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2014-12-25
17:10 [PhD][Update] Pascal Junod: Statistical cryptanalysis of block ciphers

  Name: Pascal Junod
Topic: Statistical cryptanalysis of block ciphers
Category:secret-key cryptography

Description:

Since the development of cryptology in the industrial and academic worlds in the seventies, public knowledge and expertise have grown in a tremendous way, notably because of the increasing, nowadays almost ubiquitous, presence of electronic communication means in our lives. Block ciphers are inevitable building blocks of the security of various electronic systems. Recently, many advances have been published in the ?eld of public-key cryptography, being in the understanding of involved security models or in the mathematical security proofs applied to precise cryptosystems. Unfortunately, this is still not the case in the world of symmetric-key cryptography and the current state of knowledge is far from reaching such a goal. However, block and stream ciphers tend to counterbalance this lack of “provable security” by other advantages, like high data throughput and ease of implementation.

In the ?rst part of this thesis, we would like to add a (small) stone to the wall of provable security of block ciphers with the (theoretical and experimental) statistical analysis of the mechanisms behind Matsui’s linear cryptanalysis as well as more abstract models of attacks. For this purpose, we consider the underlying problem as a statistical hypothesis testing problem and we make a heavy use of the Neyman-Pearson paradigm. Then, we generalize the concept of linear distinguisher and we discuss the power of such a generalization. Furthermore, we introduce the concept of sequential distinguisher, based on sequential sampling, and of aggregate distinguishers, which allows to build sub-optimal but efficient distinguishers. Finally, we propose new attacks against reduced-round versions of the block cipher IDEA.

In the second part, we propose the design of a new family of block ciphers named FOX. First, we study the efficiency of optimal diffusive components when implemented on low-cost architectures, and we present several new constructions of MDS matr[...]


17:08 [PhD][New]

 

17:08 [PhD][New] Ludovic Perret: Algebraic and Combinatorial Tools for Public Key Cryptography

  Name: Ludovic Perret
Topic: Algebraic and Combinatorial Tools for Public Key Cryptography
Category: public-key cryptography



16:17 [Pub][ePrint]

 

08:49 [Job][Update]

 

07:17 [Pub][ePrint] A pure block chain based decentralized exchange., by Harsh Patel

  A pure peer to peer version of the exchange system would allow all parties access to the market without relying on any central organization for market access. Paper proposes a solution for the problem of maintain an order book and determine the execution rate in the peer to peer network. Like crypto-currencies the network relies on blockchain of transaction. Digital signature system would be the core of the decentralized market place. The paper defines basic ground rules for the working of decentralized exchange. The major components of the decentralized exchange are issuing process, co-existence of blockchain and order books and functions of the miner. Unlike other crypto currencies de-centralized exchange would have a trust based issuing process which in long run would be a sum zero game. The decentralized

Exchange would have 3 types of entities namely - Issuer, Trader and Miner.



07:17 [Pub][ePrint] Simple composition theorems of one-way functions -- proofs and presentations, by Jaime Gaspar and Eerke Boiten

  One-way functions are both central to cryptographic theory and a clear example of its complexity as a theory. From the aim to understand theories, proofs, and communicability of proofs in the area better, we study some small theorems on one-way functions, namely: composition theorems of one-way functions of the form \"if $f$ (or $h$) is well-behaved in some sense and $g$ is a one-way function, then $f \\circ g$ (respectively, $g \\circ h$) is a one-way function\".

We present two basic composition theorems, and generalisations of them which may well be folklore. Then we experiment with different proof presentations, including using the Coq theorem prover, using one of the theorems as a case study.



07:17 [Pub][ePrint] Fair Multiple-bank E-cash in the Standard Model, by Jiangxiao Zhang and Yanwu Gao and Chunhui Feng and Hua Guo and Zhoujun Li

  Multiple-bank e-cash (electronic cash) model allows users and merchants to open their accounts at different banks which are monitored by the Center Bank. Some multiple-bank e-cash systems were proposed in recent years. However, prior implementations of multiple-bank e-cash all require the random oracle model idealization in their security analysis. We know some schemes are secure in the random oracle model, but are trivially insecure under any instantiation of the oracle.

In this paper, based on the automorphic blind signature, the Groth-Sahai proof system and a new group blind signature, we construct a fair multiple-bank e-cash scheme. The new scheme is proved secure in the standard model and provides the following

functionalities, such as owner tracing, coin tracing, identification of the double spender and

signer tracing. In order to sign two messages at once, we extend Ghadafi\'s group blind signature to a new group blind signature. The new signature scheme may be of independent interest.



07:17 [Pub][ePrint] DTLS-HIMMO: Efficiently Securing a Post-Quantum World with a Fully-Collusion Resistant KPS, by Oscar Garcia-Morchon and Ronald Rietman and Sahil Sharma and Ludo Tolhuizen and Jose Luis Torre-Arce

  The future development of quantum-computers could turn many key agreement algorithms used in the Internet today fully insecure, endangering many applications such as online banking, e-commerce, e-health, etc. At the same time, the Internet is further evolving to enable the Internet of Things (IoT) in which billions of devices

deployed in critical applications like healthcare, smart cities

and smart energy are being connected to the Internet. The IoT not only requires strong and quantum-secure security, as current Internet applications, but also efficient operation. The recently introduced HIMMO scheme enables lightweight identity-based key sharing and verification of credentials in a non-interactive way. The collusion resistance properties of HIMMO enable direct secure communication between any pair of Internet-connected devices. The facts that attacking HIMMO requires lattice techniques and that it is extremely lightweight make HIMMO an ideal lightweight approach for key agreement and information verification in a post-quantum world.

Building on the HIMMO scheme, this paper firstly shows how HIMMO can be efficiently implemented even in resource-constrained devices enabling combined key agreement and credential verification one order of magnitude more efficiently than using ECDH-ECDSA, while being

quantum secure. We further explain how HIMMO helps to secure the Internet and IoT by introducing the DTLS- HIMMO operation mode. DTLS, the datagram version of TLS, is becoming the standard security protocol in the IoT, however, it is very frequently discussed that it does not offer the right performance for IoT scenarios. Our design,

implementation, and evaluation show that DTLS-HIMMOoperation mode achieves the security properties of DTLS Certificate security suite while being quantum secure and exhibiting the overhead of symmetric-key primitives.





2014-12-24
07:10 [Event][New] SAC'15: Selected Areas in Cryptography 2015

  Submission: 25 May 2015
Notification: 6 July 2015
From August 12 to August 14
Location: Sackville, Canada
More Information: http://mta.ca/sac2015/




2014-12-22
16:41 [PhD][Update] Olivier Billet: Cryptologie multivariable

  Name: Olivier Billet
Topic: Cryptologie multivariable
Category:(no category)