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Computing isogenies between elliptic curves is a significant part of post-quantum cryptography with many practical applications (for example, in SIDH, SIKE, B-SIDH, or CSIDH algorithms). Comparing to other post-quantum algorithms, the main advantages of these protocols are smaller keys, the similar idea as in the ECDH, and a large basis of expertise about elliptic curves. The main disadvantage of the isogeny-based cryptosystems is their computational efficiency - they are slower than other post-quantum algorithms (e.g., lattice-based). That is why so much effort has been put into improving the hitherto known methods of computing isogenies between elliptic curves. In this paper, we present new formulas for computing isogenies between elliptic curves in the extended Jacobi quartic form with two methods: by transforming such curves into the short Weierstrass model, computing an isogeny in this form and then transforming back into an initial model or by computing an isogeny directly between two extended Jacobi quartics. [ABSTRACT FROM AUTHOR]

We show unconditionally that the existence of commitment schemes implies the existence of constant-round nonmalleable commitments; earlier protocols required additional assumptions such as collision-resistant hash functions or subexponential one-way functions. Our protocol also satisfies the stronger notions of concurrent nonmalleability and robustness. As a corollary, we establish that constant-round nonmalleable zero-knowledge arguments for NP can be based on one-way functions and constant-round secure multiparty computation can be based on enhanced trapdoor permutations; also here, earlier protocols additionally required either collision-resistant hash functions or subexponential one-way functions. [ABSTRACT FROM AUTHOR]

We study the problem of "privacy amplification": key agreement between two parties who both know a weak secret w, such as a password. (Such a setting is ubiquitous on the internet, where passwords are the most commonly used security device.) We assume that the key agreement protocol is taking place in the presence of an active computationally unbounded adversary Eve. The adversary may have partial knowledge about w, so we assume only that w has some entropy from Eve's point of view. Thus, the goal of the protocol is to convert this nonuniform secret w into a uniformly distributed string R that is fully secret from Eve. R may then be used as a key for running symmetric cryptographic protocols (such as encryption, authentication, etc.). Because we make no computational assumptions, the entropy in R can come only from w. Thus, such a protocol must minimize the entropy loss during its execution, so that R is as long as possible. The best previous results have entropy loss of Θ(κc²), where κ is the security parameter, thus requiring the password to be very long even for small values of κ. In this work, we present the first protocol for information-theoretic key agreement that has entropy loss linear in the security parameter. The result is optimal up to constant factors. We achieve our improvement through a somewhat surprising application of error-correcting codes for the edit distance. The protocol can be extended to provide also "information reconciliation," that is, to work even when the two parties have slightly different versions of w (e.g., when biometrics are involved). [ABSTRACT FROM AUTHOR]

The Chow parameters of a Boolean function f : {-1, 1}n → {-1, 1} are its n + 1 degree-0 and degree-1 Fourier coefficients. It has been known since 1961 [Chow 1961; Tannenbaum 1961] that the (exact values of the) Chow parameters of any linear threshold function f uniquely specify f within the space of all Boolean functions, but until recently [O'Donnell and Servedio 2011] nothing was known about efficient algorithms for reconstructing f (exactly or approximately) from exact or approximate values of its Chow parameters. We refer to this reconstruction problem as the Chow Parameters Problem. Our main result is a new algorithm for the Chow Parameters Problem which, given (sufficiently accurate approximations to) the Chow parameters of any linear threshold function f, runs in time Õ(n²) ⋅ (1/∈) O(log²(1/∈)) and with high probability outputs a representation of an LTF f' that is ∈-close to f in Hamming distance. The only previous algorithm [O'Donnell and Servedio 2011] had running time poly(n) ⋅ 2²(1/∈²). As a byproduct of our approach, we show that for any linear threshold function f over {-1, 1} n, there is a linear threshold function f' which is ∈-close to f and has all weights that are integers of magnitude at most √n ⋅ (1/∈)O(log²(1/∈)). This significantly improves the previous best result of Diakonikolas and Servedio [2009] which gave a poly(n) ⋅ 2Õ(1/∈2/3) weight bound, and is close to the known lower bound of max{√n, (1/∈) Ω(log log(1/∈))} [Goldberg 2006; Servedio 2007]. Our techniques also yield improved algorithms for related problems in learning theory. In addition to being significantly stronger than previous work, our results are obtained using conceptually simpler proofs. The two main ingredients underlying our results are (1) a new structural result showing that for f any linear threshold function and g any bounded function, if the Chow parameters of f are close to the Chow parameters of g then f is close to g; (2) a new boosting-like algorithm that given approximations to the Chow parameters of a linear threshold function outputs a bounded function whose Chow parameters are close to those of f . [ABSTRACT FROM AUTHOR]

