Due to the convenience of real time monitoring and feedback, eHealth system is gaining its popularity. With the wide adoption of electronic health records (EHRs), the security issues arise at the same time. Data integrity is one of the most fundamental security requirements and many techniques have been extensively studied to provide integrity guarantee, such as digital signature. Among various signature schemes, certificateless signature enjoys the advantages of there is neither complicated certificate management nor the key escrow problem. In this paper, we study the particular security threats in eHealth systems and analyze the limitations of traditional certificateless signature schemes if being directly applied to protect data integrity. We show that there is a gap between the traditional threat model and the security threats in practice. To improve the security, we define an enhanced notion for the “normal” type adversary in certificateless signature. Then, a concrete construction secure in the enhance model is presented, which can withstand more powerful but realistic attacks. In addition, we provide experimental simulations to analyze the efficiency and security of our proposed scheme. The results demonstrate its utility in eHealth systems and other similar scenarios.

In EMR systems, numerous electronic medical records are usually uploaded to cloud servers for storage and data sharing. Public key authenticated encryption with keyword search (PAEKS) which can resist keyword guessing attacks (KGA) provides a feasible approach for data sharing and searching in EMR systems. Specifically, a PAEKS scheme requires the sender to use the receiver’s public key when encrypting, which restricts the generated ciphertext to be searchable by only one specified receiver. If a sender wants to share a data with multiple receivers, the sender has to repeatedly encrypt the data for multiple receivers using the public keys of different receivers. For the receiver, the same issue also exists in the trapdoor generation phase. Therefore, the traditional PAEKS is not suitable for EMR systems involving multiple senders and multiple receivers because of a large number of repeated computations. In this work, we present a practical scheme called multi-user keyword-field-free conjunctive searchable encryption (MU-KFFCSE). In order to achieve KGA-resistant searchable encryption between senders and receivers, we use receiver servers and sender servers such that the computation cost and communication cost of the ciphertext (trapdoor) generation phase are independent of the number of receivers (senders). The proposed scheme also supports flexible searchable encryption with keyword-field-free conjunctive utilizing polynomial technology, which not only increases the accuracy of search results, but also eliminates the limitation of fields. We prove that our scheme satisfies ciphertext indistinguishability (CI) and trapdoor indistinguishability (TI) security without random oracle. Theoretical analysis and experimental results show that our scheme is efficient in terms of computation cost and storage cost compared with existing schemes.

Cloud computing is a distributed infrastructure that centralizes server resources on a platform in order to provide services over the internet. Traditional public-key encryption protects data confidentiality in cloud computing, while functional encryption provides a more fine-grained decryption method, which only reveals a function of the encrypted data. However, functional encryption in cloud computing faces the problem of key sharing. In order to trace malicious users who share keys with others, traceable FE-IP (TFE-IP) schemes were proposed where the key generation center (KGC) knows users’ identities and binds them with different secret keys. Nevertheless, existing schemes fail to protect the privacy of users’ identities. The fundamental challenge to construct a privacy-preserving TFE-IP scheme is that KGC needs to bind a key with a user's identity without knowing the identity. To balance privacy and accountability in cloud computing, we propose the concept of privacy-preserving traceable functional encryption for inner product (PPTFE-IP) and give a concrete construction which offers the features: (1) To prevent key sharing, both a user's identity and a vector are bound together in the key; (2) The KGC and a user execute a two-party secure computing protocol to generate a key without the former knowing anything about the latter's identity; (3) Each user can ensure the integrity and correctness of his/her key through verification; (4) The inner product of the two vectors embedded in a ciphertext and in his/her key can be calculated by an authorized user; (5) Only the tracer can trace the identity embedded in a key. We formally reduce the security of the proposed PPTFE-IP to well-known complexity assumptions, and conduct an implementation to evaluate its efficiency. The novelty of our scheme is to protect the user's privacy and provide traceability if required.

