With the growth of public demand for online access to health services, many efforts have been devoted to personal health records (PHR) in cloud computing. It enables patients to manage their personal health information (PHI) in cloud servers, which greatly facilitates the collection, access and sharing of PHI. Since cloud servers are not fully trusted, it is desirable that the PHI can be encrypted for privacy protection before uploaded to the cloud. Besides the privacy of PHI, fine-grained and flexible search control is also strongly desired for a secure PHR system. In this article, we first present attribute set based keyword search (ASBKS) which can realize fine-grained keyword search of encrypted PHR. Compared with the existing searchable encryption with access control, the proposed ASBKS can achieve more flexibility in user attributes organization and more efficiency in specifying policies. Furthermore, we present a hierarchical ASBKS scheme to improve scalability by extending ASBKS with a hierarchical structure of users. We implement our ASBKS scheme and the experimental results demonstrate that it is both efficient and flexible for encrypted PHR in cloud computing.

Providing appropriate monetary rewards is an efficient way for mobile crowdsensing to motivate the participation of task participants. However, a monetary incentive mechanism is generally challenging to prevent malicious task participants and a dishonest task requester. Moreover, prior quality-aware incentive schemes are usually failed to preserve the privacy of task participants. Meanwhile, most existing privacy-preserving incentive schemes ignore the data quality of task participants. To tackle these issues, we propose a privacy-preserving and data quality-aware incentive scheme, called PACE. In particular, data quality consists of the reliability and deviation of data. Specifically, we first propose a zero-knowledge model of data reliability estimation that can protect data privacy while assessing data reliability. Then, we quantify the data quality based on the deviation between reliable data and the ground truth. Finally, we distribute monetary rewards to task participants according to their data quality. To demonstrate the effectiveness and efficiency of PACE, we evaluate it in a real-world dataset. The evaluation and analysis results show that PACE can prevent malicious behaviors of task participants and a task requester, and achieves both privacy-preserving and data quality measurement of task participants.

The minimum travel distance of task participants is one of the significant optimization objectives of privacy-preserving task assignment in mobile crowdsensing (MCS). However, when the travel distance is minimized, most of the previous schemes only focus on the task participant privacy and disregard the task requester privacy. Moreover, existing solutions usually only support the constraint of a single type, such as equality constraints or range constraints. In this paper, we propose a bilateral privacy-preserving Task Assignment mechanism for MCS (iTAM), which protects not only the task participants privacy but also the task requesters privacy and can minimize the travel distance. Furthermore, iTAM provides both equality and range constraints of task assignment by utilizing the Paillier cryptosystem. To accommodate the multiple relations between the task participants and the task, we propose the single/multiple task participants selection problems for a task requiring task participants to compete and cooperate. Experimental evaluations over synthetic and real-world data illustrate that iTAM is feasible and effective. Compared with the state-of-the-art, iTAM positively solves the optimal problem of travel distance. The complexities of iTAM are$\mathcal {O}(n)$and$\mathcal {O}(n\log n)$for a single and multiple task participants selection problems, respectively.

With the outbreak of e-mail message leakage events, such as the Hillary Clinton’s Email Controversy, privacy and security of sensitive e-mail information have become users’ primary concern. Encrypted email seems to be a viable solution for providing security, but it will greatly limit their operations. Public encryption with keyword search (PEKS) scheme is a popular technology to incorporate security protection and favorable operability functions together, which can play an important role in searching over encrypted email in a cloud server. In this paper, we propose a practical PEKS scheme named as public-key multi-keyword searchable encryption with hidden structures (PMSEHS). It could enable e-mail receivers to do the multi-keyword and boolean search in the large encrypted email database as fast as possible, without revealing more information to the cloud server. We also give comparative experiments, which demonstrate that our scheme has a higher efficiency in multi-keyword search for encrypted emails.

Contrast enhancement (CE) of medical images is helpful to bring out the unclear content in the interested regions. Recently, reversible CE has been proposed so that the original version of a contrast‐changed image can be exactly recovered. This property can be used to save storage space or facilitate the archiving system. To enhance the regions of interest (ROI) without introducing visual distortions, the technique of image segmentation (e.g. using Otsu's method) has been used to obtain the background before conducting the CE process. To segment the ROI more accurately, an interactive algorithm called GrabCut is employed in the proposed scheme. In addition, a new preprocessing strategy is adopted to preserve the image quality through the CE process. Consequently, the content in the selected regions can be better brought out while the reversibility of the CE process is achieved. The experimental results on 30 chest radiograph images and 20 magnetic resonance images have demonstrated the efficacy of the proposed scheme for reversible CE. The evaluation results are provided to show the better performances of the proposed method in achieving CE effects and preserving image quality.