Noninteractive zero-knowledge (NIZK) proof systems are fundamental primitives used in many cryptographic constructions, including public-key encryption secure against chosen ciphertext attack, digital signatures, and various other cryptographic protocols. We introduce new techniques for constructing NIZK proofs based on groups with a bilinear map. Compared to previous constructions of NIZK proofs, our techniques yield dramatic reduction in the length of the common reference string (proportional to security parameter) and the size of the proofs (proportional to security parameter times the circuit size). Our novel techniques allow us to answer several long-standing open questions in the theory of noninteractive proofs. - We construct the first perfect NIZK argument system for all NP. - We construct the first universally composable NIZK argument for all NP in the presence of an adaptive adversary. - We construct a non-interactive zap for all NP, which is the first that is based on a standard cryptographic security assumption. [ABSTRACT FROM AUTHOR]

The article presents the front cover of the periodical "Journal of Mathematical Cryptology", along with the names of the editorial board, publishing details such as disclaimers, and table of contents which includes Cartesian codes, linear algebra and geometry.

Two visual models of image secret sharing have been studied: visual cryptography schemes (VCS), introduced by Naor and Shamir, and visual cryptograms of random grids (VCRG), introduced by Kafri and Keren. VCRG has gained much attention in academia than before to avoid the pixel expansion of VCS. Although there is a strict relation between VCRG and VCS, VCRG can still be improved to achieve a better result. In this paper, based on new insight into linear algebraic technique to construct VCS, where we are able to construct VCS by solving a linear system of more equations at a time, we put forward a new construction of VCRG for general access structures. The effectiveness and advantage of the proposed construction are formally analyzed and experimentally demonstrated. With theoretical and practical interests, our construction exposes new possibilities to the researches of visual models of image secret sharing. [ABSTRACT FROM AUTHOR]

Steganography is a means of covert communication without revealing the occurrence and the real purpose of communication. The adaptive multirate wideband (AMR-WB) is a widely adapted format in mobile handsets and is also the recommended speech codec for VoLTE. In this paper, a novel AMR-WB speech steganography is proposed based on diameter-neighbor codebook partition algorithm. Different embedding capacity may be achieved by adjusting the iterative parameters during codebook division. The experimental results prove that the presented AMR-WB steganography may provide higher and flexible embedding capacity without inducing perceptible distortion compared with the state-of-the-art methods. With 48 iterations of cluster merging, twice the embedding capacity of complementary-neighbor-vertices-based embedding method may be obtained with a decrease of only around 2% in speech quality and much the same undetectability. Moreover, both the quality of stego speech and the security regarding statistical steganalysis are better than the recent speech steganography based on neighbor-index-division codebook partition. [ABSTRACT FROM AUTHOR]

Attribute-based signature (ABS) is a novel cryptographic primitive, which can make the signing party sign a message with fine-grained control over identifying information. ABS only reveals the fact that the verified message must be signed by a user with a set of attributes satisfying a predicate. Thus, ABS can hide any identifying information and make fine-grained control on signing. Presently, many attribute-based signature schemes have been proposed, but most of them are not very efficient. Maji et al. recently presented a complete definition and construction about ABS for monotone predicates and showed three instantiations under their framework for ABS. Although the most practical one of their instantiations is efficient, the instantiation is constructed in the generic group model and has been proved to be insecure. Then, Okamoto et al. proposed an attribute-based signature scheme in the standard model, which can support generalized non-monotone predicates over access structure. However, their scheme is not efficient in practice. In this paper, we present a framework for ABS and show a detailed security model for ABS. Under our framework, we present an attribute-based signature scheme for monotone predicates in the standard model, where we choose the Waters' signature scheme as the prototype of our attribute-based signature scheme. Compared with the Maji's scheme in the generic group model, the proposed scheme is constructed in the standard model. Furthermore, compared with the Okamoto's scheme, the proposed scheme is more efficient by decreasing the computation cost. [ABSTRACT FROM AUTHOR]

