Search

As cloud computing becomes prevalent, more and more data owners are likely to outsource their data to a cloud server. However, to ensure privacy, the data should be encrypted before outsourcing. Symmetric searchable encryption allows users to retrieve keyword over encrypted data without decrypting the data. Many existing schemes that are based on symmetric searchable encryption only support single keyword search, conjunctive keywords search, multiple keywords search, or single phrase search. However, some schemes, i.e., static schemes, only search one phrase in a query request. In this paper, we propose a multi-phrase ranked search over encrypted cloud data, which also supports dynamic update operations, such as adding or deleting files. We used an inverted index to record the locations of keywords and to judge whether the phrase appears. This index can search for keywords efficiently. In order to rank the results and protect the privacy of relevance score, the relevance score evaluation model is used in searching process on client-side. Also, the special construction of the index makes the scheme dynamic. The data owner can update the cloud data at very little cost. Security analyses and extensive experiments were conducted to demonstrate the safety and efficiency of the proposed scheme.

Searchable encryption is an important technique for public cloud storage service to provide user data confidentiality protection and at the same time allow users performing keyword search over their encrypted data. Previous schemes only deal with exact or fuzzy keyword search to correct some spelling errors. In this paper, we propose a new wildcard searchable encryption system to support wildcard keyword queries which has several highly desirable features. First, our system allows multiple keywords search in which any queried keyword may contain zero, one or two wildcards, and a wildcard may appear in any position of a keyword and represent any number of symbols. Second, it supports simultaneous search on multiple data owner's data using only one trapdoor. Third, it provides flexible user authorization and revocation to effectively manage search and decryption privileges. Fourth, it is constructed based on homomorphic encryption rather than Bloom filter and hence completely eliminates the false probability caused by Bloom filter. Finally, it achieves a high level of privacy protection since matching results are unknown to the cloud server in the test phase. The proposed system is thoroughly analyzed and is proved secure. Extensive experimental results indicate that our system is efficient compared with other existing wildcard searchable encryption schemes in the public key setting.

© 2013 IEEE. In medical cloud computing, a patient can remotely outsource her medical data to the cloud server. In this case, only authorized doctors are allowed to access the data since the medical data is highly sensitive. Before outsourcing, the data is commonly encrypted, where the corresponding secret key is sent to authorized doctors. However, performing searches on encrypted medical data is difficult without decryption. In this paper, we propose two Secure and Efficient Dynamic Searchable Symmetric Encryption (SEDSSE) schemes over medical cloud data. First, we utilize the secure k-Nearest Neighbor (kNN) and Attribute-Based Encryption (ABE) techniques to construct a dynamic searchable symmetric encryption scheme, which can achieve forward privacy and backward privacy simultaneously. These tow security properties are vital and very challenging in the area of dynamic searchable symmetric encryption. Then, we propose an enhanced scheme to solve the key sharing problem which widely exists in the kNN based searchable encryption scheme. Compared with existing proposals, our schemes are better in terms of storage, search and updating complexity. Extensive experiments demonstrate the efficiency of our schemes on storage overhead, index building, trapdoor generating and query.

With recent studies in Searchable Symmetric Encryption (SSE), a client can efficiently perform keyword queries over its outsourced data on a remote but untrusted server (e.g., a public cloud), and correctly retrieve associated files without revealing the confidentiality of his/her data. Besides keyword search, many recent schemes also studied range queries on encrypted data, where range search is also one of the most extensively used queries in databases and information retrieval. However, most of these previous works supporting range search are neither efficient nor compatible with existing keyword SSE schemes. In this paper, we propose two range SSE schemes to enable range queries on encrypted data. Both of our schemes are not only efficient, but also highly compatible with existing keyword SSE schemes. Specifically, the search time of our first scheme is extremely efficient when the values in a range query are sparsely presenting in a dataset; while our second design can achieve an optimal token size and significantly save token generation costs. Moreover, we rigorously define and analyze the security of our schemes, and also conduct extensive experiments with a real dataset to demonstrate the performance of our schemes.

Searchable encryption allows a cloud server to conduct keyword search over encrypted data on behalf of the data users without learning the underlying plaintexts. However, most existing searchable encryption schemes only support single or conjunctive keyword search, while a few other schemes that are able to perform expressive keyword search are computationally inefficient since they are built from bilinear pairings over the composite-order groups. In this paper, we propose an expressive public-key searchable encryption scheme in the prime-order groups, which allows keyword search policies (i.e., predicates, access structures) to be expressed in conjunctive, disjunctive or any monotonic Boolean formulas and achieves significant performance improvement over existing schemes. We formally define its security, and prove that it is selectively secure in the standard model. Also, we implement the proposed scheme using a rapid prototyping tool called Charm [37], and conduct several experiments to evaluate it performance. The results demonstrate that our scheme is much more efficient than the ones built over the composite-order groups.

Cloud storage services have become increasingly popular. Because of the importance of privacy, many cloud storage encryption schemes have been proposed to protect data from those who do not have access. All such schemes assumed that cloud storage providers are safe and cannot be hacked; however, in practice, some authorities (i.e., coercers) may force cloud storage providers to reveal user secrets or confidential data on the cloud, thus altogether circumventing storage encryption schemes. In this paper, we present our design for a new cloud storage encryption scheme that enables cloud storage providers to create convincing fake user secrets to protect user privacy. Since coercers cannot tell if obtained secrets are true or not, the cloud storage providers ensure that user privacy is still securely protected.