A reliable mobile crowdsensing (MCS) application usually relies on sufficient participants and trustworthy data. However, privacy concerns reduce participants' willingness to participate in sensing tasks. The uncertainty of participant behavior and heterogeneity of sensing devices result in the unreliability of sensing data and further bring unreliable MCS services. Hence, it is crucial to estimate the reliability of sensing data and protect privacy. Unfortunately, most existing privacy-preserving data estimation solutions are designed for single-type data. In practice, however, heterogeneous sensing data are ubiquitous in data integration tasks. To this end, we propose a privacy-preserving reliability estimation solution of heterogeneous data for MCS, called IronM, which is effective for text, number, and multimedia data (e.g., image, audio, and video). Specifically, IronM first formulates the reliability assessment of text, number, and multimedia data as equality and range constraints, and then estimates the reliability of heterogeneous data through our proposed privacy-preserving hybrid constraints assessment mechanism. Privacy analysis demonstrates that IronM can not only evaluate the reliability of heterogeneous data but also protect data confidentiality. The experimental results in real-world datasets show the effectiveness and efficiency of IronM.

Reversible data hiding (RDH) can be used to imperceptibly embed data into images in a reversible manner. Many RDH schemes have been developed for uncompressed images. However, JPEG compressed images are more widely used in our daily lives. The existing RDH techniques for JPEG images may cause significant distortion or a large increase in the file size of marked images. In this paper, a novel RDH scheme for JPEG images is proposed. First, the negative influence models of data embedding, including image visual distortion model and file size change model, are mathematically established. Then, a negative index for each frequency is defined as the weighted sum of the normalized average image visual distortion and the normalized average file size change per 1-bit hidden data, and the frequencies with small negative indices will be used for data embedding with a high priority. The weighting factor can be adjusted according to the user's preference for less image distortion or smaller file size. Lastly, secret data is embedded into non-zero quantized AC coefficients of the selected frequencies in ascending order of zero-run length. Extensive experiments conducted on typical images and a well-known image database show that the presented negative influence models are effective, and the proposed RDH scheme based on the models can achieve low image distortion and small increase in the file size of marked images.

Recently, more and more data have been stored in the cloud with keyword indices so that the data users can make search over the databases. In some of these database applications, the query frequency analysis of keywords is quite important to the optimization of the databases and it is easy to be implemented when the data are not encrypted. However, with the growing demands of data privacy, it is desired that the data should be encrypted before uploaded to the cloud. Searchable encryption has been proposed which enables users to make keyword search over the encrypted data with keyword privacy. In a secure searchable encryption scheme, it is required that the keyword in each query should not be revealed. So it becomes challenging to analyze the query frequency of keywords in an encrypted database which has the pressing need of optimization. In this paper, we first consider this problem and present an efficient solution to it which enables the query frequency analysis of keywords without destroying the privacy of the encrypted data and the identity privacy of data users. We also simulate our solution and show that it is practical to the real applications.

As cloud storage becomes more common, concerns about the invasion of privacy are increasing. When images are stored in an encrypted form in the public cloud, reversible data hiding in the encrypted domain can be applied to embed additional data within the encrypted images for ease of management. Most existing works focus on uncompressed images and are not applicable to JPEG images, which are widely used throughout the Internet. Therefore, in this paper, a novel reversible data hiding scheme for encrypted JPEG bitstreams is proposed. First, an effective method of bitstream-based JPEG image encryption is employed to encrypt plaintext JPEG images. Then, we present a reversible data hiding technique for encrypted JPEG images based on invariant zero-run length in the zero-run value pairs. In the cloud, additional data, such as labels, timestamps, origins, and authentication messages, are directly embedded into the encrypted JPEG images with our proposed data hiding technique. From the marked encrypted JPEG images, the extraction of the hidden data and the recovery of the original images can be done independently. Extensive experiments performed on several typical images and three well-known image databases show that the proposed scheme can achieve much higher embedding capacity than that of most recent schemes, and the file sizes of the marked encrypted JPEG images are well preserved compared to those of the related methods. In addition, we provide further analysis to show that the proposed scheme has good format compatibility and low computational complexity.