In view of research on fully homomorphic encryption scheme proposed by Zvika Brakerski in 2012, we find it is not much efficient, because it requests that $$q/B \ge (O(nlogq))^{L+O(1)}$$ , and can encrypt only one message at a time. In this paper, we have proved that STP-binary-LWE is hard when LWE is hard, and have modified the fully homomorphic encryption scheme based on STP-Binary-LWE so that it only requests $$q/B \ge (O(nlog(logn)))^{L+O(1)}$$ . It is within the reach of the scheme to encrypt several messages at a time and give consideration to both security and efficiency in the hierarchical encryption systems. [ABSTRACT FROM AUTHOR]

Biometric-based cryptographic key generation is regarded as a data mining approach that uses knowledge discovery techniques to extract biometric information to generate cryptographic keys for protecting secured data by encryption. This application has been widely used in security systems to limit the weakness of passwords. Although conventional biometrics such as fingerprint, face, voice, and handwriting contain biometric information that is unique and repeatable for each individual, they are difficult to change to be used in different purposes. In this paper, we propose a system to exploit human electroencephalography (EEG) data as a new biometric for cryptographic key generation. This system provides high potential because EEG is impossible to be faked or compromised. Our method is evaluated using the EEG Alcoholism and GrazIIIa datasets, and is shown to reliably produce secure cryptographic keys with a 99% success rate. [ABSTRACT FROM AUTHOR]

This article explains, demonstrates, and evaluates Chaum’s protocol for detecting a man-in-the-middle (MitM) of text-messaging network communications. MitM attacks pose serious risks to many network communications. Networks often mitigate these risks with robust protocols, such as TLS, which assume some type of public-key infrastructure that provides a mechanism for the authenticated exchange of public keys. By contrast, Chaum’s protocol aims to detect a MitM withminimalassumptions and technology, and in particular without assuming the authenticated exchange of public keys. Chaum assumes that the eavesdropper can “sound like” the communicants but that the eavesdropper cannot fabricate sensible conversations. Using an encryption function and one-way function, Chaum’s protocol works in three phases. In Phase I, the communicants exchange their public keys. In Phase II, each communicant generates a random string. The first communicant cryptographically commits to that string, and sends the string to the other communicant after receiving the other’s string. In Phase III, using any of four different “scenarios” the communicants verify that each possesses the same two strings. The protocol forces any MitM to cause the communicants to possess different pairs of strings. The text-messaging scenario is similar to a forced-latency protocol proposed by Wilcox-O’Hearn in 2003. This article implements and experimentally demonstrates the effectiveness of the third scenario, which uses timing to detect a MitM in text-messaging. Even assuming a MitM can send messages without any network latency, the protocol forces the MitM to cause delays noticeable by the communicants. This article is the first to explain, demonstrate, and evaluate Chaum’s protocol, which Chaum described only in an abandoned and nearly inscrutable patent application. [ABSTRACT FROM AUTHOR]

The article presents research on the significance of rapid data exchange in keeping a secret for 24 hours at the University of Geneva in Switzerland. Topics discussed include the use of cryptography in sending coded messages, the complementary cryptographic tasks, and the association of physics-based information security with quantum mechanics.

Steganography is the art of science of hiding information which is more useful in many social networks, digital media, and printing material. Many hiding algorithms are used to flourish the security level of the recent wireless multimedia system to protect the data from an attacker. This paper describes about existing steganographic based hiding methods using LSB techniques, RSA algorithm, DNA cryptography and DNA steganography, which is used to prevent copying, forgery and unauthorized access of videos, audios and images. Existing hiding methods had demerit of increased key size, computational cost, speed and size of the input. Thus the DNA steganography based Hyperelliptic Curve Cryptography (HECC) is proposed which provides a higher level of security to image file and also assure the digital media security. The proposed HECC based DNA steganography is compared with traditional cryptographic techniques results in 30 and 42 % increased processing time for encryption process and decryption process respectively. Finally, the proposed scheme is compared with other traditional steganographic technique in terms of Mean Square Error, Peak Signal to Noise Ratio (PSNR), embedding capacity. From the simulation results, it is inferred that, the proposed steganographic method has, the less embedding capacity, high MSR and PSNR value compared with other steganographic methods. [ABSTRACT FROM AUTHOR]

