [Pub][ePrint]

In [Eurocrypt 2004] Katz and Ostrovsky establish the exact round complexity of secure two-party computation with respect to black-box proofs of security. They prove that 5 rounds are necessary for secure two-party protocols (4-round are sufficient if only one party receives the output) and provide a protocol that matches such lower bound. The main challenge when designing such protocol is to parallelize the proofs of consistency provided by both parties - necessary when security against malicious adversaries is considered- in 4 rounds. Toward this goal they employ specific proofs in which the statement can be unspecified till the last round but that require non-black-box access to the underlying primitives.

A rich line of work [IKLP06, Hai08, CDSMW09, IKOS07, PW09] has shown that the non- black-box use of the cryptographic primitive in secure two-party computation is not necessary by providing black-box constructions matching basically all the feasibility results that were previously demonstrated only via non-black-box protocols.

All such constructions however are far from being round optimal. The reason is that they are based on cut-and-choose mechanisms where one party can safely take an action only after the other party has successfully completed the cut-and-choose phase, therefore requiring additional rounds.

A natural question is whether round-optimal constructions do inherently require non-black- box access to the primitives, and whether the lower bound shown by Katz and Ostrovsky can only be matched by a non-black-box protocol.

In this work we show that round-optimality is achievable even with only black-box access to the primitives. We provide the first 4-round black-box oblivious transfer based on any enhanced trapdoor permutation. Plugging a parallel version of our oblivious transfer into the black- box non-interactive secure computation protocol of [IKO+11] we obtain the first round-optimal black-box two-party protocol in the plain model for any functionality.

2015-06-13
17:11 [News]

The IACR has recently started sponsoring select Cryptology Schools. If you would like to propose an IACR-sponsored school that takes place on/before February 2016, then your last chance to submit proposals is June 30. The next round of proposals is not until December 31. More information about the application process can be found at http://www.iacr.org/schools/.

2015-06-12
21:17 [Pub][ePrint]

Fully homomorphic encryption is an encryption method with the property that any computation on the plaintext can be performed by a party having access to the ciphertext only.

Here, we formally define and give schemes for \\emph{quantum} homomorphic encryption, which is the encryption of \\emph{quantum} information such that \\emph{quantum} computations can be performed given the ciphertext only. Our schemes allow for arbitrary Clifford group gates, but become inefficient for circuits with

large complexity, measured in terms of the non-Clifford portion of the circuit (we use the $\\pi/8$\'\' non-Clifford group gate, also known as the $T$-gate).

More specifically, two schemes are proposed: the first scheme has a decryption procedure whose complexity scales with the square of the \\emph{number} of $T$-gates (compared with a trivial scheme in which the complexity scales with the total number of gates); the second scheme

uses a quantum evaluation key of length given by a polynomial of degree exponential in the circuit\'s

$T$-gate depth, yielding a homomorphic scheme for quantum circuits with constant $T$-depth. Both schemes build on a classical fully homomorphic encryption scheme.

A further contribution of ours is to formally define the security of encryption schemes for quantum messages: we define \\emph{quantum indistinguishability under chosen plaintext attacks} in both the public- and private-key settings. In this context, we show the equivalence of several definitions.

Our schemes are the first of their kind that are secure under modern cryptographic definitions, and can be seen as a quantum analogue of classical results establishing homomorphic encryption for circuits with a limited number of \\emph{multiplication} gates. Historically, such results appeared as precursors to the breakthrough result establishing classical fully homomorphic encryption.

04:08 [Event][New]

Submission: 30 June 2015
Notification: 20 July 2015
From September 8 to September 8
Location: Tokyo, Japan

2015-06-11
21:17 [Forum]

From: 2015-11-06 21:11:12 (UTC)

17:37 [Event][New]

From June 30 to July 2
Location: PHILADELPHIA, United States

15:16 [Job][New]

Two 0.5 full-time equivalent (FTE) positions are offered as part of the DFG funded project Algebraic Fault Attacks.

These positions are remunerated pro rata at salary band E13 of the German public-sector wage agreement (TV-L E13). Candidates may combine these positions with one 0.25 FTE teaching assistantship each.

The successful candidates will participate in an area of the project which uses Computer Algebra techniques and their integration with SAT solvers to break cryptographic hardware primitives based on the information obtained from fault attacks. The interdisciplinary, state-of-the-art approach requires rigorous and broad-based mathematical knowledge and an openness towards computer science methods.

Detailed job requirements are listed in the link below.

06:37 [Job][New]

The Ruhr University Bochum is offering a 2-year post-doc position in theoretical cryptography, working on the ERC project \"Efficient Resource Constrained Cryptography\". Required is a PhD in cryptography and excellence in research, proven for example by publications in IACR conferences and workshops.

Applicants interested in the positions should provide the following information in pdf format with the application:

- Motivation letter

- CV

- List of publications, mark your top 2

This position will be filled as soon as possible, late applications will be considered.

06:37 [Job][New]

The researcher will work on a project entitled “Securing emerging network technologies with homomorphic encryption”. The overall aim of the project is to design methods for secure processing of network data in emerging networks using practical variants of homomorphic encryption. Recent advances in cryptography will be applied to secure the virtualization of the ICT infrastructure (such as “cloud” processing and storage) and new flexible networking technologies such as software defined networks (SDN) and network function virtualization (NFV). Work tasks will include: analysis of suitable network functions for homomorphic processing; analysis of practical homomorphic encryption algorithms; secure protocol design and analysis; and experimental implementations.

2015-06-10
14:44 [Event][New]

Submission: 7 September 2015
Notification: 12 November 2015
From February 29 to March 4
Location: San Francisco, USA