Cloud storage can provide a way to effectively store and manage big data. However, due to the separation of data ownership and management, it is difficult for users to check the integrity of data in a traditional way, which leads to the introduction of the auditing techniques. This paper proposes a public auditing protocol with a self-certified public key system using blockchain technology. The user's operational information and metadata information of the file are formed to a block after verified by the checked nodes and then to be put into the blockchain. The chain structure of the block ensures the security of auditing data source. The security analysis shows that attackers can neither derive user’s secret key nor derive users’ data from the collected auditing information in the presented scheme. Furthermore, it can effectively resist against not only the signature forging attacks but also the proof forging attacks. Compared with other public auditing schemes, our scheme based on the self-certified public key system has been improved in storage overhead, communication bandwidth, and verification efficiency.

Location‐based services (LBS) have become an important research area with the rapid development of mobile Internet technology, GPS positioning technology, and the widespread application of smart phones and social networks. LBS can provide convenience and flexibility for the users’ daily life, but at the same time, it also brings security risks to the users’ privacy. Untrusted or malicious LBS servers can collect users’ location data through various ways and disclose it to the third party, thus causing users’ privacy leakage. In this paper, a differential privacy location protection method based on the Markov model for user’s location privacy is proposed. Firstly, the transition probability matrix between states of the n‐order Markov model is used to predict the occurrence state and development trend of events; thereby, the user’s location is predicted, and then a location prediction algorithm based on the Markov model (LPAM) is proposed. Secondly, a location protection algorithm based on differential privacy (LPADP) is proposed, in which location privacy tree (LPT) is constructed according to the location data and the difficulty of retrieval, the two nodes with the largest predicted value of LPT are allocated with a reasonable privacy budget, and Laplace noise is added to protect location privacy. Theoretical analysis and experimental results show that the proposed method not only meets the requirements of differential privacy and protects location privacy effectively but also has high data availability and low time complexity.

White‐box cryptography protects cryptographic software in a white‐box attack context (WBAC), where the dynamic execution of the cryptographic software is under full control of an adversary. Protecting AES in the white‐box setting attracted many scientists and engineers, and several solutions emerged. However, almost all these solutions have been badly broken by various efficient white‐box attacks, which target compositions of key‐embedding lookup tables. In 2014, Luo, Lai, and You proposed a new WBAC‐oriented AES implementation, and claimed that their implementation is secure against both Billet et al . 's attack and De Mulder et al . 's attack. In this study, based on the existing table‐composition‐targeting cryptanalysis techniques, the authors show that the secret key of the Luo–Lai–You (LLY) implementation can be recovered with a time complexity of about 2 44 . Furthermore, the authors propose a new white‐box AES implementation based on table lookups, which is shown to be resistant against the existing table‐composition‐targeting white‐box attacks. The authors, key‐embedding tables are obfuscated with large affine mappings, which cannot be cancelled out by table compositions of the existing cryptanalysis techniques. Although their implementation requires twice as much memory as the LLY WBAES to store the tables, its speed is about 63 times of the latter.

This paper is composed of two main parts related to the nonlinearity of vectorial functions. The first part is devoted to maximally nonlinear (n, m) functions (the so-called bent vectorial functions), which contribute to an optimal resistance to both linear and differential attacks on symmetric cryptosystems. They can be used in block ciphers at the cost of additional diffusion/compression/expansion layers, or as building blocks for the construction of substitution boxes (S-boxes), and they are also useful for constructing robust codes and algebraic manipulation detection codes. A main issue on bent vectorial functions is to characterize bent monomial functions Trmn(λxd) from F2nto F2m(where m is a divisor of n) leading to a classification of those bent monomials. We also treat the case of functions with multiple trace terms involving general results and explicit constructions. Furthermore, we investigate some open problems raised by Pasalic et al. and Muratovic-Ribic et al. in a series of papers on vectorial functions. The second part is devoted to the nonlinearity of (n, m)-functions. No tight upper bound is known when n/2 <; m <; n. The covering radius bound is the only known upper bound in this range (the Sidelnikov- Chabaud-Vaudenay bound coincides with it when m = n - 1 and it has no sense when m <; n - 1). Finding better bounds is an open problem since the 1990s. Moreover, no bound has been found during the last 23 years, which improve upon the covering radius bound for a large part of (n, m)-functions. We derive such upper bounds for functions, which are sufficiently unbalanced or which satisfy some conditions. These upper bounds imply some necessary conditions for vectorial functions to have large nonlinearity.

Summary The major weakness of address space layout randomization is the address space of the program being randomized only once at loading. Therefore, it cannot prevent those advanced code reuse attacks, such as just‐in‐time return‐oriented programming. In view of this situation, we propose an instantaneous and continual address space rerandomization approach, called just‐in‐time address space rerandomization (JIT‐ASR) to thwart the attack. The JIT‐ASR uses the virtual memory management and can ceaselessly change the program's address space by modifying the virtual page number of the code address and page table at runtime. In this way, the address space of the program will change continually. This mechanism will make the addresses used by the attacker become stale, and the attack payload cannot be performed successfully. To demonstrate the effectiveness and efficiency of JIT‐ASR, we apply it to SPEC CPU2006 benchmark suite. The evaluation results and security analysis show that JIT‐ASR can resist the code reuse attacks, especially just‐in‐time return‐oriented programming, and yield low runtime performance overhead (1.2% on average on the SPEC CPU2006 benchmark).