This paper considers the security problem of outsourcing storage from user devices to the cloud. A secure searchable encryption scheme is presented to enable searching of encrypted user data in the cloud. The scheme simultaneously supports fuzzy keyword searching and matched results ranking, which are two important factors in facilitating practical searchable encryption. A chaotic fuzzy transformation method is proposed to support secure fuzzy keyword indexing, storage and query. A secure posting list is also created to rank the matched results while maintaining the privacy and confidentiality of the user data, and saving the resources of the user mobile devices. Comprehensive tests have been performed and the experimental results show that the proposed scheme is efficient and suitable for a secure searchable cloud storage system.

This letter presents an efficient polar code-based physical layer encryption (PLE) scheme with a short key length in comparison to the conventional symmetric key cryptosystems. By using the properties of polar codes, we consider several efficient techniques to reduce the key length and the computational overhead of the presented PLE scheme. Moreover, the results of the security analyses show that the proposed scheme has a high level of security against conventional attacks on the PLE schemes. In fact, reducing the key length and the computational overhead of the presented PLE scheme has no effect on its security level, which makes it suitable for secure mobile communication devices with limited resources.

To protect receiver privacy, researchers constructed anonymous multireceiver encryption by implanting anonymity in multireceiver encryption. It allows a sender to produce the identical ciphertext for multiple designated receivers. Every designated receiver can decrypt the ciphertext, but does not know who the other designated receivers are. Recently, several anonymous multireceiver identity (ID)-based encryption (AMIBE) schemes were proposed without the utilization of certificates. However, these AMIBE schemes are not efficient because their decryption cost of each receiver grows linearly with the number of the designated receivers. Moreover, all the ID-based cryptographic schemes suffer from the key escrow problem, which has been resolved by using certificateless public key settings. Very recently, Islam et al. proposed an anonymous multireceiver certificateless encryption (AMCLE) scheme. However, the encryption cost of a sender is quadric with the number of designated receivers, whereas the decryption cost of each receiver is linear with the number. In this paper, we propose an efficient AMCLE scheme with constant decryption cost, namely, the required decryption cost of each receiver is independent of the number of receivers. When compared with previously proposed AMIBE and AMCLE schemes, our scheme solves the key escrow problem and improves the efficiency of encryption/decryption significantly as well.

Cryptographic architectures provide different security properties to sensitive usage models. However, unless reliability of architectures is guaranteed, such security properties can be undermined through natural or malicious faults. In this paper, two underlying block ciphers which can be used in authenticated encryption algorithms are considered, i.e., light encryption device and high security and lightweight block ciphers. The former is of the Advanced Encryption Standard type and has been considered area-efficient, while the latter constitutes a Feistel network structure and is suitable for low-complexity and low-power embedded security applications. In this paper, we propose efficient error detection architectures including variants of recomputing with encoded operands and signature-based schemes to detect both transient and permanent faults. Authenticated encryption is applied in cryptography to provide confidentiality, integrity, and authenticity simultaneously to the message sent in a communication channel. In this paper, we show that the proposed schemes are applicable to the case study of simple lightweight CFB for providing authenticated encryption with associated data. The error simulations are performed using Xilinx Integrated Synthesis Environment tool and the results are benchmarked for the Xilinx FPGA family Virtex-7 to assess the reliability capability and efficiency of the proposed architectures.

A new symmetric key image encryption scheme based on hyper-chaotic Lorenz system is proposed. The encryption process and the decryption process are identical in the proposed scheme. They both include two diffusion operations, one plaintext-related scrambling operation and three matrix rotating 180 degrees operations. The hyper-chaotic Lorenz system is employed to generate the secret code streams to encrypt the plain image, and to implement the diffusion process with XOR operation. The plaintext-related scrambling is used in this scheme to make different plain images correspond to different secret code streams even when the secret keys are the same, so that the scheme can fight against the chosen/known plaintext attacks. Simulation results show that the proposed scheme has the merits of high encryption speed, large key space, strong key sensitivity, strong plaintext sensitivity, good statistical properties of cipher-text, and etc., and can be used in practical communications.

Among the applications of the internet and cloud computing, online social network (OSN) is a very popular service. Since a lot of personal information is stored on the OSN platform, privacy protection on such an application has become a critical issue. Apart from this, OSN platforms need advertisement revenue to enable continued operations. However, if the users encrypt their messages, then OSN providers cannot generate accurate advertisement to users. Thus, how to achieve both privacy preserving and accurate advertisement is a worth-discussing issue. Unfortunately, none of the works on OSNs can achieve both privacy preserving and accurate advertisement simultaneously. In view of this, we propose the first multireceiver predicate encryption scheme for OSN platforms. Not only does the proposed scheme protects the users’ privacy but it achieves customized advertisement as well. Compared with other predicate encryptions deployed in OSN platforms, the proposed scheme gains much shorter ciphertext. The semantic security and attribute hiding of the proposed scheme are proved under the standard model.

Lightweight devices such as smart cards and RFID tags have a very limited hardware resource, which could be too weak to cope with asymmetric-key cryptography. It would be desirable if the cryptographic algorithm could be optimized in order to better use hardware resources. In this paper, we demonstrate how identity-based encryption algorithms from bilinear pairing can be optimized so that hardware resources can be saved. We notice that the identity-based encryption algorithms from bilinear pairing in the literature must perform both elliptic curve group operations and multiplicative group operations, which consume a lot of hardware resources. We manage to eliminate the need of multiplicative group operations for encryption. This is a significant discovery since the hardware structure can be simplified for implementing pairing-based cryptography. Our experimental results show that our encryption algorithm saves up to 47 percent memory (27,239 RAM bits) in FPGA implementation.