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.

It has been an active research issue for many years to construct new bent functions. Fork odd with gcd(n, k) = 1 and a ∈ F3n*, the function f (x) = Tr1n(ax((3k+1)/2)) is weakly regular bent over F3n, where Tr1n(·) is the trace function from F3nto F3. This is the well-known Coulter-Matthews bent function. In this paper, we determine the dual function of f (x) completely. As a consequence, we find many classes of ternary bent functions not reported in the literature previously. Such bent functions √ are not quadratic if k > 1 and have (((1 + 5)/2)w+1- ((1 - √5)/2)w+1)/√5 or (((1 +√5)/2)n-w+1- ((1 - √5)/2)n-w+1)/√5 trace terms, where 0n- ((1 - 5)/2)n)/ 5; 2) for the case of k = (n + 1)/2, the number of trace terms is (((1 + 5)/2)n-1- ((1 - 5)/2)n-1)/ 5; 3) for the case of k = (n - 1)/2, the number of trace terms is (((1 + √5)/2)n-1- ((1 - √5)/2)n-1)/√5; 4) for the case of (n, k) = (5t + 4, 4t + 3) or (5t + 1, 4t + 1) with t ≥ 1, the number of trace terms is 8; and 5) for the case of (n, k) = (7t +6, 6t +5) or (7t +1, 6t +1) with t ≥ 1, the number of trace terms is 21. As a byproduct, we find new classes of ternary bent functions with only 8 or 21 trace terms.

Image encryption techniques can be used to ensure the security and privacy of valuable images. The related works in this field have focused more on raster images than on compressed images. Many existing JPEG image encryption schemes are not quite well compatible with the JPEG standard, or the file size of an encrypted JPEG image is apparently increased. In this paper, a novel bitstream-based JPEG image encryption method is presented. First, the groups of successive DC codes that encode the quantized DC coefficient differences with the same sign are permuted within each group. Second, the left half and the right half of a group, whose size will increase with the number of iterations, of consecutive DC codes may be swapped with each other, depending on whether an overflow of quantized DC coefficients occurs during decoding. Third, all AC codes are classified into 63 categories according to their zero-run lengths, then the AC codes within each category are, respectively, scrambled. Finally, all MCUs, except for DC codes, are randomly shuffled as a whole. Moreover, an image-content-related encryption key is employed to provide further security. The experimental results show that the file size of an encrypted JPEG image is almost the same as that of the corresponding plaintext image except for slight variations because of byte alignment. In addition, the quantized DC coefficients decoded from an encrypted JPEG image will not fall outside the valid range. Improved format compatibility is provided compared with other related methods. Moreover, it is unnecessary to perform entropy encoding again because all of the encryption operations are performed directly on the JPEG bitstream. The proposed method proves to be secure against brute-force attacks, differential cryptanalysis, known plaintext attacks, and outline attacks. Our proposed method can also be applied to color JPEG images.

Provable data possession (PDP) allows a user to outsource data with a guarantee that the integrity can be efficiently verified. Existing publicly verifiable PDP schemes require the user to perform expensive computations, such as modular exponentiations for processing data before outsourcing to the storage server, which is not desirable for weak users with limited computation resources. In this paper, we introduce and formalize an online/offline PDP (OOPDP) model, which divides the data processing procedure into offline and online phases. In OOPDP, most of the expensive computations for processing data are performed in the offline phase, and the online phase requires only lightweight computations like modular multiplications. We present a general OOPDP transformation framework which is applicable to PDP-related schemes with metadata aggregatability and public metadata expansibility. Following the framework, we present two efficient OOPDP instantiations. Technically, we present aggregatable vector Chemeleon hash functions which map a vector of values to a group element and play a central role in the OOPDP transformation. Theoretical and experimental analyses confirm that our technique is practical to speed-up PDP schemes.