Asymmetric group key agreement is a cryptographic primitive allowing a group of users to negotiate a common public encryption key while each of them holds a different secret private decryption key. Anyone (including outsiders) with the public encryption key can send encrypted messages to the group members, and then the group members can decrypt the messages. Authenticated key agreement protocols authenticate the identities of users to ensure that only the intended group members can establish a session in which the group members can communicate with each other. Dynamic asymmetric group key agreement concerns about the scenarios such as ad hoc networks in which the group members may join or leave at any given time. In this paper, we propose a one-round authenticated dynamic protocol for symmetric group key agreement. For efficiency reasons, we employ the identity-based public-key cryptography (IB-PKC) to authenticate users rather than the public key infrastructure and the certificate-less public-key cryptography. Our analysis shows that the proposals in the paper can resist active attacks and meet many desirable security attributes. Besides, our protocol allows users to join or leave the group at the same time. Furthermore, our protocol is round-optimal and has a quite good performance as compared with previous works. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An aggregate signature refers to a signature, by which n signatures σ1,..., σ n corresponding to n messages m1,..., m n and n users u1,..., u n can be transformed into a single short signature [ABSTRACT FROM AUTHOR]

Due to the proliferation of side-channel attacks, many efforts have been made to construct cryptographic systems that remain provably secure even if part of the secret information is leaked to the adversary. Recently, there have been many identity-based encryption (IBE) schemes proposed in this context, almost all of which, however, can only achieve chosen plaintext attack (CPA) security. As far as we know, Alwen et al.'s IBE is the unique practical scheme secure against adaptive chosen ciphertext attacks (CCA2) in the standard model. Unfortunately, this scheme suffers from an undesirable shortcoming that the leakage parameter λ and the message length m are subject to λ + m≤ log p − ω(log κ), where κ and p denote the security parameter and the prime order of the underlying group, respectively. Beyond that, the leakage ratio in this scheme is very low, which can just reach 1/6. In this work, we put forward two new IBE schemes, both of which are λ-leakage-resilient CCA2 secure in the standard model. Specifically, the first construction is proposed based on Gentry's IBE, which is quite practical and almost as efficient as the original scheme. Moreover, its leakage parameter, λ≤ log p − ω(log κ), is independent of the size of the message space. To the best of our knowledge, it is the first practical leakage-resilient fully CCA2 secure IBE scheme in the standard model, tolerating up to (log p − ω(log κ))-bit leakage of the private key and its leakage parameter being independent of the message length. As to the second construction, it is proposed based on the scheme of Alwen et al., which has the same leakage parameter as Alwen et al., but has a better efficiency performance and a higher leakage ratio. As far as we know, it is the first practical and fully CCA2 secure leakage-resilient IBE scheme with leakage ratio up to 1/4. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Compared with the visual-cryptography-based visual secret sharing, the random-grid-based visual secret sharing (RGVSS) has some technical advantages, such as no pixel expansion and no need of codebooks. Designed based on RGVSS, the user-friendly random-grid-based visual secret sharing (UFRGVSS) not only inherits the advantages of RGVSS but also overcomes the data management problem in RGVSS by taking meaningful images as shares. Unfortunately, up to now, the existing threshold UFRGVSS schemes are only (2, 2) ones, which should use two meaningful images with complementary colors as shares. What's more, there is no feasible method to construct UFRGVSS schemes for more general threshold access structures excluding (2, 2) threshold, let alone for general access structures (GASs). Motivated by these concerns, in this paper, by stamping the gray-scale images with the shares generated from the traditional RGVSS, a novel method was proposed to design the UFRGVSS scheme for GASs, in which the resulting shares can be any meaningful gray-scale images. Experimental results show the feasibility of the proposed method by assessing its performance under different situations. Literature retrieval shows that our work may be the first attempt to construct the UFRGVSS scheme for GASs. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

White-box cryptography aims at implementing a cipher to protect its key from being extracted in a white-box attack context, where an attacker has full control over dynamic execution of the cryptographic software. So far, most white-box implementations exploit lookup-table-based techniques and have been broken because of a weakness that the embedded large linear encodings are cancelled out by compositions of lookup tables. In this paper, we propose a new lookup-table-based white-box implementation for the Chinese block cipher standard SM4 that can protect the large linear encodings from being cancelled out. Our implementation, which can resist a series of white-box attacks, requires 32.5MB of memory to store the lookup tables and is about nine times as fast as the previous Xiao-Lai white-box SM4 implementation. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Introduction of various cryptographic modes of operation is induced with noted imperfections of symmetric block algorithms. Design of some cryptographic modes of operation has already been exploited as an idea for parallelization of certain algorithms execution. To the best of our knowledge, there is no evidence in the available literature that output feedback (OFB) mode, which is used in satellite communications, has ever been parallelized. In this paper, we consider the performance of a convenient mode of operation, which performs tweakable parallel encryption using xor encrypt xor (XEX) and xor encrypt (XE) constructions in OFB like mode. We make use of an idea similar to the XTS-AES in order to create two parallel tweakable block ciphers. The first of them is designed using XEX construction, while the second is based on XE construction. Each cipher uses two threads to produce corresponding keystreams. Keystreams are first merged with each other and then used in modified tweakable parallel OFB mode of operation. As a proof of the concept, we have implemented a Java application in which these parallel solutions are applied to collect empirical data. The results obtained show that under certain conditions tweakable parallel OFB modes using XEX and XE constructions can achieve performance accelerations up to 10% and to 20%, respectively. Copyright © 2015 John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