White-box cryptography aims at implementing a cipher to protect its key from being extracted in an untrusted environment, where the attacker has full access to the execution of the cryptographic software. In 2002, Chow et al. proposed the original white-box implementation of AES. Afterwards, various white-box implementations were presented. However, they were all badly broken because of a weakness of the implemented cryptographic algorithms: every parameter of the cryptographic operations is fixed except the round keys. In this paper, we present an AES-like cipher based on key-dependent S-boxes. The new cipher is designed to meet the design criteria of AES and hence provides a security level comparable to AES to resist black-box attacks. Moreover, we present a white-box implementation for our AES-like cipher, which is sufficient to withstand existing white-box attacks.

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.

The r-th order nonlinearity of Boolean functions is an important cryptographic criterion associated with some attacks on stream and block ciphers. It is also very useful in coding theory, since it is related to the covering radii of Reed-Muller codes. In this paper we investigate the lower bound of the higher-order nonlinearity of Niho Boolean functions f(x) = tr(λx d ) over F 2 n , where $\lambda \isin F_2_n^*$, $d = 2^{(n-1)/2} + 2^{(n-1)/4} - 1$ when n = 1 mod 4 or $d = 2^{(n-1)/2} + 2^{(3n-1)/4} - 1$ when n = 3 mod 4.

Privacy and efficiency are two important but seemingly contradictory objectives in radio‐frequency identification (RFID) systems. On one hand, RFID aims to identify objects easily and quickly, on the other hand, users want to maintain the necessary privacy without being tracked down for where they are and what they are doing. Common RFID privacy‐preserving authentication protocols can be classified into tree‐based schemes and group‐based schemes, and all these schemes do not meet the dual goals of efficiency and security at the same time. In 2013, Sakai et al . proposed a randomised skip lists‐based authentication protocol (RSLA), and claimed that the RSLA can resist compromise attacks. In this study, the authors analyse the compromise attacks on RSLA and show that there is no obvious advantage with respect to the privacy of the RSLA compared with balanced tree‐based schemes. Moreover, it is reasonable to claim that protocols based on skip lists are also vulnerable to compromise attacks.

In Eurocrypt 2009, Wu et al. introduced the notion of asymmetric group key agreement ASGKA and presented a generic construction of ASGKA protocols with one communication round. Most of ASGKA protocols are designed under that generic construction. In asymmetric group key agreement protocols, users obtain different decryption keys. Any subset of group members may collude to construct pirate decryption keys, which are different from those of colluders but can correctly decrypt ciphertexts. If a pirate decryption box is found, it is possible to find traitors since their decryption keys are related to their identities. In this paper, a collusion attack on the generic construction of ASGKA by Wu et al. is proposed. It is formally proved that each of colluders participating in the proposed collusion attack is unable to be traced. The attack is additionally applied to a concrete protocol to exemplify the collusion attack. Copyright © 2014 John Wiley & Sons, Ltd.

A visual cryptography scheme (VCS) is a kind of secret sharing scheme which allows the encoding of a secret image intonshares distributed tonparticipants. The beauty of such a scheme is that a set of qualified participants is able to recover the secret image without any cryptographic knowledge and computation devices. An extended visual cryptography scheme (EVCS) is a kind of VCS which consists of meaningful shares (compared to the random shares of traditional VCS). In this paper, we propose a construction of EVCS which is realized by embedding random shares into meaningful covering shares, and we call it the embedded EVCS. Experimental results compare some of the well-known EVCSs proposed in recent years systematically, and show that the proposed embedded EVCS has competitive visual quality compared with many of the well-known EVCSs in the literature. In addition, it has many specific advantages against these well-known EVCSs, respectively.

In this paper we correct the wrong proof of Lemma 7 of the above titled paper (ibid., vol. 52, no. 2, pp. 738-743, Feb. 06), which is very important to the proof of Theorem 8 of the same paper.

Internet voting systems, catering to different requirements, have been widely implemented and used. Some have been successful, while others have experienced unexpected problems. This paper overviews the concerns of using Internet voting and tries to give solutions. Tradeoffs between the advantages and disadvantages of employing Internet voting are also addressed. A simple protocol is designed to show that technical problems identified in the literature can be solved fairly easily, though some seem subtle. This study reveals that the main concerns of adopting Internet voting for critical elections are not cryptographic tools, but hardware and software reliability, and social and political issues. After discussing possible concerns about Internet voting and possible solutions or comments, we propose steps to enable Internet voting to be adopted even for critical elections.