*19:27* [Job][New]
Research Assistant (PhD student), *University of Paderborn*
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]
Ph.D. student, *IMDEA Software Institute, Madrid*
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.

For more information about the group and our recent research, please visit: *https://www.easycrypt.info/Team*

The positions start from September 1, 2014 (negotiable); it is expected that students will complete their Ph.D. in 4 years. The salary is around 24K euros per year, which provides for very comfortable living in Madrid; in addition, students will have access to a generous health package. The working language is English.

Applications should arrive no later than July 6, 2014 and should include a CV, a cover letter, and the names and contact details for two references. Later applications will be considered until the positions are filled.

*18:17* [Pub][ePrint]
Ad-Hoc Secure Two-Party Computation on Mobile Devices using Hardware Tokens, by Daniel Demmler and Thomas Schneider and Michael Zohner
Secure two-party computation allows two mutually distrusting parties to jointly compute an arbitrary function on their private inputs without revealing anything but the result. An interesting target for deploying secure computation protocols are mobile devices as they contain a lot of sensitive user data. However, their resource restrictions make this a challenging task.In this work, we optimize and implement the secure computation protocol by Goldreich-Micali-Wigderson~(GMW) on mobile phones. To increase performance, we extend the protocol by a trusted hardware token (i.e., a smartcard). The trusted hardware token allows to pre-compute most of the workload in an initialization phase, which is executed locally on one device and can be pre-computed independently of the later communication partner. We develop and analyze a proof-of-concept implementation of generic secure two-party computation on Android smart phones making use of a microSD smartcard. Our use cases include private set intersection for finding shared contacts and private scheduling of a meeting with location preferences. For private set intersection, our token-aided implementation on mobile phones is up to two orders of magnitude faster than previous generic secure two-party computation protocols on mobile phones and even as fast as previous work on desktop computers.

*15:17* [Pub][ePrint]
Efficient Key-policy Attribute-based Encryption for General Boolean Circuits from Multilinear Maps, by Constantin Catalin Dragan and Ferucio Laurentiu Tiplea
We propose an efficient Key-policy Attribute-based Encryption (KP-ABE) scheme for general (monotone) Boolean circuits based on secret sharing and on a very particular and simple form of leveled multilinear maps,

called chained multilinear maps. The number of decryption key components is substantially reduced in comparison with the current scheme based on leveled multilinear maps, and the size of the multilinear map (in terms of bilinear map components) is less than the Boolean circuit depth, while it is quadratic in the Boolean circuit depth for the current scheme based on leveled multilinear map. Moreover, it is much easier to find chained multilinear maps than leveled multilinear maps. Selective security of the proposed schemes in the standard model is proved, under the decisional multilinear Diffie-Hellman assumption.

*15:17* [Pub][ePrint]
(Leveled) Fully Homomorphic Signatures from Lattices, by Sergey Gorbunov and Vinod Vaikuntanathan
In a homomorphic signature scheme, given a vector of signatures $\\vec{\\sigma}$ corresponding to a dataset of messages $\\vec{\\mu}$, there is a {\\it public} algorithm that allows to derive a signature $\\sigma\'$ for message $\\mu\'=f(\\vec{\\mu})$ for any function $f$. Given the tuple $(\\sigma\', \\mu\', f)$ anyone can {\\it publicly}

verify the result of the computation of function $f$.

Along with the standard notion of unforgeability

for signatures, the security of homomorphic signatures guarantees that no adversary is able to make a forgery $\\sigma^*$ for $\\mu^* \\neq f(\\vec{\\mu})$.

We construct the first homomorphic signature scheme for evaluating arbitrary functions. In our scheme, the public parameters and the size of the resulting signature grows linearly

with the depth of the circuit representation of $f$. Our scheme is secure in the standard model assuming hardness of

finding {\\it Small Integer Solutions} in hard lattices.

Furthermore, our construction has asymptotically fast verification

which immediately leads to a new solution for verifiable outsourcing with pre-processing phase. Previous state of the art constructions were limited to evaluating polynomials of constant degree, secure in random oracle model

without asymptotically fast verification.

*15:17* [Pub][ePrint]
Semi-Adaptive Attribute-Based Encryption and Improved Delegation for Boolean Formula, by Jie Chen and Hoeteck Wee
We consider *semi-adaptive* security for attribute-based encryption,where the adversary specifies the challenge attribute vector after

it sees the public parameters but before it makes any secret key

queries. We present two constructions of semi-adaptive

attribute-based encryption under static assumptions with *short*

ciphertexts. Previous constructions with short ciphertexts either

achieve the weaker notion of selective security, or require

parameterized assumptions.

As an application, we obtain improved delegation schemes for Boolean

formula with *semi-adaptive* soundness, where correctness of the

computation is guaranteed even if the client\'s input is chosen

adaptively depending on its public key. Previous delegation schemes

for formula achieve one of adaptive soundness, constant

communication complexity, or security under static assumptions; we

show how to achieve semi-adaptive soundness and the last two

simultaneously.

*15:17* [Pub][ePrint]
On a new properties of number sequences ,a randomness test and a new RC4\'s key scheduling algorithm., by Samir Bouftass and Abdelhak Azhari
In this paper, we introduce the concept of the derivative of sequence of numbers and define new statistical indices by which we discoverd new properties of randomly generated number sequences.We also build a test for pseudo random generators based on these properties and use it to confirm the weakness of RC4 key scheduling algorithm that has been reported in the litterature.

In this rescpect we publish a new RC4\'s key scheduling algorithm that don\'t have this weakness.

*12:17* [Pub][ePrint]
Single-shot security for one-time memories in the isolated qubits model, by Yi-Kai Liu
One-time memories (OTM\'s) are simple, tamper-resistant cryptographic devices, which can be used to implement sophisticated functionalities such as one-time programs. Can one construct OTM\'s whose security follows from some physical principle? This is not possible in a fully-classical world, or in a fully-quantum world, but there is evidence that OTM\'s can be built using \"isolated qubits\" -- qubits that cannot be entangled, but can be accessed using adaptive sequences of single-qubit measurements.Here we present new constructions for OTM\'s using isolated qubits, which improve on previous work in several respects: they achieve a stronger \"single-shot\" security guarantee, which is stated in terms of the (smoothed) min-entropy; they are proven secure against adversaries who can perform arbitrary local operations and classical communication (LOCC); and they are efficiently implementable.

These results use Wiesner\'s idea of conjugate coding, combined with error-correcting codes that approach the capacity of the q-ary symmetric channel, and a high-order entropic uncertainty relation, which was originally developed for cryptography in the bounded quantum storage model.