In cloud computing, computationally weak users are always willing to outsource costly computations to a cloud, and at the same time they need to check the correctness of the result provided by the cloud. Such activities motivate the occurrence of verifiable computation (VC). Recently, Parno, Raykova and Vaikuntanathan showed any VC protocol can be constructed from an attribute-based encryption (ABE) scheme for a same class of functions. In this paper, we propose two practical and efficient semi-adaptively secure key-policy attribute-based encryption (KP-ABE) schemes with constant-size ciphertexts. The semi-adaptive security requires that the adversary designates the challenge attribute set after it receives public parameters but before it issues any secret key query, which is stronger than selective security guarantee. Our first construction deals with small universe while the second one supports large universe. Both constructions employ the technique underlying the prime-order instantiation of nested dual system groups, which are based on the $d$-linear assumption including SXDH and DLIN assumptions. In order to evaluate the performance, we implement our ABE schemes using $\textsf{Python}$ language in Charm. Compared with previous KP-ABE schemes with constant-size ciphertexts, our constructions achieve shorter ciphertext and secret key sizes, and require low computation costs, especially under the SXDH assumption.

At present, ‘mixed-type’ multivariate schemes are relatively rare except the Dragon scheme and its variants (Little Dragon Two scheme and Poly-Dragon scheme). However, they are insecure. In this paper, we first define a particular polynomial called Three-color Polynomial (this polynomial has three-class variables, and the form of the associated symmetric matrix of its quadratic part is similar to the ‘three-color model’ in colorimetry. So we call it three-color polynomial), and its corresponding Three-color Map. Based on the three-color map, we then present a mixed multivariate signature scheme named RGB (it means Red–Green–Blue, because the central map of this scheme is a three-color map, and the ‘three-color’ stands for RGB in colorimetry), which is a variant of the Unbalanced Oil–Vinegar (UOV) signature scheme. Compared with UOV, each polynomial of the central map of RGB has more cross-terms among all the variables |$\{Y,Z,T\}$|⁠. The variable |$Y$| has much to do with message values. To a certain degree, the variable |$Y$| stands for the message values. This means that the message values can be more fully mixed with other variable values in the central map, and the adversary is very difficult to forge the signature. Thus, in theory RGB is more secure than UOV. Through detailed analysis, we find that RGB can resist current known algebraic attacks under proper parameters, such as exhaustive search attack, separation attack, MinRank attack and direct attack (other algebraic attacks are inapplicable for RGB). Besides, our experiments show that under choosing the security level of |$2^{80}$|⁠, the signing time of Magma implementation of RGB is 0.046 s on an ordinary Linux-PC with 2.50 GHz, and the signing time of its C implementation is |$\boldsymbol {\sim }$|0.003 s on an 800 MHz machine. The comparisons show that the signing speed of RGB is faster than that of |${\rm Sflash}^{v2}$|⁠, Quartz, UOV, Rainbow and RSA-1024, and is slightly slower than that of ECDSA-163 and NTRUSign-251. Overall, this new scheme can attain very good performance in terms of security and efficiency.

Multivariate cryptographic systems are one of the most popular public key cryptographic systems, since they have the potential to resist quantum computer attacks. Multivariate signatures have few applications where low area is more of a priority since they are much larger than rivest-shamir-adleman and elliptic curves cryptography. In this paper, we propose a very small cryptographic processor for multivariate signatures and enhance our design in three directions. First, we propose a Modular Arithmetic Logic Unit based on composite field representations. Second, we design a small instruction set. Third, we adapt register reuse and time sharing. Via further other minor optimizations and by integrating the major improvement above, our design is implemented on a small Xilinx field programmable logic array and utilizes only 47 flip flops, 155 look up tables and 92 slices. Its small area would present a significant saving, including fitting into a smaller device, e.g. radio frequency identification tag. Our design can generate multivariate signatures with a moderate speed, e.g. Unbalanced Oil–Vinegar Signature, Rainbow and extensions of Tame Transformation Signature, which is sufficient for numerous applications where area usage is more of a priority. Comparison results show that our design is 50% smaller than the smallest available public key cryptographic system.

Inversions in small finite fields are playing a key role in many areas. We present techniques to exploit binary trees for fast inversions in |$GF(2^n)$| and |$GF(p)$| , where |$n$| is a positive integer and |$p$| is a prime number. The non-pipelined versions of our design in |$GF(2^n)$| and |$GF(p)$| have the execution time of |$(n-1)(T_{AND}+T_{XOR})$| and |$\lfloor \log _2p\rfloor (T_{AND}+T_{XOR})$| , where |$T_{AND}$| and |${T_{XOR}}$| are delays of AND and XOR gates, respectively. The pipelined version of our design has a throughput rate of one result per |$T_{AND}$| (or |$T_{XOR}$| ). The latency is the greater value between |$T_{AND}$| and |$T_{XOR}$| . In other words, the time complexities of non-pipelined and pipelined versions are |$O(n)$| (or |$O(log_2p)$| ) and |$O(1)$| , respectively. Experimental results and comparisons show that our design provides significant reductions in both the execution time and time–area product, e.g. the execution time of inversion in |$GF(2^{12})$| is reduced by 73 |$\%$| and time–area product of inversion in |$GF(2^6)$| is reduced by 77 |$\%$| .