Abstract A confidential reporting system (CRS) allows reporters to report concerns or problems in confidence without the fear of blame or reprisals. Nevertheless, privacy has been the primary concern of reporters. In this paper, we propose a privacy-preserving confidential reporting system with designated reporters (PPCRS-DR) to protect the privacy of reporters and the confidentiality of reports. Our PPCRS-DR provides the following interesting features: (1) for an event, an auditor can designate a reporter to report; (2) an auditor can neither see the report nor know the reporter’s identity from an encrypted report if the reporter is not the designated one; (3) when an auditor is unavailable, he/she can temporarily designate a delegatee to collect and review reports on behalf of him/her. We formalize both the definition and security model of our PPCRS-DR, and propose a concrete construction. Furthermore, the security of the proposed PPCRS-DR is formally proven. The implementation shows that it is efficient. The novelty is to implement flexible decryption delegation of CRSs and protect reporters’ privacy.

With the rise of the Internet of Things (IoT), IoT data analytics has gradually stepping into the spotlight of data mining. Existing research has primarily focused on enhancing the precision of IoT data mining, while the privacy protection aspects have not been fulfilled so far. The deployment of IoT data mining is contingent on the protection of data privacy and its economic worth to all parties. However, most existing IoT data mining research disregards economic benefits and lacks incentives, limiting its applicability. To address this issue, we provide a system for differential privacy-based IoT privacy-preserving data mining (IoT-PPDM) with dynamic incentive mechanism, and a formal economic model for IoT data mining is constructed. We utilized noncooperative game theory to simulate the multilateral interaction process in IoT data mining. To encourage participation from all parties, a dynamic incentive mechanism is designed to establish a balance between privacy protection and data mining requirements. In addition, we discuss the utility of all participants and theoretically validate the feasibility of IoT-PPDM. The experimental results show that IoT-PPDM with dynamic incentive mechanism can increase the benefits for all participants while avoiding irrational behavior of all parties.

Vehicular ad hoc networks (VANETs) serve as the foundation of intelligent transportation systems, aiming to improve communication efficiency and safety among vehicles. With the expanding applications, security and privacy have become apparent, and the large-scale message transmission imposes substantial computation and communication overheads. The technology of aggregate signature can realize message authentication and reduce both the bandwidth and computation costs significantly. In IEEE 802.11p-based VANETs, most existing aggregate signature schemes require roadside units (RSUs) to verify single signatures before calculating aggregate signatures, which is very inefficient. Furthermore, even with a valid aggregated signature, the validity of individual signatures cannot be assured. In this paper, we propose an efficient certificateless aggregate signature scheme, where RSUs do not need to validate single signatures but compute aggregate signature directly. The successful verification of the aggregated signature implies the validity of each individual signature. Additionally, to further protect data security and user privacy, this scheme employs designated verifiers for both individual and aggregate signatures. Both formal and informal security analysis are given, and performance evaluation shows our scheme exhibits lower computation and communication costs, along with more comprehensive security attributes in VANETs.

To know the most recent market conditions, an e-commerce platform needs to be aware of the sales situation of its sellers’ commodities. The most recent market conditions can help to forecast future market trends and develop policies to guide sellers in reasonably allocating their inventory proportion. Statistical analysis is a fundamental approach to studying the sales situation. However, the sales data of an e-commerce platform usually has a significant volume. Therefore, outsourcing statistical analysis to cloud servers is an effective method. Nevertheless, sellers do not want their sales data leaked to anyone or any other organization. Moreover, in many circumstances, we cannot fully trust cloud servers. Thus, we need to utilize cryptographic or non-cryptographic tools to realize the above outsourcing. Secret sharing is a lightweight and powerful non-cryptographic tool to realize privacy-preserving data analysis. However, it needs secure channels to distribute secret shares. On the other hand, homomorphic encryption is a powerful cryptographic tool for designing privacy-preserving data analysis schemes. Nevertheless, these schemes usually do not allow the entity that holds the decryption key to collude with other entities. We propose a privacy-preserving and verifiable statistical analysis scheme for an e-commerce platform that combines a threshold secret sharing scheme with a verifiable threshold homomorphic encryption scheme. Our solution’s demand for secure channels is reduced by 40% ~ 60% compared with a traditional threshold secret sharing scheme, thanking the designed novel distribution model for delivering secret shares. Furthermore, our solution has a stronger ability to resist collusive attacks, keep sales data private from any entity, and ensure that the platform can only obtain the analysis results with the help of some cloud servers, alleviating the single point of trust. And meanwhile, the novel distributed model makes our solution enjoy better robustness and fault tolerance. The proposed solution is validated through security analyses, performance evaluations, and comparison analyses.