Wearable devices can be potentially captured or accessed in an unauthorized manner because of their physical nature. In such cases, they are in white-box attack contexts, where the adversary may have total visibility on the implementation of the built-in cryptosystem, with full control over its execution platform. Dealing with white-box attacks on wearable devices is undoubtedly a challenge. To serve as a countermeasure against threats in such contexts, we propose a lightweight encryption scheme to protect the confidentiality of data against white-box attacks. We constructed the scheme’s encryption and decryption algorithms on a substitution-permutation network that consisted of random secret components. Moreover, the encryption algorithm uses random padding that does not need to be correctly decrypted as part of the input. This feature enables non-bijective linear transformations to be used in each encryption round to achieve strong security. The required storage for static data is relatively small and the algorithms perform well on various devices, which indicates that the proposed scheme satisfies the requirements of wearable computing in terms of limited memory and low computational power.

Two-server password-authenticated key exchange allows the client to split a low-entropy password into two pieces and store them in two servers, respectively, and the two servers collaboratively authenticate the client and establish session keys. Even though either server has been corrupted, it guarantees that the password still remains secure. In 2014, Yi et al. proposed a compiler that transforms any two-party PAKE protocol to a two-server PAKE protocol by dint of the ID-based public-key encryption system under the standard model. Moreover, it is claimed that the scheme is provably secure in a relevant formal model. In this letter, we point out an existing related-key attack to their scheme so that when one server is corrupted, the adversary can subtly derive the fresh key shared by the remaining two honest parties. In addition, we suggest a simple patch to avoid this concern.

Ciphertext policy attribute-based encryption (CP-ABE) is a promising cryptographic technique for fine-grained access control of outsourced data in the cloud. However, some drawbacks of key management hinder the popularity of its application. One drawback in urgent need of solution is the key escrow problem. We indicate that front-end devices of clients like smart phones generally have limited privacy protection, so if private keys are entirely held by them, clients risk key exposure that is hardly noticed but inherently existed in previous research. Furthermore, enormous client decryption overhead limits the practical use of ABE. In this paper, we propose a collaborative key management protocol in CP-ABE. Our construction realizes distributed generation, issue and storage of private keys without adding any extra infrastructure. A fine-grained and immediate attribute revocation is provided for key update. The proposed collaborative mechanism effectively solves not only key escrow problem but also key exposure. Meanwhile, it helps markedly reduce client decryption overhead. A comparison with other representative CP-ABE schemes demonstrates that our scheme has somewhat better performance in terms of cloud-based outsourced data sharing on mobile devices. Finally, we provide proof of security for the proposed protocol.

Fog computing is a paradigm that extends cloud computing to the edge of the network. It can provide computation and storage services to end devices in Internet of Things (IoT). Attribute-based cryptography is a well-known technology to guarantee data confidentiality and fine-grained data access control. However, its computational cost in encryption and decryption phase is linear with the complexity of policy. In this paper, we propose a secure and fine-grained data access control scheme with ciphertext update and computation outsourcing in fog computing for IoT. The sensitive data of data owner are first encrypted using attribute-based encryption with multiple policies and then outsourced to cloud storage. Hence, the user whose attributes satisfy the access policy can decrypt the ciphertext. Based on the attribute-based signature technique, authorized user whose attributes integrated in the signature satisfy the update policy can renew the ciphertext. Specifically, most of the encryption, decryption, and signing computations are outsourced from end devices to fog nodes, and thus, the computations for data owners to encrypt, end users to decrypt, re-encrypt, and sign are irrelevant to the number of attributes in the policies. The security analysis shows that the proposed scheme is secure against known attacks, and the experimental results show that the fog nodes perform most of the computation operations of encryption, decryption, and signing, and hence, the time of encryption for data owner, decryption, re-encryption, and signing for users is small and constant.

Since Cloud Service Provider is a semi-trusted party in cloud storage, to protect data from being disclosed, users' data are encrypted before being uploaded to a cloud server. Undoubtedly, flexible encrypted data sharing is a very important demand required by cloud storage users, whereas few schemes have being designed to satisfy this demand. In this paper, based on conditional proxy broadcast re-encryption technology, an encrypted data sharing scheme for secure cloud storage is proposed. The scheme not only achieves broadcast data sharing by taking advantage of broadcast encryption, but also achieves dynamic sharing that enables adding a user to and removing a user from sharing groups dynamically without the need to change encryption public keys. Moreover, by using proxy re-encryption technology, our scheme enables the proxy (cloud server) to directly share encrypted data to the target users without the intervention of data owner while keeping data privacy, so that greatly improves the sharing performance. Meanwhile, the correctness and the security are proved; the performance is analyzed, and the experimental results are shown to verify the feasibility and the efficiency of the proposed scheme.

Designing lightweight security protocols for cloud-based Internet-of-Things (IoT) applications for battery-limited mobile devices, such as smart phones and laptops, is a topic of recent focus. Ciphertext-policy attribute-based encryption (CP-ABE) is a viable solution, particularly for cloud deployment, as an encryptor can “write” the access policy so that only authorized users can decrypt and have access to the data. However, most existing CP-ABE schemes are based on the costly bilinear maps, and require long decryption keys, ciphertexts and incur significant computation costs in the encryption and decryption (e.g. costs is at least linear to the number of attributes involved in the access policy). These design drawbacks prevent the deployment of CP-ABE schemes on battery-limited mobile devices. In this paper, we propose a new RSA-based CP-ABE scheme with constant size secret keys and ciphertexts (CSKC) and has $\mathcal {O}(1)$ time-complexity for each decryption and encryption. Our scheme is then shown to be secure against a chosen-ciphertext adversary, as well as been an efficient solution with the expressive AND gate access structures (in comparison to other related existing schemes). Thus, the proposed scheme is suitable for deployment on battery-limited mobile devices.