Rainbow is an effective multivariate digital signature scheme proposed by Ding and Schmidt. However, a lot of attacks against it have been proposed. To resist all these attacks, designer should be very careful with its choice of parameters. In this study, the authors will propose a new approach to build a secure variant of Rainbow. According to our security analysis, it could resist all the existing attacks against Rainbow and save some memory in the meantime.

Eight years ago, Pei et al . described a matrix public‐key encryption scheme based on the matrix factorisation over a finite field. Recently, Gu and Zheng also proposed a similar scheme based on the non‐abelian factorisation assumption. The security of these schemes is essentially based on a two‐side matrices exponentiation (TSME) problem. In this study, the authors show that the TSME problem is susceptible to a very efficient linearisation equations attack. Regardless of the public key parameters, the authors can easily find an equivalent key only in polynomial time 𝒪(2 n 5 (log n +1)) from the public key alone, and thus it is very practical and can be implemented within less than 1/20 of a second on the recommended system parameters of the schemes.

Abstract KLEIN is a family of block ciphers whose lightweight features are suitable for resource‐constrained devices. However, the original design of KLEIN does not consider the potential attacks by power analysis methods. This paper presents power analysis attacks against an field‐programmable gate array (FPGA) implementation of KLEIN by the authors of KLEIN. The attacking strategy, attacking point, and complexity of our attacks via power analysis against KLEIN are discussed in detail. Besides, the implementation of the attacks is also described, and the experimental data is given. A lot of attacking experiments are launched by this paper; the best method in our experiment is Correlation Power Analysis (CPA) attack that requires only 4000 random plaintexts and 115 s to reveal the 64‐bit key of KLEIN, with the storage complexity nearly 212 and the success probability of attack nearly 100%. Finally, a defensive countermeasure against our attacks is proposed. Copyright © 2017 John Wiley & Sons, Ltd.

Access control is an indispensable security component of cloud computing, and hierarchical access control is of particular interest since in practice one is entitled to different access privileges. This paper presents a hierarchical key assignment scheme based on linear-geometry as the solution of flexible and fine-grained hierarchical access control in cloud computing. In our scheme, the encryption key of each class in the hierarchy is associated with a private vector and a public vector, and the inner product of the private vector of an ancestor class and the public vector of its descendant class can be used to derive the encryption key of that descendant class. The proposed scheme belongs to direct access schemes on hierarchical access control, namely each class at a higher level in the hierarchy can directly derive the encryption key of its descendant class without the need of iterative computation. In addition to this basic hierarchical key derivation, we also give a dynamic key management mechanism to efficiently address potential changes in the hierarchy. Our scheme only needs light computations over finite field and provides strong key indistinguishability under the assumption of pseudorandom functions. Furthermore, the simulation shows that our scheme has an optimized trade-off between computation consumption and storage space.

More and more clients would like to store their data to public cloud servers (PCSs) along with the rapid development of cloud computing. New security problems have to be solved in order to help more clients process their data in public cloud. When the client is restricted to access PCS, he will delegate its proxy to process his data and upload them. On the other hand, remote data integrity checking is also an important security problem in public cloud storage. It makes the clients check whether their outsourced data are kept intact without downloading the whole data. From the security problems, we propose a novel proxy-oriented data uploading and remote data integrity checking model in identity-based public key cryptography: identity-based proxy-oriented data uploading and remote data integrity checking in public cloud (ID-PUIC). We give the formal definition, system model, and security model. Then, a concrete ID-PUIC protocol is designed using the bilinear pairings. The proposed ID-PUIC protocol is provably secure based on the hardness of computational Diffie-Hellman problem. Our ID-PUIC protocol is also efficient and flexible. Based on the original client's authorization, the proposed ID-PUIC protocol can realize private remote data integrity checking, delegated remote data integrity checking, and public remote data integrity checking.