The situation for post-challenge continuous auxiliary input leakage has not been considered in the cryptography schemes for previous literature. We present a semantic-security model with post-challenge continuous auxiliary inputs for identity-based encryption. In this model, the adversary is permitted to obtain some information of the private keys constantly and to query more information after seeing the challenge ciphertext through the side-channel attacks. Furthermore, we present an identity-based encryption scheme resilient to leakage under composite order groups. Our scheme is secure against post-challenge continuous auxiliary input, adaptive chosen-identity, and adaptive chosen plaintext attacks under three static assumptions in the standard model. Compared with existing identity-based encryption schemes under security properties and performance, our scheme is practical. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Pervasive computing constitutes a growing trend, aiming to embed smart devices into everyday objects. The limited resources of these devices and the ever-present need for lower production costs, lead to the research and development of lightweight cryptographic mechanisms. Block ciphers, the main symmetric key cryptosystems, perform well in this field. Nevertheless, stream ciphers are also relevant in ubiquitous computing applications, as they can be used to secure the communication in applications where the plaintext length is either unknown or continuous, like network streams. This paper provides the latest survey of stream ciphers for embedded systems. Lightweight implementations of stream ciphers in embedded hardware and software are examined as well as relevant authenticated encryption schemes. Their speed and simplicity enable compact and low-power implementations, allow them to excel in applications pertaining to resource-constrained devices. The outcomes of the International Organization for Standardization/International Electrotechnical Commission 29192-3 standard and the cryptographic competitions eSTREAM and Competition for Authenticated Encryption: Security, Applicability, and Robustness are summarized along with the latest results in the field. However, cryptanalysis has proven many of these schemes are actually insecure. From the 31 designs that are examined, only six of them have been found to be secure by independent cryptanalysis. A constrained benchmark analysis is performed on low-cost embedded hardware and software platforms. The most appropriate and secure solutions are then mapped in different types of applications. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Providing secured and seamless service is one of the most important aspects of mobile networks, particularly for mobile WiMAX systems. However, the long delay handover schemes brought by the time-consuming EAP-based authentication may cause service disruption when a mobile WiMAX user moves between the coverage areas of different base stations. In this paper, we propose a handover scheme using symmetric key cryptography and pre-authentication approach to shorten the delay while ensuring high security level for Mobile WiMAX handover. The scheme is proven by BAN logic to achieve the security goals of an authentication scheme. A performance analysis is also carried out to show the effectiveness of this scheme in reducing handover delay and saving computational resources. [ABSTRACT FROM AUTHOR]

Statistical analysis of attacks on symmetric ciphers often requires assuming the normal behaviour of a test statistic. Typically such an assumption is made in an asymptotic sense. In this work, we consider concrete versions of some important normal approximations that have been made in the literature. To do this, we use the Berry-Esséen theorem to derive explicit bounds on the approximation errors. A basic mathematical requirement is that such approximation errors should be within reasonable bounds, a point which appears to have been overlooked in many of the earlier works on statistical aspects of cryptanalysis. Interpreting the error bounds in the cryptanalytic context yields several surprising results. One important implication is that this puts in doubt the applicability of the order statistics based approach for analysing key recovery attacks on block ciphers. This approach has been earlier used to obtain several results on the data complexities of (multiple) linear and differential cryptanalysis. The non-applicability of the order statistics based approach puts a question mark on the data complexities obtained using this approach. Fortunately, we are able to recover all of these results by utilising the hypothesis testing framework. This, however, necessitates using normal approximations for the χ² and the LLR test statistics considered in earlier works. These approximations themselves have issues which seem to be difficult to resolve satisfactorily. More generally, the message of our work is that all cryptanalytic attacks should properly derive and interpret the error bounds for any (normal) approximation that is made. [ABSTRACT FROM AUTHOR]