Community detection is an important aspect of social network analysis, but social factors such as user intimacy, influence, and user interaction behavior are often overlooked as important factors. Most of the existing methods are single classification algorithms; multi-classification algorithms that can discover overlapping communities are still incomplete. In former works, we calculated intimacy based on the relationship between users, and divided them into their social communities based on intimacy. However, a malicious user can obtain the other user relationships, thus to infer other users interests, and even pretend to be the another user to cheat others. Therefore the information users concerned about needs to be transferred in the manner of privacy protection. In this paper, we propose an efficient privacy preserving algorithm to preserve the privacy of information in social networks. First, during expansion of communities on the base of mining seed, in order to prevent others from malicious users, we verify their identities after they send a request. We make use of the recognition and nontampering of the block chain to store the user's public key and bind to the block address, which is used for authentication. At the same time, in order to prevent the honest but curious users from illegal access to other users' information, we do not send plaintext directly after the authentication, but hash the attributes by mixed hash encryption to make sure that users can only calculate the matching degree rather than know specific information of other users. Analysis shows that our protocol would serve well against different types of attacks.

For users in possession of password-protected encrypted data in persistent storage (i.e., “data at rest”), an obvious problem is that the password may be extracted by an adversary through dictionary attacks, or by coercing the user. Traditional full disk encryption (FDE) or plausibly deniable encryption cannot adequately address such situations. Therefore, making data verifiably inaccessible in a stealthy and quick fashion may be the preferred choice, specifically for users, such as government/corporate agents, journalists, and human rights activists with highly confidential secrets, when caught and interrogated in a hostile territory. Using secure storage on a trusted platform module (TPM) and modern CPU’s trusted execution mode (e.g., Intel TXT), we design Gracewipe to enable secure and verifiable deletion of encryption keys through a special deletion password. When coerced, a user can fake compliance and enter the deletion password; and then, the user can prove to the adversary that Gracewipe has been executed and the real key is no longer available (through a TPM quote), hoping for a favorable situation (e.g., end of torture). To unlock the target encryption key, the adversary can only guess passwords through the valid Gracewipe environment with a high-risk of triggering deletion of the real key. Based on our two primary Gracewipe prototypes (i.e., software-based FDE with TrueCrypt and hardware-based FDE with self-encrypting drive), we also design and implement an extended family of unlocking schemes for triggering deletion, to achieve better plausibility, security and usability. We incur between 2–2.5 seconds delay during boot, and no performance penalty at run-time.

Public key encryption with keyword search (PEKS) is a well-known cryptographic primitive for secure searchable data encryption in cloud storage. Unfortunately, it is inherently subject to the (inside) offline keyword guessing attack (KGA), which is against the data privacy of users. Existing countermeasures for dealing with this security issue mainly suffer from low efficiency and are impractical for real applications. In this paper, we provide a practical and applicable treatment on this security vulnerability by formalizing a new PEKS system named server-aided public key encryption with keyword search (SA-PEKS). In SA-PEKS, to generate the keyword ciphertext/trapdoor, the user needs to query a semitrusted third-party called keyword server (KS) by running an authentication protocol, and hence, security against the offline KGA can be obtained. We then introduce a universal transformation from any PEKS scheme to a secure SA-PEKS scheme using the deterministic blind signature. To illustrate its feasibility, we present the first instantiation of SA-PEKS scheme by utilizing the Full Domain Hash RSA signature and the PEKS scheme proposed by Boneh et al. in Eurocrypt 2004. Finally, we describe how to securely implement the client-KS protocol with a rate-limiting mechanism against online KGA and evaluate the performance of our solutions in experiments.

In a system that performs both encryption and lossy compression, the conventional way is to compress first and then encrypt the compressed data. This separation approach has been proved to be optimal. In certain applications where sensitive information should be protected as early as possible, it is preferable to perform the encryption first and then compress the encrypted data, which leads to the concept of the reversed system. Johnson et al. proposed an achievable scheme for the reversed system, where a modulo-sum encryption is followed by a compression using the Wyner–Ziv distributed source coding with side information. However, in general, this reversed system performs worse than the conventional system in the sense that it requires more compression rate and secrecy key rate. In this paper, we propose a new achievable scheme for the reversed system, where the encryption is conducted by a permutation cipher, and then, the encrypted data is compressed using the optimal rate-distortion code. The proposed scheme can achieve the optimal compression rate and secret key rate. As a result, we show that reversing the order of the encryption and compression does not necessarily compromise the performance of an encryption-compression system. We show that the proposed system attains strong secrecy, and the information leakage vanishes exponentially.

Cloud computing facilitates convenient and on-demand network access to a centralized pool of resources. Currently, many users prefer to outsource data to the cloud in order to mitigate the burden of local storage. However, storing sensitive data on remote servers poses privacy challenges and is currently a source of concern. SE (Searchable Encryption) is a positive way to protect users sensitive data, while preserving search ability on the server side. SE allows the server to search encrypted data without leaking information in plaintext data. The two main branches of SE are SSE (Searchable Symmetric Encryption) and PEKS (Public key Encryption with Keyword Search). SSE allows only private key holders to produce ciphertexts and to create trapdoors for search, whereas PEKS enables a number of users who know the public key to produce ciphertexts but allows only the private key holder to create trapdoors. This article surveys the two main techniques of SE: SSE and PEKS. Different SE schemes are categorized and compared in terms of functionality, efficiency, and security. Moreover, we point out some valuable directions for future work on SE schemes.

