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2014-12-27
01:17 [Pub][ePrint] Double-and-Add with Relative Jacobian Coordinates, by Björn Fay

  One of the most efficient ways to implement a scalar multiplication on elliptic curves with precomputed points is to use mixed coordinates (affine and Jacobian). We show how to relax these preconditions by introducing relative Jacobian coordinates and give an algorithm to compute a scalar multiplication where the precomputed points can be given in Jacobian coordinates. We also show that this new approach is compatible with Meloni\'s trick, which was already used in other papers to reduce the number of multiplications needed for a double-and-add step to 18 field multiplications.



01:17 [Pub][ePrint] Compact Accumulator using Lattices, by Mahabir Prasad Jhanwar and Reihaneh Safavi-Naini

  An accumulator is a \\textit{succinct} aggregate of a set of values where it is possible to issue \\textit{short} membership proofs for each accumulated value. A party in possession of such a membership proof can then demonstrate that the value is included in the set. In this paper, we preset the first lattice-based accumulator scheme that issues compact membership proofs. The security of our scheme is based on the hardness of Short Integer Solution ($\\mathsf{SIS}$) problem.



01:17 [Pub][ePrint] Modified SIMON and SPECK: Lightweight Hybrid Design for Embedded Security, by GAURAV BANSOD, NISHCHAL RAVAL, NARAYAN PISHAROTY, ABHIJIT PATIL

  Lightweight cryptography is an emerging field that will play a critical role in areas like pervasive computing and Internet of Things (IoT). In recent years, many lightweight ciphers have been designed that are better suited for small scale embedded security. Lightweight ciphers like PRESENT, KLEIN, Hummingbird 2, XTEA, CLEFIA etc. are the ciphers known for compact hardware implementations. Recently SIMON and SPECK ciphers have been introduced which are Feistel based designs. SIMON and SPECK are flexible and are having very less memory requirements and better performance in both hardware and software. There is always a tradeoff between security and performance. Strengthening the design of these ciphers will increase their acceptability for all embedded applications. In this paper, we have proposed a novel approach which increases the strength and performance of SIMON and SPECK. Further a confusion layer is added in the design of the newly designed cipher RECTANGLE. RECTANGLE has a robust S-box as compared to other lightweight ciphers which makes the design fast and efficient. We have added the substitution property to the SIMON and SPECK cipher after analyzing the cryptanalysis properties of both the ciphers. S-box of RECTANGLE is best suited for SIMON and SPECK because the SIMON and SPECK designs have an asymmetric permutation which is the basic requirement for RECTANGLE. Combination of S-box and asymmetric permutation together achieves a robust design. The hybrid design proposed in this paper needs less memory space as compared to the existing ciphers. This approach makes SIMON and SPECK design more robust and resistive against all possible attacks due to the addition of the non-linear substitution layer. This robust design will have a positive impact in the field of lightweight cryptosystems.





2014-12-26
19:17 [Pub][ePrint] On Continuous After-the-Fact Leakage-Resilient Key Exchange, by Mohsen Toorani

  Side-channel attacks are severe type of attack against implementation of cryptographic primitives. Leakage-resilient cryptography is a new theoretical approach to formally address the problem of side-channel attacks. Recently, the Continuous After-the-Fact Leakage (CAFL) security model has been introduced for two-party authenticated key exchange (AKE) protocols. In the CAFL model, an adversary can adaptively request arbitrary leakage of long-term secrets even after the test session is activated. It supports continuous leakage even when the adversary learns certain ephemeral secrets or session keys. The amount of leakage is limited per query, but there is no bound on the total leakage. A generic leakage-resilient key exchange protocol $\\pi$ has also been introduced that is formally proved to be secure in the CAFL model. In this paper, we comment on the CAFL model, and show that it does not capture its claimed security. Furthermore, we present an attack and counterproofs for the security of protocol $\\pi$ which invalidates the formal security proofs of protocol $\\pi$ in the CAFL model.



19:17 [Pub][ePrint] Proof-of-Work as Anonymous Micropayment: Rewarding a Tor Relay, by Alex Biryukov and Ivan Pustogarov

  In this paper we propose a new micropayments scheme which can be used to

reward Tor relay operators. Tor clients do not pay Tor relays with

electronic cash directly but submit proof of work shares which the

relays can resubmit to a crypto-currency mining pool. Relays credit

users who submit shares with

tickets that can later be used to purchase improved service. Both shares

and tickets when sent over Tor circuits are anonymous. The analysis of

the crypto-currencies market prices shows that the proposed scheme can

compensate significant part of Tor relay operator\'s expenses.





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.