*18:17* [Pub][ePrint]
Secret-Sharing for NP from Indistinguishability Obfuscation, by Ilan Komargodski and Moni Naor and Eylon Yogev
A computational secret-sharing scheme is a method that enables a dealer, that has a secret, to distribute this secret among a set of parties such that a \"qualified\" subset of parties can reconstruct the secret while any \"unqualified\" subset of parties cannot efficiently learn anything about the secret. The collection of \"qualified\" subsets is defined by a monotone Boolean function.It has been a major open problem to understand which (monotone) functions can be realized by a computational secret-sharing schemes. Yao suggested a method for secret-sharing for any function that has a polynomial-size monotone circuit (a class which is strictly smaller than the class of monotone functions in P). Around 1990 Rudich raised the possibility of obtaining secret-sharing for all monotone functions in NP: In order to reconstruct the secret a set of parties must be \"qualified\" and provide a witness attesting to this fact.

Recently, there has been much excitement regarding the possibility of obtaining program obfuscation satisfying the \"indistinguishability obfuscation\" requirement: A transformation that takes a program and outputs an obfuscated version of it so that for any two functionally equivalent programs the output of the transformation is computationally indistinguishable.

Our main result is a construction of a computational secret-sharing scheme for any monotone function in NP assuming the existence of an efficient indistinguishability obfuscator for P and one-way functions. Furthermore, we show how to get the same result but relying on a weaker obfuscator: an efficient indistinguishability obfuscator for CNF formulas.

*18:17* [Pub][ePrint]
Attack On the Markov Problem, by James L. Adams
In 2000 Ko gave potential hard problem is proposed called the Markovproblem. We give an algorithm, for certain parameters, for solution of the Markov problem. The Markov problem is related to the knot recognition problem. Hence we also a new algorithm the knot recognition problem. This knot recognition algorithm may be used for previously proposed cryptosystem that uses knots.

*18:17* [Pub][ePrint]
Implementation and improvement of the Partial Sum Attack on 6-round AES, by Francesco Aldà and Riccardo Aragona and Lorenzo Nicolodi and Massimiliano Sala
The Partial Sum Attack is one of the most powerful attacks developed in the last 15years against reduced-round versions of AES. We introduce a slight improvement to

the basic attack which lowers the number of chosen plaintexts needed to successfully

mount it. Our version of the attack on 6-round AES can be carried out completely

in practice, as we demonstrate providing a full implementation. We also detail the

structure of our implementation, showing the performances we achieve.

*18:17* [Pub][ePrint]
A Forgery Attack against PANDA-s, by Yu Sasaki and Lei Wang
\\panda~is an authenticated encryption scheme designed by Ye {\\it et al.}, and submitted to the CAESAR competition.The designers claim that \\pandas, which is one of the designs of the \\panda-family, provides 128-bit security in the nonce misuse model.

In this note, we describe our forgery attack against \\pandas.

Our attack works in the nonce misuse model.

It exploits the fact that the message processing function and the finalization function are identical,

and thus a variant of the length-extension attack can be applied.

We can find a tag for a pre-specified formatted message with 2 encryption oracle calls, $2^{64}$ computational cost, and negligible memory.

*18:17* [Pub][ePrint]
A Practical Universal Forgery Attack against PAES-8, by Yu Sasaki and Lei Wang
\\paes~is an authenticated encryption scheme designed by Ye {\\it et al.},and submitted to the CAESAR competition.

The designers claim that \\paese, which is one of the designs of the \\paes-family,

provides 128-bit security in the nonce misuse model.

In this note, we show our forgery attack against \\paese.

Our attack works in the nonce misuse model.

The attack exploits the slow propagation of message differences.

The attack is very close to the universal forgery attack.

As long as the target message is not too short, {\\it e.g.} more than 10 blocks (160 bytes),

a tag is forged only with $2^{11}$ encryption oracle calls, $2^{11}$ computational cost, and negligible memory.

*18:13* [Job][New]
Doctoral Students (and Post-Doc), *Technische Universität Darmstadt, Germany*
The research group Computer Algebra and Cryptography at TU Darmstadt headed by Prof. Buchmann is looking for doctoral students. TU Darmstadt is a partner in the Center for Advanced Security Research Darmstadt CASED, one of the internationally leading research institutions in cyber security. The successful candidate will greatly benefit from the excellent CASED research environment.The applicants are expected to hold a master degree in computer science, mathematics, or a related area and to have a background in cryptography.

(1) We look for a doctoral student in the area of lattice-based cryptography at the earliest possible date. Lattice-based cryptography is a very promising direction in cryptography offering both (presumably) quantum immunity and additional features, e.g., fully homomorphic encryption. We are interested in both cryptanalysis (the concrete hardness of lattice problems) and the construction of provably secure and practical lattice-based schemes.

Previous experience in algebra, number theory, the geometry of numbers, and/or lattice-based cryptography is advantageous. The successful candidate will work in a research team of several doctoral students led by Dr. Özgür Dagdelen.

Please send your application to *lattice-position (at) cdc.inform*atik.tu-darmstadt.de.

(2) We offer a three-year position (doctoral student or postdoc) in a research project funded by the German Science Foundation DFG. The goal of this project is to integrate the hash-based signature scheme XMSS, invented in Darmstadt, into crypto-based security solutions such as SSL/TLS, HTTPS, S/MIME in collaboration with the company Genua mbH in Kirchheim.

Postdocs are also encouraged to apply here. Previous experience in the area of the project is advantageous. The successful candidate will work in a research team dealing with cryptography and crypto-based security solutions.

Please send your application to *ha
*