Confidentiality and authentication are two main security goals in secure electronic mail (e-mail). Pretty good privacy (PGP) and secure/multipurpose internet mail extensions (S/MIME) are two famous secure e-mail solutions. Both PGP and S/MIME use digital envelope to provide message confidentiality and digital signature to provide message authentication. However, these methods have the following two weaknesses: 1) digital signature provides non-repudiation evidence of sender that is not desired in some e-mail applications and 2) efficiency is low, since these methods use two kinds of public key cryptographic primitives: public key encryption and digital signature. To overcome the above two weaknesses, we introduce a new concept called deniably authenticated encryption that can achieve confidentiality, integrity, and deniable authentication in a logical single step. We first propose a deniably authenticated encryption scheme and prove its security in the random oracle model. Then, we design a secure e-mail protocol using the proposed deniably authenticated encryption scheme. The deniable authentication property protects senders’ privacy.

This paper describes the first constructions of identity-based broadcast encryption (IBBE) using Type-3 pairings, which can be proved secure against adaptive-identity attacks based on the Symmetric eXternal Diffie–Hellman assumption (which is a static, if not a standard, assumption) achieving a security degradation which is not exponential in the size of the target identity set. The constructions are obtained by extending the currently known most efficient identity-based encryption scheme proposed by Jutla and Roy in 2013. The new constructions fill both a practical and a theoretical gap in the literature on efficient IBBE schemes.

A hierarchical key assignment scheme is a method to assign some private information and encryption keys to a set of classes in a partially ordered hierarchy, in such a way that the private information of a higher class can be used to derive the keys of all classes lower down in the hierarchy. Sometimes, it is necessary to make dynamic updates to the hierarchy, in order to implement an access control policy which evolves with time. All security models for hierarchical key assignment schemes have been designed to cope with static hierarchies and do not consider the issue of performing dynamic updates to the hierarchy. In this paper, we define the concept of hierarchical key assignment schemes supporting dynamic updates, formalizing the relative security model. In particular, we provide the notion of security with respect to key indistinguishability, by considering the dynamic changes to the hierarchy. Moreover, we show how to construct a hierarchical key assignment scheme supporting dynamic updates, by using as a building block a symmetric encryption scheme. The proposed construction is provably secure with respect to key indistinguishability, and provides efficient key derivation and updating procedures, while requiring each user to store only a single private key.

Predicate encryption is a public-key encryption that supports attribute-hiding as well as payload-hiding and achieves high flexibility in terms of access control. Since Katz, Sahai, and Waters first proposed the predicate encryption scheme in 2008, several predicate encryption schemes have been published. Unfortunately these are impractical as they require $O(n)$ pairing computations for decryption with considerably large sized public parameters, secret key, and ciphertext, where $n$ is the dimension of the attribute/predicate vectors. In this paper, we propose a very efficient predicate encryption scheme that requires only $n$ exponentiation plus three pairing computations for decryption with shorter sized public parameters, secret key, and ciphertext. The proposed scheme is proven selective attribute-secure against chosen-plaintext attacks in the standard model under the Asymmetric Decisional Bilinear Diffie-Hellman assumptions.

In the field of sequencing of secret number, an important problem is how to establish an efficient and secure protocol for sorting the secret number. As a powerful tool in solving privacy sequencing problems, secure multipart computation is more and more popular in anonymous voting and online auction. In the present study, related secure computation protocol for sequencing problem is not many by far. In order to improve the efficiency and safety, we propose a security sequencing protocol based on homomorphic encryption. We also give analysis of correctness and security to highlight its feasibility.

In this paper, we present a new public key broadcast encryption (BE) for achieving adaptive security against arbitrary number of colluders. Specifically, our scheme is built from composite order multilinear maps and enjoys ciphertext overhead of a constant number of group elements which are ${O}$ (1) bits. Furthermore, the private key size and public key size are all poly-logarithmic in the total number of users. Herein, we generalize the methodology of Lewko and Waters for realizing dual system encryption to the composite order multilinear groups, and then prove the adaptive security of our scheme under static assumptions in the standard model. Compared with the state-of-the-art, our scheme achieves the adaptive security in simple and non-interactive falsifiable assumptions with the optimized parameter size for BE.

In mobile social networks, to guarantee the security and privacy in the friend discovery process, we propose a hierarchical multi-authority and attribute-based encryption (ABE) friend discovery scheme based on ciphertext-policy (CP)-ABE. It employs character attribute subsets to achieve flexible fine-grained access control, which solves the problem of single-point failure and performance bottleneck. Performance analysis demonstrates the superiority of our scheme in terms of system initialization time and key generation time.

In this paper, we revisit the private over-threshold data aggregation problem. We formally define the problem's security requirements as both data and user privacy goals. To achieve both goals, and to strike a balance between efficiency and functionality, we devise an efficient cryptographic construction and its proxy-based variant. Both schemes are provably secure in the semi-honest model. Our key idea for the constructions and their malicious variants is to compose two encryption functions tightly coupled in a way that the two functions are commutative and one public-key encryption has an additive homomorphism. We call that double encryption. We analyze the computational and communication complexities of our construction, and show that it is much more efficient than the existing protocols in the literature. Specifically, our protocol has linear complexity in computation and communication with respect to the number of users. Its round complexity is also linear in the number of users. Finally, we show that our basic protocol is efficiently transformed into a stronger protocol secure in the presence of malicious adversaries, and provide the resulting protocol's performance and security analysis.

