International Association for Cryptologic Research

# IACR News Central

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2015-06-02
20:30 [Event][New]

Submission: 17 December 2015
From April 13 to April 15
Location: Fes, Morocco

09:17 [Pub][ePrint]

Digital signature is a fundamental primitive with numerous applications. Following the development of pairing-based cryptography, several taking advantage of this setting have been proposed. Among them, the Camenisch-Lysyanskaya (CL) signature scheme is one of the most flexible and has been used as a building block for many other protocols. Unfortunately, this scheme suffers from a linear size in the number of messages to be signed which limits its use in many situations.

In this paper, we propose a new signature scheme with the same features as CL-signatures but without the linear-size drawback: our signature consists of only two elements, whatever the message length, and our algorithms are more efficient. This construction takes advantage of using type 3 pairings, that are already widely used for security and efficiency reasons.

We prove the security of our scheme without random oracles but in the generic group model. Finally, we show that protocols using CL-signatures can easily be instantiated with ours, leading to much more efficient constructions.

09:17 [Pub][ePrint]

We propose new generic key recovery attacks on Feistel-type block ciphers. The

proposed attack is based on the all subkeys recovery approach presented in SAC 2012, which

determines all subkeys instead of the master key. This enables us to construct a key recovery

attack without taking into account a key scheduling function. With our advanced techniques,

we apply several key recovery attacks to Feistel-type block ciphers. For instance, we show

8-, 9- and 11-round key recovery attacks on n-bit Feistel ciphers with 2n-bit key employing

random keyed F-functions, random F-functions, and SP-type F-functions, respectively.

Moreover, thanks to the meet-in-the-middle approach, our attack leads to low-data complexity.

To demonstrate the usefulness of our approach, we show a key recovery attack on the

8-round reduced CAST-128, which is the best attack with respect to the number of attacked

rounds. Since our approach derives the lower bounds on the numbers of rounds to be secure

under the single secret key setting, it can be considered that we unveil the limitation of

designing an efficient block cipher by a Feistel scheme such as a low-latency cipher.

09:17 [Pub][ePrint]

Profiled side-channel attacks are understood to be powerful when applicable: in the best case when an adversary can comprehensively characterise the leakage, the resulting model leads to attacks requiring a minimal number of leakage traces for success. Such complete\' leakage models are designed to capture the scale, location and shape of the profiling traces, so that any deviation between these and the attack traces potentially produces a mismatch which renders the model unfit for purpose. This severely limits the applicability of profiled attacks in practice and so poses an interesting research challenge: how can we design profiled distinguishers that can tolerate (some) differences between profiling and attack traces?

This submission is the first to tackle the problem head on: we propose distinguishers (utilising unsupervised machine learning methods, but also a down-to-earth\' method combining mean traces and PCA) and evaluate their behaviour across an extensive set of distortions that we apply to representative trace data. Our results show that the profiled distinguishers are effective and robust to distortions to a surprising extent.

06:17 [Pub][ePrint]

Securely sharing the same secret key among multiple parties

is the main concern in symmetric cryptography that is the workhorse

of modern cryptography due to its simplicity and fast speed. Typically asymmetric cryptography is used to set up a shared secret between parties, after which the switch to symmetric cryptography can be made. In this paper, we introduce a novel key exchange protocol based on physical hardware implementation to establish a shared secret between parties rather than relying on mathematical implementation of asymmetric cryptography. In particular, the key exchange is dependent on a new security concept named as virtual proof of reality or simply virtual proof (VP) that enables proof of a physical statement over untrusted digital communication channels between two parties (a prover and a verifier) residing in two separate local systems. We firstly exploit the VP to secure key exchange and further prove it by using experimental data. The key transferred in this protocol is only seen by the prover and hidden from not only the adversary but also the verifier. While only the verifier can successfully discover it.

05:07 [Job][New]

The Computer Science department at the University of Auckland seeks 2 Ph.D. Students to join the cloud security team led by Dr. Giovanni Russello.

This research will take place in a new MBIE-funded Cyber Security STRATUS (Security Technologies Returning Accountability, Transparency and User-centric Services to the Cloud) project and will be in collaboration with University of Waikato, UniTech, the Cloud Security Alliance, and several New Zealand-based industrial partners (https://stratus.org.nz). The aim is to research novel yet practical cloud security tools to be adopted by the industry partners.