ABSTRACT Designing group key management schemes is a troubled field. In this paper, we review three schemes recently proposed, including Kayam's scheme for groups with hierarchy, Piao's group key management (KM) scheme, Purushothama's group KM schemes. We point out the problems in each scheme. Kayam's scheme is not secure to collusion attack. Piao's group KM scheme is not secure. The hard problem it bases is not really hard, and the way their scheme uses a hard problem is improper. Purushothama's scheme has an unnecessary design that costs lots of resources and does not give an advantage to the security level and dynamic efficiency of it. We also briefly analyze the underlying reasons why these problems emerge and give suggestions on designing. Copyright © 2014 John Wiley & Sons, Ltd.

Data sharing has never been easier with the advances of cloud computing, and an accurate analysis on the shared data provides an array of benefits to both the society and individuals. Data sharing with a large number of participants must take into account several issues, including efficiency, data integrity and privacy of data owner. Ring signature is a promising candidate to construct an anonymous and authentic data sharing system. It allows a data owner to anonymously authenticate his data which can be put into the cloud for storage or analysis purpose. Yet the costly certificate verification in the traditional public key infrastructure (PKI) setting becomes a bottleneck for this solution to be scalable. Identity-based (ID-based) ring signature, which eliminates the process of certificate verification, can be used instead. In this paper, we further enhance the security of ID-based ring signature by providing forward security: If a secret key of any user has been compromised, all previous generated signatures that include this user still remain valid. This property is especially important to any large scale data sharing system, as it is impossible to ask all data owners to re-authenticate their data even if a secret key of one single user has been compromised. We provide a concrete and efficient instantiation of our scheme, prove its security and provide an implementation to show its practicality.

Data deduplication is a technique for eliminating duplicate copies of data, and has been widely used in cloud storage to reduce storage space and upload bandwidth. However, there is only one copy for each file stored in cloud even if such a file is owned by a huge number of users. As a result, deduplication system improves storage utilization while reducing reliability. Furthermore, the challenge of privacy for sensitive data also arises when they are outsourced by users to cloud. Aiming to address the above security challenges, this paper makes the first attempt to formalize the notion of distributed reliable deduplication system. We propose new distributed deduplication systems with higher reliability in which the data chunks are distributed across multiple cloud servers. The security requirements of data confidentiality and tag consistency are also achieved by introducing a deterministic secret sharing scheme in distributed storage systems, instead of using convergent encryption as in previous deduplication systems. Security analysis demonstrates that our deduplication systems are secure in terms of the definitions specified in the proposed security model. As a proof of concept, we implement the proposed systems and demonstrate that the incurred overhead is very limited in realistic environments.

The hierarchical access control scheme based on Chinese Reminder Theorem CRTHACS was supposed to be capable of hiding the hierarchical structure of a group, but Geiselmann et al. showed practical attacks on CRTHACS to reveal the hierarchies it hides. Then, Zou et al. modified it and gave a new CRTHACS to resist those attacks. Nevertheless, we find that the modified version is still defective if it permits changes of structure, that is, the scheme works in a dynamic scenario. In this paper, we describe our attack on the modified version of CRTHACS. We extend the description of the CRTHACS in a more proper form to make it easier for us to look into the problem it has. We find out the key character of the vulnerability, which we name as double-invariance. We generalize our attack in an algebraic form and apply it to a series of hierarchical cryptographic access control schemes that share the same vulnerability with CRTHACS. We also give the countermeasure to fix this vulnerability. Copyright © 2013 John Wiley & Sons, Ltd.

ABSTRACT Rainbow is a very effective multivariate digital signature scheme proposed by J. Ding and D. Schmidt. In this paper, we define any scheme that has basic multilayer Rainbow structure as Rainbow‐like scheme. Then, we propose a way to enhance Rainbow‐like schemes’ security level against MinRank attack. In our construction, we simply turn some of their first layers’ Oil variables into Vinegar variables by adding corresponding quadratic terms. Copyright © 2014 John Wiley & Sons, Ltd.

We study a variant of oblivious transfer, we called timed-release oblivious transfer that permits a sender to restrict when each receiver may open his chosen messages, without learning anything about the receiver's message choices. To achieve this functionality, we import a time server into the protocol that broadcasts a time token periodically and needs neither to interact with the sender nor the receiver. In our generic construction for the protocol, a primitive called verifiably ID-based encrypted blind signature is introduced as a basic building block. We also present a concrete scheme for the protocol's generic construction. Copyright © 2013 John Wiley & Sons, Ltd.