The capability of selectively sharing encrypted data with different users via public cloud storage may greatly ease security concerns over inadvertent data leaks in the cloud. A key challenge to designing such encryption schemes lies in the efficient management of encryption keys. The desired flexibility of sharing any group of selected documents with any group of users demands different encryption keys to be used for different documents. However, this also implies the necessity of securely distributing to users a large number of keys for both encryption and search, and those users will have to securely store the received keys, and submit an equally large number of keyword trapdoors to the cloud in order to perform search over the shared data. The implied need for secure communication, storage, and complexity clearly renders the approach impractical. In this paper, we address this practical problem, which is largely neglected in the literature, by proposing the novel concept of key-aggregate searchable encryption and instantiating the concept through a concrete KASE scheme, in which a data owner only needs to distribute a single key to a user for sharing a large number of documents, and the user only needs to submit a single trapdoor to the cloud for querying the shared documents. The security analysis and performance evaluation both confirm that our proposed schemes are provably secure and practically efficient.

Ciphertext-policy attribute-based encryption (CP-ABE) has been a preferred encryption technology to solve the challenging problem of secure data sharing in cloud computing. The shared data files generally have the characteristic of multilevel hierarchy, particularly in the area of healthcare and the military. However, the hierarchy structure of shared files has not been explored in CP-ABE. In this paper, an efficient file hierarchy attribute-based encryption scheme is proposed in cloud computing. The layered access structures are integrated into a single access structure, and then, the hierarchical files are encrypted with the integrated access structure. The ciphertext components related to attributes could be shared by the files. Therefore, both ciphertext storage and time cost of encryption are saved. Moreover, the proposed scheme is proved to be secure under the standard assumption. Experimental simulation shows that the proposed scheme is highly efficient in terms of encryption and decryption. With the number of the files increasing, the advantages of our scheme become more and more conspicuous.

We introduce a new encryption notion called distance-based encryption (DBE) to apply biometrics in identity-based encryption. In this notion, a ciphertext encrypted with a vector and a threshold value can be decrypted with a private key of another vector, if and only if the distance between these two vectors is less than or equal to the threshold value. The adopted distance measurement is called Mahalanobis distance, which is a generalization of Euclidean distance. This novel distance is a useful recognition approach in the pattern recognition and image processing community. The primary application of this new encryption notion is to incorporate biometric identities, such as face, as the public identity in an identity-based encryption. In such an application, usually the input biometric identity associated with a private key will not be exactly the same as the input biometric identity in the encryption phase, even though they are from the same user. The introduced DBE addresses this problem well as the decryption condition does not require identities to be identical but having small distance. The closest encryption notion to DBE is the fuzzy identity-based encryption, but it measures biometric identities using a different distance called an overlap distance (a variant of Hamming distance) that is not widely accepted by the pattern recognition community, due to its long binary representations. In this paper, we study this new encryption notion and its constructions. We show how to generically and efficiently construct such a DBE from an inner product encryption (IPE) with reasonable size of private keys and ciphertexts. We also propose a new IPE scheme with the shortest private key to build DBE, namely, the need for a short private key. Finally, we study the encryption efficiency of DBE by splitting our IPE encryption algorithm into offline and online algorithms.

Broadcast encryption (BE) schemes allow a sender to securely broadcast to any subset of members but require a trusted party to distribute decryption keys. Group key agreement (GKA) protocols enable a group of members to negotiate a common encryption key via open networks so that only the group members can decrypt the ciphertexts encrypted under the shared encryption key, but a sender cannot exclude any particular member from decrypting the ciphertexts. In this paper, we bridge these two notions with a hybrid primitive referred to as contributory broadcast encryption (ConBE). In this new primitive, a group of members negotiate a common public encryption key while each member holds a decryption key. A sender seeing the public group encryption key can limit the decryption to a subset of members of his choice. Following this model, we propose a ConBE scheme with short ciphertexts. The scheme is proven to be fully collusion-resistant under the decision $n$ -Bilinear Diffie-Hellman Exponentiation (BDHE) assumption in the standard model. Of independent interest, we present a new BE scheme that is aggregatable. The aggregatability property is shown to be useful to construct advanced protocols.

Recently, a number of extended Proxy Re-Encryptions (PRE), e.g. Conditional (CPRE), identity-based PRE (IPRE) and broadcast PRE (BPRE), have been proposed for flexible applications. By incorporating CPRE, IPRE and BPRE, this paper proposes a versatile primitive referred to as conditional identity-based broadcast PRE (CIBPRE) and formalizes its semantic security. CIBPRE allows a sender to encrypt a message to multiple receivers by specifying these receivers’ identities, and the sender can delegate a re-encryption key to a proxy so that he can convert the initial ciphertext into a new one to a new set of intended receivers. Moreover, the re-encryption key can be associated with a condition such that only the matching ciphertexts can be re-encrypted, which allows the original sender to enforce access control over his remote ciphertexts in a fine-grained manner. We propose an efficient CIBPRE scheme with provable security. In the instantiated scheme, the initial ciphertext, the re-encrypted ciphertext and the re-encryption key are all in constant size, and the parameters to generate a re-encryption key are independent of the original receivers of any initial ciphertext. Finally, we show an application of our CIBPRE to secure cloud email system advantageous over existing secure email systems based on Pretty Good Privacy protocol or identity-based encryption.

