*06:25* [Job][New]
Research + Teaching Assistant / Ph.D. student, *University of Applied Sciences Offenburg, Germany*
The Department of Media and Information Technology is looking for a research and research assistant in the field of applied cryptography. The possibility to earn a PhD degree in cooperation with the University of Mannheim is given. **Job description:**

- Active and self-reliant participation in research projects in the area of applied cryptography, e.g. on topics in light-weight cryptography or in analysis of cryptographic protocols and interfaces.
- Assisting in computer science teaching (in particular tutoring).
- Administration of the IT security lab (computer pool).

**Requirements**

- Master degree or equivalent in mathematics, computer science, or similar.
- Very good skills in mathematics (in particular algebra and combinatorics) and computer science (in particular programming and algorithmics).
- First experience in cryptography and IT security.
- Basic knowledge in system administration (Linux, Windows).
- Fluent English (both spoken and written).

The position is initially for two years, with possibility for extension upon successful progress in the PhD studies.

*06:15* [PhD][New]
Edoardo Persichetti: Improving the Efficiency of Code-Based Cryptography
Name: Edoardo Persichetti

Topic: Improving the Efficiency of Code-Based Cryptography

Category: public-key cryptography

Description: Recent public-key cryptography is largely based on number theory problems, such as factoring or computing of discrete logarithm. These systems constitute an excellent choice in many applications, and their security is well defined and understood. One of the major drawbacks, though, is that they will be vulnerable once quantum computers of an appropriate size are available. There is then a strong need for alternative systems that would resist attackers equipped with quantum technology.

\r\n\r\nOne of the most well-known systems of this kind is the McEliece cryptosystem, introduced in 1978, that is based on algebraic coding theory. There are no known vulnerabilities against quantum computers, and it has a very fast and efficient encryption procedure. However, it has also one big flaw, the size of the public key, that makes it impractical for many applications.

\r\n\r\nThe first part of this thesis is dedicated to finding a way to significantly reduce the size of the public key.\r\nLatest publications achieve very good results by using codes with particular structures, obtaining keys as small as 4,096 bits. Unfortunately, almost all of the variants presented until now have been broken or proven to be insecure against the so-called *structural attacks*, i.e. attacks that aim to exploit the hidden structure in order to recover the private key. \r\nMy work is based on Generalized Srivastava codes and represents a generalization of the Quasi-Dyadic scheme proposed by Misoczki and Barreto, with two advantages: a better flexibility, and improved resistance to all the known attacks. An efficient implementation of the above scheme is also provided, as a result of a joint work with P.-L. Cayrel and G. Hoffmann.

\r\n\r\nIn the next chapters, other important aspects of code-based cryptography are investigated. These include the study of a higher security standard, called indistinguishability under a chosen ciphertext attack, in the standard model, and th[...]

*22:17* [Pub][ePrint]
Shielding circuits with groups, by Eric Miles and Emanuele Viola
We show how to efficiently compile any given circuit C into a leakage-resistant circuit C\' such that any function on the wires of C\' that leaks information during a computation C\'(x) yields advantage in computing the product of |C\'|^{Omega(1)} elements of the alternating group A_u. In combination with new compression bounds for A_u products, also obtained here, C\' withstands leakage from virtually any class of functions against which average-case lower bounds are known. This includes communication protocols, and AC^0 circuits augmented with few arbitrary symmetric gates. If NC^1 \\neq TC^0 then then the construction resists TC^0 leakage as well. In addition, we extend the construction to the multi-query setting by relying on a simple secure hardware component.We build on Barrington\'s theorem [JCSS \'89] and on the previous leakage-resistant constructions by Ishai et al. [Crypto \'03] and Faust et al. [Eurocrypt \'10]. Our construction exploits properties of A_u beyond what is sufficient for Barrington\'s theorem.

*22:17* [Pub][ePrint]
Generalized (Identity-Based) Hash Proof System and Its Applications , by Yu Chen and Zongyang Zhang and Dongdai Lin and Zhenfu Cao
In this work, we generalize the paradigm of hash proof system (HPS) proposed by Cramer and Shoup~\\cite{CS2002}. In the central of our generalization, we lift subset membership problem to distribution distinguish problem.

Our generalized HPS clarifies and encompass all the known public-key encryption (PKE) schemes

that essentially implement the idea of hash proof system.

Moreover, besides existing smoothness property, we introduce an additional property named anonymity for HPS.

As a natural application, we consider anonymity for PKE in the presence of key-leakage,

and provide a generic construction of leakage-resilient anonymous PKE from anonymous HPS.

We then extend our generalization to the identity-based setting.

Concretely, we generalize the paradigm of identity-based hash proof system (IB-HPS)

proposed by Boneh~\\textit{et al.}~\\cite{BGH2007} and Alwen~\\textit{et al.}~\\cite{Alwen2010},

and introduce anonymity for it. As an interesting application of anonymous IB-HPS,

we consider security for public-key encryption with keyword search (PEKS) in the presence of token-leakage,

and provide a generic construction of leakage-resilient secure PEKS from leakage-resilient anonymous IBE,

which in turn is based on anonymous IB-HPS.

*16:17* [Pub][ePrint]
Defensive Leakage Camouflage, by E. Brier and Q. Fortier and R. Korkikian and K. W. Magld and D. Naccache and G. Ozari de Almeida and A. Pommellet and A. H. Ragab and J. Vuillemin
This paper considers the transfer of digital data over {\\sl leaky and noisy} communication channels. We develop defensive strategies exploiting the fact that noise prevents the attacker from accurately measuring leakage.The defense strategy described in this paper pairs each useful data element $k$ with a camouflage value $v$ and simultaneously transmits both $k$ and $v$ over the channel. This releases an emission $e(k,v)$. We wish to select the camouflage values $v(k)$ as a function of $k$ in a way that makes the quantities $e(k,v(k))$ as {\\sl indistinguishable} as possible from each other.

We model the problem and show that optimal camouflage values can be computed from side-channels under very weak physical assumptions. The proposed technique is hence applicable to a wide range of readily available technologies.

We propose algorithms for computing optimal camouflage values when the number of samples per trace is moderate (typically $\\leq 6$) and justify our models by a statistical analysis.

We also provide experimental results obtained using FPGAs.