International Association for Cryptologic Research

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2015-05-18
09:17 [Pub][ePrint]

We present the oblivious machine, a concrete notion for multiparty

random access machine (RAM) computation and a toolchain to allow the

efficient execution of general programs written in a subset of C that

allows RAM-model computation over integers. The machine only leaks the

list of possible instructions and the running time. Our work is based

on the oblivious array for secret-sharing-based multiparty computation

by Keller and Scholl (Asiacrypt 14). This means that we only incur a

polylogarithmic overhead over the execution on a normal CPU.

We implemented our construction using the clang compiler from the LLVM

project and the SPDZ protocol by Damgård et al. (Crypto 12). The

latter provides active security against a dishonest majority and works

in the preprocessing model. The online phase clock rate of the

resulting machine is 41 Hz for a memory size of 1024 64-bit integers

and 2.2 Hz for a memory of 2^20 integers. Both timings have been taken

for two parties in a local network.

To further showcase our toolchain, we implemented and benchmarked

private regular expression matching. Matching a string of length 1024

against a regular expression with 69270 transitions as a finite state

machine takes seven hours online time, of which more than six hours

09:17 [Pub][ePrint]

We present a new fully homomorphic encryption (FHE) scheme that is efficient for practical applications. The main feature of our scheme is that noise reduction considered essential in current FHE schemes, such as boot strapping and modulus switching, is not needed in our scheme, because it allows arbitrarily large noises in its ciphertexts.

A ciphertext in our scheme is a vector with its dimension specified as a security parameter of the encryption key. The dimension of ciphertexts does not change with homomorphic operations and all ciphertext elements are in a finite domain, so our scheme is compact. In addition, our scheme can directly encrypt big integers, rather than only bit messages.

We proved the hardness of recovering encryption keys from any number of ciphertexts with chosen plaintexts and then the semantic security of our scheme. The hardness of recovering keys from ciphertexts is based on the approximate greatest common divisors problem.

We implemented a prototype of our scheme and evaluated its concrete performance extensively from the aspects of encryption, decryption, homomorphic operations,

and bitwise operators over ciphertexts.

The efficiency of our scheme is confirmed by the evaluation result.

2015-05-17
09:17 [Pub][ePrint]

Besides attracting a billion dollar economy, Bitcoin revolutionized the field of digital currencies and influenced many adjacent areas. This also induced significant scientific interest. In this survey, we unroll and structure the manyfold results and research directions. We start by introducing the Bitcoin protocol and its building blocks. From there we continue to explore the design space by discussing existing contributions and results. In the process, we deduce the fundamental structures and insights at the core of the Bitcoin protocol and its applications. As we show and discuss, many key ideas are likewise applicable in various other fields, so that their impact reaches far beyond Bitcoin itself.

09:17 [Pub][ePrint]

Advanced modern processors support Single Instruction Multiple Data (SIMD) instructions (e.g. Intel-AVX, ARM-NEON) and a massive body of

research on vector-parallel implementations of modular arithmetic, which are crucial components for modern public-key cryptography ranging from RSA, ElGamal, DSA and ECC, have been conducted.

In this paper, we introduce a novel Double Operand Scanning (DOS) method to speed-up multi-precision squaring with non-redundant representations on SIMD architecture.

The DOS technique partly doubles the operands and computes the squaring operation without Read-After-Write (RAW) dependencies between source and destination variables.

Furthermore, we presented Karatsuba Cascade Operand Scanning (KCOS) multiplication and Karatsuba Double Operand Scanning (KDOS) squaring by adopting additive and subtractive Karatsuba\'s methods, respectively.

The proposed multiplication and squaring methods are compatible with separated Montgomery algorithms and these are highly efficient for RSA crypto system.

Finally, our proposed multiplication/squaring, separated Montgomery multiplication/squaring and RSA encryption outperform the best-known results by 22/41\\%, 25/33\\% and 30\\% on the Cortex-A15 platform.

09:17 [Pub][ePrint]

Fully homomorphic encryption (FHE) has important applications in cloud computing. However, almost all fully homomorphic encryption schemes share two common flaws that they all use large-scale secret keys and some operations inefficient. In this paper, the \"special b\" variant of the Learning With Errors problem (bLWE) is presented, and helps us construct the first circularly secure key switching process which can replace the key switching process and similar re-linearization process used by the existing FHE schemes. Then, we present an efficient FHE. Compared with Brakerski\'s scheme, our scheme reduces L secret keys to one and is more efficient. Finally, we prove the chosen-plaintext attack (CPA) security of the fully homomorphic scheme and the circular security of key switching process in standard model under the learning with errors problem (LWE) assumption.

2015-05-15
16:28 [Event][New]

Submission: 31 May 2015
From September 17 to September 17
Location: Saint-Malo, France

09:17 [Pub][ePrint]

In this work we focus on tailoring and optimizing the computational Private Information Retrieval (cPIR) scheme proposed in WAHC 2014 for efficient execution on graphics processing units (GPUs). Exploiting the mass parallelism in GPUs is a commonly used approach in speeding up cPIRs. Our goal is to eliminate the efficiency bottleneck of

the Dor\\\"{o}z et al construction which would allow us to take advantage of its excellent bandwidth performance. To this end, we develop custom code to support polynomial ring operations and extend them to realize the evaluation functions in an optimized manner on high end GPUs. Specifically, we develop optimized CUDA code to support large degree/large

coefficient polynomial arithmetic operations such as modular multiplication/reduction, and modulus switching. Moreover, we choose same prime numbers for both the CRT domain representation of the polynomials and for the modulus switching implementation of the somewhat homomorphic encryption scheme. This allows us to combine two arithmetic domains, which reduces the number of domain conversions and permits us to perform faster arithmetic. Our implementation achieves 14-34 times speedup for index comparison and 4-18 times speedup for data aggregation compared to a pure CPU software implementation.

tion compared to a pure CPU software implementation.