Attribute-based encryption (ABE) has emerged as a promising solution for access control to diverse set of users in cloud computing systems. Policy can just specify whether (or not) any specific user should be given access to data, but it lacks to provide data owner the privilege to specify (how much) fraction, or (which) specific chunk from that data to be accessed or decrypted. In this paper, we address this issue, and propose a scheme that will give data owner excessive access control, so that he can specify specific chunk out of total data to be accessed by user depending on his attributes. In our scheme, a data owner can encrypt data over attributes specified in a policy, but even if user's attributes satisfy the policy; he can decrypt data (partially or fully) fractionally based on his attributes specified by owner. The owner can also prioritize user's access based on his designation, or hierarchal role in a specific organization. We also address to resolve the issue of attributes repetition, due to which the cost of computations in encryption by owner and ciphertext size is reduced. Furthermore, we achieve it with a single ciphertext over policy for entire data, and proof our scheme to be secure in the generic group and random oracle model. Theoretical comparisons of computations with existing constructions, and performance of the scheme evaluated in the Charm simulator is reasonable enough to be adopted in practice.

We propose two new ciphertext policy attribute-based encryption (CP-ABE) schemes where the access policy is defined by AND-gate with wildcard. In the first scheme, we present a new technique that uses only one group element to represent an attribute, while the existing ABE schemes of the same type need to use three different group elements to represent an attribute for the three possible values (namely, positive, negative, and wildcard). Our new technique leads to a new CP-ABE scheme with constant ciphertext size, which, however, cannot hide the access policy used for encryption. The main contribution of this paper is to propose a new CP-ABE scheme with the property of hidden access policy by extending the technique we used in the construction of our first scheme. In particular, we show a way to bridge ABE based on AND-gate with wildcard with inner product encryption and then use the latter to achieve the goal of hidden access policy. We prove that our second scheme is secure under the standard decisional linear and decisional bilinear Diffie-Hellman assumptions.

To leverage the power of cloud computing, you can no longer encrypt data the traditional way. However, anyone (including the cloud service itself) can easily read unencrypted data. Fully homomorphic encryption reconciles this dilemma.

Compression and encryption are widely used in network traffic in order to improve efficiency and security of some systems. We propose a scheme to concatenate both functions and run them in a paralle pipelined fashion, demonstrating both a hardware and a software implementation. With minor modifications to the hardware accelerators, latency can be reduced to half. Furthermore, we also propose a seminal and more efficient scheme, where we integrate the technology of encryption into the compression algorithm. Our new integrated optimization scheme reaches an increase of 1.6X by using parallel software scheme However, the security level of our new scheme is not desirable compare with previous ones. Fortunately, we prove that this does not affect the application of our schemes.

Attribute-based encryption (ABE) is a promising technique for fine-grained access control of encrypted data in a cloud storage, however, decryption involved in the ABEs is usually too expensive for resource-constrained front-end users, which greatly hinders its practical popularity. In order to reduce the decryption overhead for a user to recover the plaintext, Green et al. suggested to outsource the majority of the decryption work without revealing actually data or private keys. To ensure the third-party service honestly computes the outsourced work, Lai et al. provided a requirement of verifiability to the decryption of ABE, but their scheme doubled the size of the underlying ABE ciphertext and the computation costs. Roughly speaking, their main idea is to use a parallel encryption technique, while one of the encryption components is used for the verification purpose. Hence, the bandwidth and the computation cost are doubled. In this paper, we investigate the same problem. In particular, we propose a more efficient and generic construction of ABE with verifiable outsourced decryption based on an attribute-based key encapsulation mechanism, a symmetric-key encryption scheme and a commitment scheme. Then, we prove the security and the verification soundness of our constructed ABE scheme in the standard model. Finally, we instantiate our scheme with concrete building blocks. Compared with Lai et al. ’s scheme, our scheme reduces the bandwidth and the computation costs almost by half.

We show several concrete attacks on an authenticated encryption (AE) scheme PAE, which appeared in the IEEE TRANSACTIONS ON INFORMATION THEORY, vol. 56, no. 8, pp. 4025–4037. In addition, we show some flaws and oversights in the analysis (presented in the same paper) used to prove PAE to be a secure AE scheme.

For ranked search in encrypted cloud data, order preserving encryption (OPE) is an efficient tool to encrypt relevance scores of the inverted index. When using deterministic OPE, the ciphertexts will reveal the distribution of relevance scores. Therefore, Wang et al. proposed a probabilistic OPE, called one-to-many OPE, for applications of searchable encryption, which can flatten the distribution of the plaintexts. In this paper, we proposed a differential attack on one-to-many OPE by exploiting the differences of the ordered ciphertexts. The experimental results show that the cloud server can get a good estimate of the distribution of relevance scores by a differential attack. Furthermore, when having some background information on the outsourced documents, the cloud server can accurately infer the encrypted keywords using the estimated distributions.

Encryptions are used in almost all standards to ensure the confidentiality of the data. Encryptions can be and indeed are implemented in the different layers of a network protocol stack. Conventional encryption performs the bitwise XOR operation between one message bit and one key stream bit to generate one ciphertext bit. Huo et al. have recently proposed to provide confidentialities on the user data by performing the phase encryption on the time domain OFDM samples in LTE system. Phase encryption is performed on the modulated symbols, different from the bit level of XOR encryption, i.e., stream cipher encryption. In this paper, we extend their study. We first generalize the phase encryption to general communication systems independent of the underlying modulation scheme. Then, we formulate the mathematical models for XOR and phase encryptions. Based on our model, we compare these two encryption methods in terms of their security and encryption efficiency. We also show phase encryption can resist traffic analysis attack when implemented in the physical layer. Finally, we conduct simulations to compare the performance of these two methods in terms of their decoding symbol error rate.