A hash function secure in the indifferentiability framework (TCC 2004) is able to resist all meaningful generic attacks. Such hash functions also play a crucial role in establishing the security of protocols that use them as random functions. To eliminate multi-collision type attacks on the Merkle-Damgård mode (Crypto 1989), Lucks proposed widening the size of the internal state of hash functions (Asiacrypt 2005). The fast wide pipe (FWP) hash mode was introduced by Nandi and Paul at Indocrypt 2010, as a faster variant of Lucks' wide pipe mode. Despite the higher speed, the proven indifferentiability bound of the FWP mode has so far been only up to the birthday barrier of n/2 bits. The main result of this paper is the improvement of the FWP bound to 2n/3 bits (up to an additive constant). We also provide evidence that the bound may be extended beyond 2n/3 bits. [ABSTRACT FROM AUTHOR]

Attribute-based Encryption (ABE) is regarded as a promising cryptographic conducting tool to guarantee data owners’ direct control over their data in public cloud storage. The earlier ABE schemes involve only one authority to maintain the whole attribute set, which can bring a single-point bottleneck on both security and performance. Subsequently, some multi-authority schemes are proposed, in which multiple authorities separately maintain disjoint attribute subsets. However, the single-point bottleneck problem remains unsolved. In this paper, from another perspective, we conduct a threshold multi-authority CP-ABE access control scheme for public cloud storage, named TMACS, in which multiple authorities jointly manage a uniform attribute set. In TMACS, taking advantage of ($t,n$ ) threshold secret sharing, the master key can be shared among multiple authorities, and a legal user can generate his/her secret key by interacting with any $t$ authorities. Security and performance analysis results show that TMACS is not only verifiable secure when less than $t$ authorities are compromised, but also robust when no less than $t$ authorities are alive in the system. Furthermore, by efficiently combining the traditional multi-authority scheme with TMACS, we construct a hybrid one, which satisfies the scenario of attributes coming from different authorities as well as achieving security and system-level robustness. [ABSTRACT FROM PUBLISHER]

We propose a loss tolerant quantum private query (QPQ) protocol based on two non-orthogonal states and unambiguous state discrimination (USD) measurement. By analyzing a two-point attack by a third party, we find that our protocol has a stronger ability to resist external attacks than G-protocol and Y-protocol. Our protocol requires a smaller number of compressions than that in G-protocol (Gao et al., Opt. Exp. 2012, 20, 17411-17420) and Y-protocol (Yan et al. Quant. Inf. Process. 2014, 13, 805-813), which means less post-processing. Our protocol shows better database security and user privacy compared with G-protocol. [ABSTRACT FROM AUTHOR]

The session initiation protocol (SIP) has been receiving a lot of attention to provide security in the Voice over IP (VoIP) in Internet and mobility management. Recently, Yeh et al. proposed a smart card-based authentication scheme for SIP using elliptic curve cryptography (ECC). They claimed that their scheme is secure against known security attacks. However, in this paper, we indicate that Yeh et al.'s scheme is vulnerable to off-line password guessing attack, user impersonation attack and server impersonation attack, in the case that the smart card is stolen and the information stored in the smart card is disclosed. As a remedy, we also propose an improved smart card-based authentication scheme which not only conquers the security weaknesses of the related schemes but also provides a reduction in computational cost. The proposed scheme also provides the user anonymity and untraceability, and allows a user to change his/her password without informing the remote server. To show the security of our protocol, we prove its security the random oracle model. [ABSTRACT FROM AUTHOR]

The paper is concerned with safety appraisal of safety-related communication systems (SRComSs) with open transmission system, where except in addition to message transmission integrity also confidentiality is recommended to be provided. The authors focused on safety analysis of safety-related messages transmission secured using cryptographic and safety code mechanisms and on the possibilities of modelling safety-related industrial communication system, where a high safety integrity level SIL3 is required to be guaranteed. The paper features mathematical procedures to calculate the rate of hazardous transmission failure of safety-related messages in the result of electromagnetic interference (EMI) effects in the communication channel and by the presence of random hardware failures of SRComS. The theoretical techniques and safety analyses emerge from risk analysis and are compared with the knowledge gained by the authors during safety verifications of such systems for transportation applications. It is a little explored area, because the standards concerning safety-related control systems (SRCSs) did not support any cryptography-based methods. A quantitative safety integrity analysis of SRComS is based on utilisation of Markov's processes. The proposed Markov's model is applied on an open transmission system built on the IEEE 802.llg standard, which is complemented by cryptographic and safety code. The calculations are performed using Mathematica software tool. The proposed base model is universal and can be modified (simplified) in dependence on the parameters of a specific SRComS. [ABSTRACT FROM AUTHOR]