09:17 [Pub][ePrint]

Garg, Gentry and Halevi (GGH) described the first candidate multilinear maps using ideal lattices. However, Hu and Jia presented an efficient attack on GGH map, which breaks two applications of multipartite key exchange (MPKE) and witness encryption (WE) based on the hardness of 3-exact cover problem by using GGH. We describe a new construction of multilinear map using random matrix, which supports the applications for public tools of encoding in the origin GGH, such as MPKE and WE. The security of our construction depends upon new hardness assumption. Furthermore, our construction removes the special structure of the ring element in the principal ideal lattice problem, and avoids potential attacks generated by algorithm of solving short principal ideal lattice generator.

2015-05-14
17:16 [Job][New]

Apcera is disrupting the world of IT with the world’s first OS for the Hybrid Cloud. Our Hybrid Cloud OS has policy and governance built in at the core, allowing IT organizations and developers alike to safely and easily develop, deploy, orchestrate and govern any imaginable workload — apps, services, Docker containers, OS’s — either on premise or in any cloud, public or private, in a friction-free and trusted fashion.

Based in SOMA in SF and led by CEO Derek Collison, Apcera has substantial backing from Ericsson, the global technology, cloud and mobile giant headquartered in Sweden. Join us and help build the world\'s first Hybrid Cloud OS.

As a Security Architect at Apcera, you will oversee the security protocols in use inside and outside the Continuum platform, inform choices for security technologies and policies and review code for secure practices and patterns. You will lead efforts to infiltrate Apcera’s security controls, you will work within the Go community, the open source cryptographic community and with security leaders in the industry to improve and harden the Continuum platform.

QUALIFICATIONS:

Bachelor’s degree in Computer Science or equivalent experience with security technologies

Minimum of 7 years software development experience in a combination of any of the following languages: GO, C, C++, Java, C#, Python or Ruby

Minimum of 5 years’ experience working with Linux operating system development

Minimum 2 years in security engineering, crypto, policy, auth or related technologies

Understanding of the basic underpinnings of cryptographic technologies, authentication, authorization and distributed trust

Understanding about how Kerberos authentication works

Experience with techniques for escalating privilege

Knowledge about how basic cryptographic technologies relate to the design of OpenPGP and X.509 PKIX

In-depth knowledge of security

17:15 [Job][New]

POSITION OF LECTURER IN THE DEPARTMENT OF MATHEMATICS AND APPLIED MATHEMATICS (CLOSING DATE 5 JUNE 2015)

The Department of Mathematics and Applied Mathematics at the University of Cape Town is a large and dynamic establishment with over thirty faculty members. We seek to make one new appointment in Mathematics or Applied Mathematics at the level of Lecturer. Applications in all areas of Mathematics and Applied Mathematics will be considered.

Requirements include: A PhD in the mathematical sciences. (Scientific publications, postdoc, teaching experience and student supervision are all advantageous.)

Responsibilities include: Teaching and developing undergraduate as well as postgraduate courses in mathematics (within and beyond the science faculty). Developing and pursuing an active research program, which includes student supervision. Course convening, departmental and faculty administrative duties.

The annual remuneration package for 2015, including benefits: R528 275.

To apply, please e-mail the below documents in a single pdf file to Ms Edith Graham at recruitment04 (at) uct.ac.za:

- Full Curriculum Vitae (CV)

- A clearly articulated statement describing their teaching experience and philosophy (applies to both positions), and a research statement (applies to standard academic position)

Please ensure the title and reference number are indicated in the subject line.

An application which does not comply with the above requirements will be regarded as incomplete.

You can also write to Dr Christine Swart at christine.swart (at) uct.ac.za for more information on the department.

Telephone: +27 21 650 5405

Website: http://www.mth.uct.ac.za

Reference number: E15074

Closing date: 05 June 2015

15:17 [Pub][ePrint]

In 2004, Canetti-Halevi-Katz and later Boneh-Katz showed generic CCA-secure PKE constructions from a CPA-secure IBE. Goyal et al. in 2006 further extended the aforementioned idea implicitly to provide a specific CCA-secure KP-ABE with policies represented by monotone access trees. Later, Yamada et al. in 2011 generalized the CPA to CCA conversion to all those ABE, where the policies are represented by either monotone access trees (MAT) or monotone span programs (MSP), but not the others like sets of minimal sets. Moreover, the underlying CPA-secure constructions must satisfy one of the two features called {\\em key-delegation} and {\\em verifiability}. Along with ABE, many other different encryptions schemes, such as inner-product, hidden vector, spatial encryption schemes etc. can be studied under an unified framework, called {\\em functional encryption} (FE), as introduced by Boneh-Sahai-Waters in 2011. The generic conversions, due to Yamada et al., can not be applied to all these functional encryption schemes. On the other hand, to the best of our knowledge, there is no known CCA-secure construction beyond ABE over MSP and MAT. This paper provides different ways of obtaining CCA-secure functional encryptions of almost all categories. In particular, we provide {\\bf a generic conversion from a CPA-secure functional encryption into a CCA-secure functional encryption} provided the underlying CPA-secure encryption scheme has either restricted delegation or verifiability feature. We observe that almost all functional encryption schemes have this feature. The KP-FE schemes of Waters (proposed in 2012) and Attrapadung (proposed in 2014) for regular languages do not possess the usual delegation property. However, they can be converted into corresponding CCA-secure schemes as they satisfy the {\\em restricted delegation}.