With the rapid development of Internet of Things (IoT), big data analytics (BDA) has gradually stepped into the spotlight of IoT research. However, existing research mostly focused on improving the efficiency of data mining, the wishes and profits of the participants in BDA are largely ignored. In real systems, it is always supposed that the IoT data owners accept the big data analytics in IoT (BDA-IoT), the theoretical modeling of BDA-IoT is needed to be constructed urgently. In this paper, aiming to provide theoretical modeling of the practical application of BDA-IoT, we prove the feasibility of participants voluntarily participating in BDA-IoT for the first time. Subsequently, a non-cooperative game theory model with incentive and payment mechanisms is constructed, and the multi-parties interaction process in BDA-IoT is simulated. The overall benefits of all participants are then discussed, the rationality and feasibility of our study are proved. Simulation results show the feasibility of our model in improving the benefits of all stakeholders in a non-cooperative game, and the best choice for all participants is to accept BDA-IoT.

Patient-centered data management and sharing of personal health records (PHRs) are difficult to be realized as data is controlled by doctors/hospitals. In addition, security and privacy, oppressive costs, search and tracing unreliability, and complicated access authorization caused by traditional encryption severely hinder the widespread adoption of PHRs. To overcome these challenges, we propose a blockchain-backed data sharing framework for PHRs, where the blockchain achieves reliable search and tracing. Furthermore, we design a hybridblockchain-backedsearchableproxysigncryption scheme, namedBC-SPSC. Specifically, an identity-based proxy signature (IBPS) is utilized to perform the authorization from patients to doctors to achieve authentic patient-centricity, therefore the blockchain can relate data with associated patients and doctors during data tracing. Moreover, BC-SPSC supports two search modes. The first mode adopts attribute-based encryption with keyword-based search (SABE), where all legitimate users can implement searches, but only users whose attributes satisfy the access structure can successfully decrypt. By contrast, the second mode utilizes attribute-based searchable encryption (ABSE) to accomplish fine-grained authorization in both search and data access/decryption, that is, who can search is also constrained by data owners. Adequate performance comparisons and simulation experiments indicate significant advantages of the BC-SPSC scheme in storage and computation overheads.

With the rapid development of digital media technology, many people prefer to read e-books over article versions. The digital publishing platform can collect and analyze massive amounts of readers’ reading information. The statistical analysis results can be regarded as the platform's digital assets based on which it provides paid services for its users. However, three privacy issues are related to readers’ reading information, users’ statistical preferences, and the platform's digital assets. This article proposes a data-matching-based privacy-preserving statistic scheme. The proposed solution combines bloom filters, secret sharing, and perturbing technologies to realize an efficient match between users’ statistical preferences and massive readers’ corresponding reading information and statistical analysis of the matching results without compromising the privacy of different parties. Besides, the proposed solution adopts an edge computing paradigm to realize the process of massive data in a divide-and-conquer parallel way. It introduces the concepts of Mirror Secret Shares and Buddy Edge Devices to virtualize the$(m+1, m+1)$-threshold secret sharing scheme to an$(m+1, m+\lfloor m/2 \rfloor +2)$-threshold secret sharing scheme for achieving good robustness without adding hardware devices. The detailed analyses show that our solution meets the defined design goals. Furthermore, the experimental results demonstrate the efficiency of the proposed work.

