International Association for Cryptologic Research

# IACR News Central

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Further sources to find out about changes are CryptoDB, ePrint RSS, ePrint Web, Event calender (iCal).

2014-10-20
15:17 [Pub][ePrint]

A non-malleable code protects messages against various classes of tampering.

Informally, a code is non-malleable if the effect of applying any tampering

function on an encoded message is to either retain the message or to replace

it with an unrelated message.

Two main challenges in this area -- apart from establishing

the feasibility against different families of tampering -- are to obtain

{\\em explicit constructions} and to obtain {\\em high-rates} for such

constructions.

In this work, we present a compiler to transform low-rate (in fact, zero

rate) non-malleable codes against certain class of tampering into an

optimal-rate -- i.e., rate 1 -- non-malleable codes against the same class.

If the original code is explicit, so is the new one.

When applied to the family of bit-wise tampering functions, this subsumes

(and greatly simplifies) a recent result of Cheraghchi and Guruswami (TCC

2014). Further, our compiler can be applied to non-malleable codes against

the class of bit-wise tampering and bit-level permutations. Combined with

the rate-0 construction in a companion work, this yields the first explicit

rate-1 non-malleable code for this family of tampering functions.

Our compiler uses a new technique for boot-strapping non-malleability by

introducing errors, that may be of independent interest.

15:17 [Pub][ePrint]

In this paper we revisit the modular inversion hidden number problem and the inversive congruential pseudo random number generator and consider how to more efficiently attack them in terms of fewer samples or outputs. We reduce the attacking problem to finding small solutions of systems of modular polynomial equations of the form $a_i+b_ix_0+c_ix_i+x_0x_i=0 (\\mod p)$, and present two strategies to construct lattices in Coppersmith\'s lattice-based root-finding technique for the solving of the equations. Different from the choosing of the polynomials used for constructing lattices in previous methods, a part of polynomials chosen in our strategies are linear combinations of some polynomials generated in advance and this enables us to achieve a larger upper bound for the desired root. Applying the solving of the above equations to analyze the modular inversion hidden number problem, we put forward an explicit result of Boneh et al. which was the best result so far, and give a further improvement in the involved lattice construction in the sense of requiring fewer samples. Our strategies also give a method of attacking the inversive congruential pseudo random number generator, and the corresponding result is the best up to now.

12:17 [Pub][ePrint]

In this work, we first formalize the notion of dynamic group signatures with distributed traceability, where the capability to trace signatures is distributed among $n$ managers without requiring any interaction. This ensures that only the participation of all tracing managers permits tracing a signature, which reduces the trust placed in a single tracing manager. The threshold variant follows easily from our definitions and constructions. Our model offers strong security requirements.

Our second contribution is a generic construction for the notion which has a concurrent join protocol, meets strong security requirements, and offers efficient traceability, i.e.\\ without requiring tracing managers to produce expensive zero-knowledge proofs for tracing correctness. To dispense with the expensive zero-knowledge proofs required in the tracing, we deploy a distributed tag-based encryption with public verifiability.

Finally, we provide some concrete instantiations, which, to the best of our knowledge, are the first efficient provably secure realizations in the standard model simultaneously offering all the aforementioned properties. To realize our constructions efficiently, we construct an efficient distributed (and threshold) tag-based encryption scheme that works in the efficient Type-III asymmetric bilinear groups. Our distributed tag-based encryption scheme yields short ciphertexts (only 1280 bits at 128-bit security), and is secure under an existing variant of the standard decisional linear assumption.

Our tag-based encryption scheme is of independent interest and is useful for many applications beyond the scope of this paper. As a special case of our distributed tag-based encryption scheme, we get an efficient tag-based encryption scheme in Type-III asymmetric bilinear groups that is secure in the standard model.

2014-10-19
17:13 [Event][New]

Submission: 27 October 2014
Notification: 27 November 2014
From January 19 to January 19
Location: Amsterdam, The Netherlands

2014-10-16
18:17 [Pub][ePrint]

Currently, the Internet Research Task Force (IRTF) discusses requirements for new elliptic curves to be standardized in TLS and other internet protocols. This position paper discusses the view of the members of the ECC Brainpool on these requirements, in particular with respect to hardware implementations.

16:50 [Job][New]

Following recent advances in high throughput sequencing, it can be expected that, in the near future, more and more individuals will have their whole genome extracted, stored and analyzed in a routine fashion. Although this perspective is full of promises in terms of personalized preventive and curative medicine as well as medical research, it should also be acknowledged that the genome of an individual is in essence extremely sensitive data from (at least) a privacy standpoint. Thus, for such personalized medicine-oriented platforms to reliably exist, it is necessary to develop specific counter-measures providing intrinsic protection of the genomic data when manipulated by an IT infrastructure.

In this context, a very promising approach is grounded in homomorphic encryption as a means of computing directly over encrypted data.

The purpose of the present postdoctoral offer is thus to investigate the practical relevance of using homomorphic encryption techniques for privacy-preserving genetic data processing. The main use case will consist in performing requests on a database of genomes represented by their variants. Several scenarios will be investigated in particular with respect to the privacy of the request itself on top of the privacy of the genetic data. In this various scenarios, the candidate is expected to identify the most suitable homomorphic encryption techniques ranging from additive-only (e.g. suitable for private requests on unencrypted data) and multiplicative-only (e.g. suitable for disjunctive public requests on encrypted genetic data) homomorphic encryption systems to the use of the more recent (and more costly) fully homomorphic encryption techniques. The candidate will also be expected to build prototypes for one or more of the above scenarios in order to experimentally demonstrate the practical viability of the solutions, in particular with respect to performances.

16:02 [News]

In response to recent discoveries of protocol vulnerabilities and in sync with major browser producers, the IACR web server no longer supports SSLv2 and SSLv3. If you face difficulties accessing the IACR services over an encrypted connection, please contact webmaster(at)iacr.org.

03:18 [Event][New]

Submission: 2 March 2015
Notification: 18 May 2015
From September 13 to September 16
Location: Saint Malo, France

2014-10-15
17:44 [Election]

## IACR 2014 Election

The 2014 election is being held to fill three of nine IACR Director positions.

### Vote Now!

The 2014 Election for Directors of the IACR Board is now open. Eligible IACR members may vote now through November 15th using the Helios cryptographically-verifiable election system. You may vote as often as you wish, but only your last vote will be counted.

Eligible members of the IACR (generally people who attended an IACR conference or workshop in 2013) should have received voting credentials from system@heliosvoting.org, sent to their email address of record with the IACR. Questions about this election may be sent to elections@iacr.org.

More information about the candidates can be found at the IACR elections page.

### Election Committee

• Bart Preneel (Chair)
• Michel Abdalla (Returning Officer)
• Anna Lysyanskaya

2014-10-14
20:00 [Event][New]

Submission: 14 November 2014
Notification: 8 February 2015
From May 18 to May 20
Location: Oakland, USA