This paper presents an all-digital true random number generator (TRNG) harvesting entropy from the collapse of two edges injected into one even-stage ring, fabricated in 40 and 180 nm CMOS technologies. A configurable ring and tuning loop provides robustness across a wide range of temperature (-40\,^\circ\textC to 120 °C), voltage (0.6 to 0.9 V), process variation, and external attack. The dynamic tuning loop automatically configures the ring to meet a sufficient collapse time, thereby maximizing entropy. Measured random bits pass all NIST randomness tests across all measured operating conditions and power supply attacks. In 40 nm, the TRNG occupies only 836\,\upmu \textm^2 and consumes 23 pJ/bit at nominal 0.9 V and 11 pJ/bit at 0.6 V. [ABSTRACT FROM PUBLISHER]

In their seminal work, Impagliazzo and Rudich (STOC'89) showed that no key-agreement protocol exists in the random-oracle model, yielding that key agreement cannot be black-box reduced to one-way functions. In this work, we generalize their result, showing that, to a large extent, no-private-input, semi-honest, two-party functionalities that can be securely implemented in the random oracle model can be securely implemented information theoretically (where parties are assumed to be all powerful, and no oracle is given). Using a recent information-theoretic impossibility result by McGregor et al. (FOCS'10), our result yields that certain functionalities (e.g. inner product) cannot be computed both in an accurately and in a differentially private manner in the random oracle model, implying that protocols for computing these functionalities cannot be black-box reduced to the existence of one-way functions. [ABSTRACT FROM AUTHOR]

Side Channel Attack (SCA) recovers secret information from an embedded device with implementation of cryptographic algorithm by exploiting its physical leakages. For most SCA methods to achieve good performance, the measured leakages are often desired to be well aligned. However, due to some specific reasons such as inaccurate measurements or carefully designed countermeasures, misalignment of leakages frequently occurs in practice. Misalignment significantly reduces the efficiency of SCA methods, or even makes them fail. To address this issue, two alignment approaches are proposed: a local alignment based on shotgun distance and a global alignment based on weighted edit distance. Compared with previous methods, the proposed methods are capable of keeping the secret dependant leakages, while not introducing any redundant information. In addition, the proposed methods could also reduce the negative effects of noise, which is another factor seriously decreasing the efficiency of SCA methods. Interestingly, it is pretty easy to set appropriate parameters for these two methods. Practical experiments show that the proposed methods outperform previous methods in three different circumstances and different noise levels. [ABSTRACT FROM PUBLISHER]

We introduce two new Kirchhoff-law-Johnson-noise (KLJN) secure key distribution schemes which are generalizations of the original KLJN scheme. The first of these, the Random-Resistor (RR-) KLJN scheme, uses random resistors with values chosen from a quasi-continuum set. It is well-known since the creation of the KLJN concept that such a system could work in cryptography, because Alice and Bob can calculate the unknown resistance value from measurements, but the RR-KLJN system has not been addressed in prior publications since it was considered impractical. The reason for discussing it now is the second scheme, the Random Resistor Random Temperature (RRRT-) KLJN key exchange, inspired by a recent paper of Vadai, Mingesz and Gingl, wherein security was shown to be maintained at non-zero power flow. In the RRRT-KLJN secure key exchange scheme, both the resistances and their temperatures are continuum random variables. We prove that the security of the RRRT-KLJN scheme can prevail at a non-zero power flow, and thus the physical law guaranteeing security is not the Second Law of Thermodynamics but the Fluctuation-Dissipation Theorem. Alice and Bob know their own resistances and temperatures and can calculate the resistance and temperature values at the other end of the communication channel from measured voltage, current and power-flow data in the wire. However, Eve cannot determine these values because, for her, there are four unknown quantities while she can set up only three equations. The RRRT-KLJN scheme has several advantages and makes all former attacks on the KLJN scheme invalid or incomplete. [ABSTRACT FROM AUTHOR]