In a traditional health system, it merely depends on doctors’ initiative reports to discover infectious diseases, which causes late responses from the Center for Disease Control (CDC) and therefore may result in snowballed loss of lives and economy. Sometimes, the disease has spread when doctors realize it is infectious, and the CDC has to invest more human and material resources to control it. In this article, we propose a new secure infectious diseases detection system with the help of the IoT-based e-health platform. In our system model, the hospitals collect patients’ electronic health records (EHRs) and outsource the encrypted EHRs to the contracted cloud. The CDC can regularly send a test query to the cloud server to check whether there are patients who have similar symptoms or some increasing signs, which are regarded as signs of infectious diseases. With this system, the CDC can find the small signs of infectious diseases so that it can make appropriate and timely measures to save more lives. To enable the cloud server to perform the required test, we propose a new cryptographic notion, called public-key encryption with DFET (PKE-DFET), with which we can check whether the underlying messages of two ciphertexts are equal or not after ignoring the bits on designated positions without decryption. The cloud server can utilize the PKE-DFET to flexibly count the number of patients with similar symptoms following the CDC’s instructions. We first instantiate the PKE-DFET into a concrete construction, where anyone can be a tester to perform the DFET on ciphertexts. Finally, we extend our PKE-DFET construction to enable it to be flexible in different actual application scenarios.

Cloud computing enables users to remove the necessity of the need of local hardware architecture, which removes the burden of the users from high computation costs. Therefore, it has attracted much attention and research has been conducted heavily on it. To protect users’ privacy, data is usually encrypted prior to being sent to the cloud server. As the resulting system is unusable, since the cloud can no longer search throughout the data, new cryptographic primitive such as public-key encryption with equality test (PKEET) has been introduced. In PKEET, users can test whether the underlying messages of two ciphertexts encrypted under different public keys are equal or not without the need to decrypt those ciphertexts. This is a very useful tool, especially for the cloud database, since PKEET mainly focuses on the equality test between two ciphertexts. However, in practice, the cloud server may need to verify the equivalence among more than two ciphertexts. This leads to disclosing unnecessary information of users and redundant computation cost will also occur when using traditional PKEET schemes. How to make this more efficient and practical remains an interesting research problem. In this article, to solve the aforementioned problems by providing a novel concept of public-key encryption with multi-ciphertext equality test (PKE-MET). In PKE-MET, each ciphertext can designate a number$s$such that the cloud server can only perform equality test on this ciphertext with other$s-1$ciphertexts, where all their designated numbers are$s$. For PKE-MET, besides traditional OW-CPA and IND-CPA security, we specially define Number security. We instantiate PKE-MET to a concrete scheme and give its security proof. Furthermore, to enable the primitive to be more practical in applications, we extend it to the concept of PKE with flexible MET (PKE-FMET). In PKE-FMET, the cloud server can perform equality test on any number of ciphertexts as long as the maximum number of their designated numbers is less than or equal to the number of ciphertexts. We construct a PKE-FMET scheme based on our PKE-MET construction and prove its security under the defined security models. Besides, the performance analysis mainly of efficiency and security between our constructions and existing equality test schemes in cloud computing show that our proposed schemes are more efficient and secure in the multi-ciphertext scenario.

Cloud computing offers on-demand availability of computing resources over the Internet. To attract users, cloud providers offer their resources as services at reasonable prices and provide various price models to reflect higher level of quality of service (QoS), which are referred as pricing schemes.$k$-times anonymous authentication ($k$-TAA) is an attractive approach to construct pricing schemes, providing access controllability, user anonymity and public traceability. In$k$-TAA schemes, authenticated users are permitted to anonymously access services from a provider at most$k$times, while the ones whose the number of access times exceeds$k$can be publicly traced. That is,$k$-TAA schemes offer a prepaid plan that charges users based on the amount of access times. Alternatively, pay-as-you-go (PAYG) is a pricing strategy that allows users to be charged based on the amount of usage, reducing the costs on unnecessary resources. Adopting$k$-TAA schemes to PAYG model, the access bound$k$is decided by the prepayment amount and the service usage is tracked by the number of access times. However, this approach is impractical, since existing$k$-TAA schemes only allow an one-time access in an authentication. This article aims to bridge this gap in the literature by designing an efficient and secure authentication system for PAYG cloud computing, supporting flexible access controllability, user anonymity and public traceability. To achieve this, we propose a new$k$-TAA primitive, called$k$-times anonymous pay-as-you-go authentication ($k$-TAA-PAYG), that allows users to access services for multiple times in an authentication as long as the number of their access times does not exceed$k$. We first formalize the definition and security model for$k$-TAA-PAYG scheme. Subsequently, we present a concrete construction of$k$-TAA-PAYG scheme, with the computational complexity as$O(1)$and the constant communicational cost. Finally, comparing with the most efficient$k$-TAA scheme proposed by Emuraet al., the experimental results show that our$k$-TAA-PAYG scheme is 2.5 to 3 times faster and saves up to 66 percent storage in grant processes. The time cost of an authentication of our$k$-TAA-PAYG scheme is constant (1.4-2.4 ms), while Emuraet al.’s scheme needs more than one second when the number of access time is greater than 1, 000.