The research conducted by the University of Auckland’s team will focus on applied cryptography for retrieval and processing of encrypted data in outsourced and untrusted environments. This involves a substantial program of research to develop, implement and apply to industrial case studies.

Applicants are required to have completed (or be close to completing) a Master degree (or equivalent) with outstanding grades in Computer Science, Mathematics, or closely related areas. Additional knowledge in related disciplines such as, e.g., complexity theory or IT security is welcome.

The candidate should be able not only to design but also implement working prototypes of the crypto scheme developed during the research period.

The STRATUS project will provide a stipend of 25,000 NZD p.a. and cover the costs of the tuition fee for 3 years.

05:07 [Job][New]

The Computer Science department at the University of Auckland seeks a Research Fellow/Postdoctoral Researcher to join the cloud security team led by Dr. Giovanni Russello.

This research will take place in a new MBIE-funded Cyber Security STRATUS (Security Technologies Returning Accountability, Transparency and User-centric Services to the Cloud) project and will be in collaboration with University of Waikato, UniTech, the Cloud Security Alliance, and several New Zealand-based industrial partners (https://stratus.org.nz). The aim is to research novel yet practical cloud security tools to be adopted by the industry partners.

The research conducted by the University of Auckland’s team will focus on applied cryptography for retrieval and processing of encrypted data in outsourced and untrusted environments. This involves a substantial program of research to develop, implement and apply to industrial case studies.

This is a full time post for a fixed-term of 2 years. Salary starts at 74000 NZD per annum.

Applicants should have a Ph.D. in computer science in a relevant field (cloud security with emphasis on crypto solutions) a demonstrable research interest in the area of applied crypto with emphasis in homomorphic encryption for encrypted data processing and retrieval focusing on cloud computing, and experience in designing, analysing, and efficiently implement novel crypto algorithms. Previous experience in the area of big data with emphasis on privacy/confidentiality would be advantageous.

2015-06-01
16:05 [Event][New]

Submission: 10 August 2015
From November 1 to November 3
Location: Beijing, China

2015-05-31
21:17 [Pub][ePrint]

In this paper, we present a single round two-party attribute-based authenticated key exchange protocol. Since pairing is a costly operation and the composite order groups must be very large to ensure security, we focus on pairing free protocols in prime order groups. We propose a new protocol that is pairing free, working in prime order group and having tight reduction to Strong Diffie Hellman (SDH) problem under the Attribute-based CK model which is a natural extension of the CK model for the public key setting. Our proposed attribute based authenticated key exchange protocol (ABAKE) also does not depend on any underlying attribute based encryption schemes unlike the previous solutions for ABAKE. Ours is the first scheme that removes this restriction. Thus, the first major advantage is that smaller key sizes are sufficient to achieve comparable security. Our scheme has several other advantages. The major one being the capability to handle active adversaries. Most of the previous Attribute-Based authenticated key exchange protocols can offer security only under passive adversaries. Our protocol recognizes the corruption by an active adversary and aborts the process. In addition to this property, our scheme satisfies other security properties that are not covered by CK model such as forward secrecy, key compromise impersonation attacks and ephemeral key compromise impersonation attacks.

21:17 [Pub][ePrint]

We present a new, decentralized, efficient, and secure digital cryptocurrency, in which the ordinary users themselves keep turns to ensure that the systems works well.

21:17 [Pub][ePrint]

We give a simple heuristic sieving algorithm for the $m$-dimensional

exact shortest vector problem

(SVP) which runs in time $2^{0.3112m +o(m)}$. Unlike previous time-memory

trade-offs, we do not increase the memory, which stays at its bare minimum

$2^{0.2075m +o(m)}$. To achieve this complexity, we borrow a recent tool

from coding theory, known as nearest neighbor search for binary code

words. We simplify its analysis, and show that it can be adapted to solve

this variant of the fixed-radius nearest neighbor search problem:

Given a list of exponentially many unit vectors of $\\mR^m$, and an

angle $\\gamma\\pi$, find all pairs of

vectors whose angle $\\leq\\gamma\\pi$. The complexity is sub-quadratic which leads to the improvement for lattice sieves.