The SRM (Spatial Rich Model) is a very effective steganalysis method. It uses statistics of neighboring noise residual samples as features to capture the dependency changes caused by embedding. Because the noise residuals are the high-frequency components of image and closely tied to image content, the residuals of different types of image regions have different statistical properties and effectiveness for steganalysis. In this paper, the effectiveness of the residuals is investigated. Then the effectiveness of the statistics collected from different types of neighboring residual samples is investigated from the FLD (Fisher Linear Discriminant) viewpoint, and ineffective, effective and high-effective neighboring residual samples are defined. The ineffective neighboring residual samples are not likely to change during embedding, and if they are counted in statistics, they may mix the features with noise and make the features impure. Pure SRM features are extracted based on neighboring noise residual sample selection strategy. Furthermore, multi-order statistical features are proposed to increase the statistical diversity. Steganalysis performances of the statistical features collected from different types of neighboring residual samples are investigated on three content adaptive steganographic algorithms. Experimental results demonstrate that the proposed method can achieve a more accurate detection than SRM. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation of a key distribution protocol over public channels. This protocol has its own source of randomness, based on data from civil air traffic. An equivalent protocol scheme has been developed according to the theoretical protocol, "satellite scenario". Both parties to generate symmetric keys without preshared secrets have been allowed. Keys generated in this way can be used with symmetric encryption (AES, DES). The performance of the proposed protocol has been conducted with rigorous theoretical information analysis. [ABSTRACT FROM AUTHOR]

Communication anonymity is becoming an increasingly important, or even indispensable, security requirement for many applications. The existing research in anonymous communications can largely be divided into two categories: mix-based systems and secure multiparty computation-based systems, originating from mixnet and DC-net, respectively. However, they either cannot provide provable anonymity or suffer from transmission collision problem. In this paper, we first propose a novel unconditionally secure source anonymous message authentication code that can be applied to any messages without relying on any trusted third parties. While ensuring message sender anonymity, secure source anonymous message authentication code can also provide message content authenticity. We then propose a novel communication protocol that can hide the senders and the recipients from each other and thus can be used for secure file sharing. The security analysis demonstrates that the proposed protocol is secure against various attacks. Our analysis also shows that it is efficient and practical. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Threshold public-key encryption can control decryption abilities of an authorized user group in such a way that each user of the group can produce only a decryption share and at least t of them should collect decryption shares to recover a message. We present a new threshold public-key encryption that is secure against selectively chosen ciphertext attacks. Semantic security against chosen ciphertext adversaries is the de facto level of security for public-key encryption deployed in practice because many encryption systems are broken in a model of chosen ciphertext security. The security of the proposed system is formally proved without random oracles under a new assumption. We also provide proof of the intractability of our assumption in the generic group model. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

PRESENT and MIBS are two lightweight block ciphers that are suitable for low resource devices such as radio-frequency identification tags. In this paper, we present the first biclique cryptanalysis of MIBS block cipher and a new biclique cryptanalysis of PRESENT block cipher. These attacks are performed on full-round MIBS-80 and full-round PRESENT-80. Using matching without matrix technique in the attack on MIBS and choosing a sub-key space of an internal round for key division eventuate to reduce the security of this cipher by 1 bit, while the data complexity of attack is 252 chosen plaintext. The attack on PRESENT-80 has a data complexity of at most 222 chosen plaintext and computational complexity of 279.34 encryption that both complexities are lower than of other cryptanalyses of full-round PRESENT-80 so far. Also, in this paper, we use early abort technique to efficiently filter out wrong keys in matching phase of biclique attack of PRESENT-80. [ABSTRACT FROM AUTHOR]

This paper considers security analysis of the YAK, a public key-based authenticated key agreement protocol. The YAK protocol is a variant of the two-pass HMQV protocol but uses zero-knowledge proofs for proving knowledge of ephemeral values. In this paper, we show that the YAK protocol lacks joint key control and perfect forward secrecy attributes and is vulnerable to some attacks including unknown key-share and key-replication attacks. This invalidates the semantic security of the protocol in several security models. There are also other considerations regarding the impersonation and small subgroup attacks. [ABSTRACT FROM AUTHOR]

The development history ofUmkehrwalze Dora, Enigma's pluggable reflector, is presented from the first ideas in the mid-1920s to the last development plans and its actual usage in 1945. An Enigma message in three parts, enciphered withUmkehrwalze Doraand intercepted by the British on 11 March 1945, is shown. The successful recovery of the key of this message is described. Modern computer-based cryptanalysis is used to recover the wiring of the unknown “Uncle Dick,” which the British called this field-rewirable reflector. The attack is based on the known ciphertext and plaintext pair from the first part of the intercept. After recovery of the unknown reflector wiring and the daily key, the plaintext of the second part of the message is revealed. [ABSTRACT FROM PUBLISHER]