Abstract A tightly secure scheme has a reduction, where the reduction loss is a small constant. Identity-based signature (IBS) is an important cryptographic primitive, and tightly secure IBS schemes enjoy the advantage that the security parameter can be optimal to achieve a certain security level. General constructions of IBS schemes (Bellare, M., Namprempre, C., and Neven, G. (2004) Security Proofs for Identity-Based Identification and Signature Schemes. In Proc. EUROCRYPT 2004, May 2–6, pp. 268–286. Springer, Berlin, Interlaken, Switzerland; Galindo, D., Herranz, J., and Kiltz, E. (2006) On the Generic Construction of Identity-Based Signatures With Additional Properties. In Proceedings of ASIACRYPT 2006, December 3–7, pp. 178–193. Springer, Berlin, Shanghai, China) and their security have been extensively studied. However, the security is not tight and how to generally construct a tightly secure IBS scheme remains unknown. In this paper, we concentrate on the general constructions of IBS schemes. We first take an insight into previous constructions and analyze the reason why it cannot achieve tight security. To further study possible tightly secure constructions, we propose another general construction, which could be seen as a different framework of IBS schemes. Our construction requires two traditional signature schemes, whereas the construction by Bellare et al. uses one scheme in a two-round iteration. There are no additional operations in our general construction. Its main advantage is providing the possibility of achieving tight security for IBS schemes in the random oracle model. Combining two known signature schemes, we present an efficient IBS scheme with tight security as an example.

Abstract Identity-based revocation system (IBRS) generates the ciphertext with a revoked identity list such that only the non-revoked identities can use their private keys to decrypt this ciphertext. IBRS can be efficiently applied in some practical applications, such as the pay-TV systems when the number of revoked identities are much less than the non-revoked ones. However, since IBRS is based on identity-based cryptography, it also suffers from the inherent key escrow problem where the private key generator (PKG) has full control of each user’s private key. As a consequence, it is hard to judge whether a pirated private key is generated by the PKG or the suspected user. There is no study on IBRS fulfilling accountability in literature to date. In this paper, we introduce the notion of accountable authority IBRS (A-IBRS), which provides accountability in IBRS schemes. In an A-IBRS, the aforementioned problem can be alleviated and resolved. Furthermore, a full black-box A-IBRS can distinguish the creator of a black box between the PKG and the associated user and the dishonest PKG is allowed to access the decryption results of the user private key. We formalize the definition and security models of the full black-box A-IBRS schemes. Then, we present a concrete full black-box A-IBRS scheme with constant-size master public key and private key. Finally, we prove the security of our scheme under the defined security models without random oracle.

The networks of intelligent building are usually consist of a great number of smart devices. Since many smart devices only support on-site configuration and upgrade, and communication between devices could be observed and even altered by attackers, efficiency and security are two key concerns in maintaining and managing the devices used in intelligent building networks. In this paper, the authors apply the technology of software defined networking to satisfy the requirement for efficiency in intelligent building networks. More specific, a protocol stack in smart devices that support OpenFlow is designed. In addition, the authors designed the lightweight security mechanism with two foundation protocols and a full protocol that uses the foundation protocols as example. Performance and session key establishment for the security mechanism are also discussed.