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00:17 [Pub][ePrint] Some Security Results of the RC4 + Stream Cipher, by Subhadeep Banik and Sonu Jha

  RC4+ stream cipher was proposed by Maitra et. al.

at Indocrypt 2008. It was claimed by the authors that this new

stream cipher is designed to overcome all the weaknesses reported

on the alleged RC4 stream cipher. In the design specifications of

RC4+, the authors make use of an 8-bit design parameter called

pad which is fixed to the value 0xAA. The first Distinguishing

Attack on RC4+ based on the bias of its first output byte was shown by Banik et. al. in Indocrypt 2013. In this paper, it was also mentioned that the distinguishing attack would still hold if the pad used in RC4+ is fixed to any even 8-bit constant other than 0xAA. Therefore, the question that arises is whether the design of RC4+ can be protected by fixing the pad parameter to some constant odd value. In this paper, we try to answer this very question. We show that the design is still vulnerable by mounting a distinguishing attack even if the pad is fixed to some constant 8-bit odd value. Surprisingly we find that if the value of the pad is made equal to 0x03, the design provides maximum resistance to distinguishing attacks. Lastly we return to the original cipher i.e. in which pad is set to 0xAA and unearth another bias in the second output byte of the cipher, thereby showing that practical implementations of this cipher should discard the use of the first two output bytes for encryption.

00:17 [Pub][ePrint] A Practical Attack Against the HIVE Hidden Volume Encryption System, by Kenneth G. Paterson and Mario Strefler

  The HIVE hidden volume encryption system was proposed by Blass et al. at ACM-CCS 2014. Even though HIVE has a security proof, this paper demonstrates an attack on its implementation that breaks the main security property claimed for the system by its authors, namely plausible hiding against arbitrary-access adversaries. Our attack is possible because of HIVE\'s reliance on the RC4 stream cipher to fill unused blocks with pseudorandom data. While the attack can be easily eliminated by using a better pseudorandom generator, it serves as an example of why RC4 should be avoided in all new applications and a reminder that one has to be careful when instantiating primitives.

15:17 [Pub][ePrint] Faulty Clock Detection for Crypto Circuits Against Differential Fault Analysis Attack , by Pei Luo and Yunsi Fei

  Clock glitch based Differential Fault Analysis (DFA) attack is a serious threat to cryptographic devices. Previous error detection schemes for cryptographic devices target improving the circuit reliability and cannot resist such DFA attacks. In this paper, we propose a novel faulty clock detection method which can be easily implemented either in FPGAs or integrated circuits to detect the glitches in system clock. Results show that the proposed method can detect glitches efficiently while needs very few system resource. It is also highly reconfigurable to tolerant clock inherent jitters, and will not involve complex design work for different processing technologies.

15:17 [Pub][ePrint] Efficient Stochastic Methods: Profiled Attacks Beyond 8 Bits, by Omar Choudary and Markus G. Kuhn

  Template attacks and stochastic models are among the most powerful

side-channel attacks. However, they can be computationally expensive

when processing a large number of samples. Various compression

techniques have been used very successfully to reduce the data

dimensionality prior to applying template attacks, most notably

Principal Component Analysis (PCA) and Fisher\'s Linear Discriminant

Analysis (LDA). These make the attacks more efficient computationally

and help the profiling phase to converge faster. We show how these

ideas can also be applied to implement stochastic models more

efficiently, and we also show that they can be applied and evaluated

even for more than eight unknown data bits at once.

15:17 [Pub][ePrint] Accountable Storage, by Giuseppe Ateniese and Michael T. Goodrich and Vassilios Lekakis and Charalampos Papamanthou and Evripidis Paraskevas and Roberto Tamassia

  We introduce Accountable Storage (AS), a framework allowing a client with small local space to outsource n file blocks to an untrusted server and be able (at any point in time after outsourcing) to provably compute how many bits have been discarded by the server.

Such protocols offer ``provable storage insurance\" to a client: In case of a data loss, the client can be compensated with a dollar amount proportional to the damage that has occurred, forcing the server to be more ``accountable\" for his behavior.

The insurance can be captured in the SLA between the client and the server.

Although applying existing techniques (e.g., proof-of-storage protocols) could address the problem,

the related costs of such approaches are prohibitive. Instead, our protocols can provably compute the damage that has occurred through an efficient recovery process of the lost or corrupted file blocks, which requires only sublinear $O(\\delta\\log n)$ communication, computation and local space, where $\\delta$ is the maximum number of corrupted file blocks that can be tolerated. Our technique is based on an extension of invertible Bloom filters, a data structure used to quickly compute the distance between two sets.

Finally, we show how our protocol can be integrated with Bitcoin,

to support automatic compensations proportional to the number of corrupted bits at the server. We also build and evaluate our protocols showing that they perform well in practice.

15:17 [Pub][ePrint] Hardware Implementation of Secure Shamir\'s Secret Sharing Scheme , by Pei Luo and Yu-Lun Lin and Zhen Wang and Mark Karpovsky

  Shamir\'s secret sharing scheme is an effective way to distribute secret to a group of shareholders. But this scheme is vulnerable to cheaters and attackers and thus how to protect the system from cheating and attacks is a big problem. In this paper, we proposed to use robust codes and algebraic manipulation detection (AMD) codes to protect the secret sharing module. Simulation and synthesis results show that the proposed architecture can improve the security level significantly even under strong cheating and attack models with some extra area and timing overheads.