Wireless medical sensor networks (MSNs) are a key enabling technology in e-healthcare that allows the data of a patient's vital body parameters to be collected by the wearable or implantable biosensors. However, the security and privacy protection of the collected data is a major unsolved issue, with challenges coming from the stringent resource constraints of MSN devices, and the high demand for both security/privacy and practicality. In this paper, we propose a lightweight and secure system for MSNs. The system employs hash-chain based key updating mechanism and proxy-protected signature technique to achieve efficient secure transmission and fine-grained data access control. Furthermore, we extend the system to provide backward secrecy and privacy preservation. Our system only requires symmetric-key encryption/decryption and hash operations and is thus suitable for the low-power sensor nodes. This paper also reports the experimental results of the proposed system in a network of resource-limited motes and laptop PCs, which show its efficiency in practice. To the best of our knowledge, this is the first secure data transmission and access control system for MSNs until now.

Secure group communication systems have become increasingly important for many emerging network applications. An efficient and robust group key management approach is indispensable to a secure group communication system. Motivated by the theory of hyper-sphere, this paper presents a new group key management approach with a group controller (GC). In our new design, a hyper-sphere is constructed for a group and each member in the group corresponds to a point on the hyper-sphere, which is called the member's private point. The GC computes the central point of the hyper-sphere, intuitively, whose “distance” from each member's private point is identical. The central point is published such that each member can compute a common group key, using a function by taking each member's private point and the central point of the hyper-sphere as the input. This approach is provably secure under the pseudo-random function (PRF) assumption. Compared with other similar schemes, by both theoretical analysis and experiments, our scheme (1) has significantly reduced memory and computation load for each group member; (2) can efficiently deal with massive membership change with only two re-keying messages, i.e., the central point of the hyper-sphere and a random number; and (3) is efficient and very scalable for large-size groups.

Wireless sensor networks (WSNs) are widely applicable in monitoring and control of environment parameters. It is sometimes necessary to disseminate data through wireless links after they are deployed in order to adjust configuration parameters of sensors or distribute management commands and queries to sensors. Several approaches have been proposed recently for data discovery and dissemination in WSNs. However, they all focus on how to ensure reliability and usually overlook security vulnerabilities. This paper identifies the security vulnerabilities in data discovery and dissemination when used in WSNs. Such vulnerabilities allow an adversary to update a network with undesirable values, erase critical variables, or launch denial-of-service (DoS) attacks. To address these vulnerabilities, this paper presents the design, implementation, and evaluation of a secure, lightweight, and DoS-resistant data discovery and dissemination protocol named SeDrip for WSNs. Our protocol takes into consideration the limited resources of sensor nodes, packet loss and out-of-sequence packet delivery. Also, it can provide instantaneous authentication without packet buffering delay, and tolerate node compromise. Besides the theoretical analysis that demonstrates the security and performance of SeDrip, this paper also reports the experimental evaluation of SeDrip in a network of resource-limited sensor nodes, which shows its efficiency in practice.

In the grid environment, the resource providers should maintain the ultimate authority over their resources, including access authorization and grain scale control. Apparently, the traditional RBAC model will be inappropriate in multi-autonomous domains environment. Focusing on the autonomous, heterogeneous and dynamic features of grid computing, we propose the concept of "Resource Role". We also initiate the dual-role based access control (DRBAC) framework, where the resource role permission mapping is defined in resource domain and user role resource role mapping is negotiated by user domain and resource domain. This framework is simple and works better than the traditional RBAC in multi domains environment

. This paper analyses description-based communication for autonomous agents when it takes place under ideal conditions. By ideal conditions, is meant the following: agents operate in a domain consisting of novel objects but each object has a finite and unique set of basic properties. Agents are able to completely and accurately observe the basic properties of an object. Furthermore, when an agent describes an object, the agent completely and accurately describes the basic properties of the object. Finally, there are no transmission errors in the communication process and an agent that receives a message believes everything it is told. Under these conditions, it is shown that the object recognition problem is identical to the referent identification problem. Further, referent identification failures and object misrecognitions do not occur. Also, agents never acquire false beliefs, and for any object that an agent knows about, its knowledge of the basic properties of the object is complete. Sufficient conditions are stated to infer that a causal reference chain (description forwarding) is well grounded and it is shown that agents operating under the ideal conditions described above satisfy these requirements.