A secure reconfigurable cryptographic co-processor supporting multiple algorithms of advanced encryption standard (AES), data encryption standard (DES), rivest cipher 6, and international data encryption algorithm is proposed using its own reconfigurable feature to resist side-channel attack (SCA). It is integrated into a system-on-chip and fabricated in $0.18~\boldsymbol {\mu }\text{m}$ CMOS process with 1.8 V supply voltage and 100 MHz max frequency. Several kinds of specific countermeasures are proposed to hide leakage information by utilizing idle reconfigurable processing elements to do dummy operations. Its advantages lie in its little impact on area and frequency as well as high flexibility after silicon that countermeasures can also be reconfigured. Furthermore, different protections including several kinds of global countermeasures and encryption flow related countermeasures can be stacked, thus the security level can be tuned by trading for some performance or power consumption. Experimental SCA attack results show that it resists simple power analysis and differential power analysis without revealing the subkey. For correlation-based electromagnetic analysis (EMA) of DES configuration, it increases $36\boldsymbol {\times } $ measure to disclosure when applied with partial countermeasures compared to unprotected DES. As to AES configuration with full countermeasures, it resists EMA with no sign to reveal the right subkey for up to 1.2 million electromagnetic traces.

In cloud, data access control is a crucial way to ensure data security. Functional encryption (FE) is a novel cryptographic primitive supporting fine-grained access control of encrypted data in cloud. In FE, every ciphertext is specified with an access policy, a decryptor can access the data if and only if his secret key matches with the access policy. However, the FE cannot be directly applied to construct access control scheme due to the exposure of the access policy which may contain sensitive information. In this paper, we deal with the policy privacy issue and present a mechanism named multi-authority vector policy (MAVP) which provides hidden and expressive access policy for FE. Firstly, each access policy is encoded as a matrix and decryptors can only obtain the matched result from the matrix in MAVP. Then, we design a novel function encryption scheme based on the multi-authority spatial policy (MAVPFE), which can support privacy-preserving yet non-monotone access policy. Moreover, we greatly improve the efficiency of encryption and decryption in MAVP-FE by shifting the major computation of clients to the outsourced server. Finally, the security and performance analysis show that our MAVP-FE is secure and efficient in practice.

Over the past decade, the application domain of wireless sensor networks has expanded steadily, ranging from environmental management to industry control, and from structural health monitoring to strategic surveillance. With the proliferation of sensor networks at home, work place, and beyond, securing data in the network has become a challenge. A number of security mechanisms have been proposed for sensor networks to provide data confidentiality: 1) advanced encryption system; 2) KATAN; 3) LED; and 4) TWINE. However, these schemes have drawbacks, including security vulnerabilities, need for hardware-based implementation, and higher computational complexity. To address these limitations, we propose a lightweight block cipher based on chaotic map and genetic operations. The proposed cryptographic scheme employs elliptic curve points to verify the communicating nodes and as one of the chaotic map parameters to generate the pseudorandom bit sequence. This sequence is used in XOR, mutation, and crossover operations in order to encrypt the data blocks. The experimental results based on Mica2 sensor mote show that the proposed encryption scheme is nine times faster than the LED protocol and two times faster than the TWINE protocol. We have also performed a number of statistical tests and cryptanalytic attacks to evaluate the security strength of the algorithm and found the cipher provably secure.

We introduce a hybrid homomorphic encryption that combines public-key encryption (PKE) and somewhat homomorphic encryption (SHE) to reduce the storage requirements of most somewhat or fully homomorphic encryption (FHE) applications. In this model, messages are encrypted with a PKE and computations on encrypted data are carried out using SHE or FHE after homomorphic decryption. To obtain efficient homomorphic decryption, our hybrid scheme combines IND-CPA PKE without complicated message padding with SHE with a large integer message space. Furthermore, if the underlying PKE is multiplicative, the proposed scheme has the advantage that polynomials of arbitrary degree can be evaluated without bootstrapping. We construct this scheme by concatenating the ElGamal and Goldwasser–Micali schemes over a ring $ {\mathbb Z}_{N}$ for a composite integer $N$ whose message space is $ {\mathbb Z}_{N}^\times \vphantom {\sum _{R_{R_{R}}}}$ . To accelerate the homomorphic evaluation of the PKE decryption, we introduce a method to reduce the degree of the exponentiation circuit at the cost of additional public keys. Using the same technique, we present an efficient partial solution to an open problem which is to evaluate $\mod q \bmod p$ arithmetic homomorphically for large $p$ . As an independent interest, we also obtain a generic method for converting from private-key SHE to public-key SHE. Unlike the method described by Rothblum, we are free to choose the SHE message space.

A ciphertext-policy attribute-based encryption protocol uses bilinear pairings to provide control access mechanisms, where the set of user’s attributes is specified by means of a linear secret sharing scheme. In this paper we present the design of a software cryptographic library that achieves record timings for the computation of a 126-bit security level attribute-based encryption scheme. We developed all the required auxiliary building blocks and compared the computational weight that each of them adds to the overall performance of this protocol. In particular, our single pairing and multi-pairing implementations achieve state-of-the-art time performance at the 126-bit security level.