15:17 [Pub][ePrint] Distance Lower Bounding, by Xifan Zheng and Reihaneh Safavi-Naini and Hadi Ahmadi

  Distance (upper)-bounding (DUB) allows a verifier to know whether a proving party is located within a certain distance bound. DUB protocols have many applications in secure authentication and location based services. We consider the dual problem of distance lower bounding (DLB), where the prover proves it is outside a distance bound to the verifier. We motivate this problem through a number of application scenarios, and model security against distance fraud (DF), Man-in-the-Middle (MiM), and collusion fraud (CF) attacks. We prove impossibility of security against these attacks without making physical assumptions. We propose approaches to the construction of secure protocols under reasonable assumptions, and give detailed design of our DLB protocol and prove its security using the above model. This is the first treatment of the DLB problem in the untrusted prover setting, with a number of applications and raising new research questions. We discuss our results and propose directions for future research.

15:17 [Pub][ePrint] Efficient Zero-Knowledge Proofs for Commitments from Learning With Errors over Rings, by Fabrice Benhamouda and Stephan Krenn and Vadim Lyubashevsky and Krzysztof Pietrzak

  We design an efficient commitment scheme, and companion zero-knowledge proofs of knowledge, based on the learning with errors over rings (RLWE) problem. In particular, for rings in which almost all elements have inverses, we construct a perfectly binding commitment scheme whose hiding property relies on the RLWE assumption. Our scheme maps elements from the ring (or equivalently, n elements from F_q) to a small constant number of ring elements. We then construct Sigma-protocols for proving, in a zero-knowledge manner, knowledge of the message contained in a commitment. We are able to further extend our basic protocol to allow us to prove additive and multiplicative relations among committed values.

Our protocols have a communication complexity of O(Mn\\log q) and achieve a negligible knowledge error in one run.

Here M is the constant from a rejection sampling technique that we employ, and can be set close to 1 by adjusting other parameters.

Previously known Sigma-protocols for LWE-related languages either relied on ``smudging\'\' out the error (which necessitates working over large fields, resulting in poor efficiency) or only achieved a noticeable or even constant knowledge error (thus requiring many repetitions of the protocol).

15:17 [Pub][ePrint] Fast Evaluation of Polynomials over Binary Finite Fields and Application to Side-channel Countermeasures, by Jean-Sebastien Coron and Arnab Roy and Srinivas Vivek

  We describe a new technique for evaluating polynomials over binary finite fields. This is useful in the context of anti-DPA countermeasures when an S-box is expressed as a polynomial over a binary finite field. For $n$-bit S-boxes our new technique has heuristic complexity ${\\cal O}(2^{n/2}/\\sqrt{n})$ instead of ${\\cal O}(2^{n/2})$ proven complexity for the Parity-Split method. We also prove a lower bound of ${\\Omega}(2^{n/2}/\\sqrt{n})$ on the complexity of any method to evaluate $n$-bit S-boxes; this shows that our method is asymptotically optimal. Here, complexity refers to the number of non-linear multiplications required to evaluate the polynomial corresponding to an S-box.

In practice we can evaluate any $8$-bit S-box in $10$ non-linear multiplications instead of $16$ in the Roy-Vivek paper from CHES 2013, and the DES S-boxes in $4$ non-linear multiplications instead of $7$. We also evaluate any $4$-bit S-box in $2$ non-linear multiplications instead of $3$. Hence our method achieves optimal complexity for the PRESENT S-box.

15:17 [Pub][ePrint] Conversion from Arithmetic to Boolean Masking with Logarithmic Complexity, by Jean-Sebastien Coron and Johann Groszschaedl and Praveen Kumar Vadnala and Mehdi Tibouchi

  A general method to protect a cryptographic algorithm against side-channel attacks consists in masking all intermediate variables with a random value. For cryptographic algorithms combining Boolean operations with arithmetic operations, one must then perform conversions between Boolean masking and arithmetic masking. At CHES 2001, Goubin described a very elegant algorithm for converting from Boolean masking to arithmetic masking, with only a constant number of operations. Goubin also described an algorithm for converting from arithmetic to Boolean masking, but with O(k) operations where k is the addition bit size. In this paper we describe an improved algorithm with time complexity O(log k) only. Our new algorithm is based on the Kogge-Stone carry look-ahead adder, which computes the carry signal in O(log k) instead of O(k) for the classical ripple carry adder. We also describe an algorithm for performing arithmetic addition modulo 2^k directly on Boolean shares, with the same complexity O(log k) instead of O(k). We prove the security of our

new algorithms against first-order attacks.

15:17 [Pub][ePrint] Breaking Existential Unforgeability of a Signature Scheme from Asiacrypt 2014, by Georg Fuchsbauer

  We show how to compute an existential forgery after querying 4 signatures on chosen messages for a signature scheme presented at Asiacrypt 2014.