Biblio

The COVID-19 pandemic has recently emerged as a worldwide health emergency that necessitates coordinated international measures. To contain the virus's spread, governments and health organisations raced to develop vaccines that would lower Covid-19 morbidity, relieve pressure on healthcare systems, and allow economies to open. Following the COVID-19 vaccine, the vaccination certificate has been adopted to help the authorities formulate policies by controlling cross-border travelling. To address serious privacy concerns and eliminate the need for third parties to retain the trust and govern user data, in this paper, we leverage blockchain technologies in developing a secure and verifiable vaccination certificate. Our approach has the advantage of utilising a hybrid approach that implements different advanced technologies, such as the self-sovereignty concept, smart contracts and interPlanetary File System (IPFS). We rely on verifiable credentials paired with smart contracts to make decisions about who can access the system and provide on-chain verification and validation of the user and issuer DIDs. The approach was further analysed, with a focus on performance and security. Our analysis shows that our solution satisfies the security requirements for immunisation certificates.

Blockchain-based cryptocurrencies offer an appealing alternative to Fiat currencies, due to their decentralized and borderless nature. However the decentralized settings make the authentication process more challenging: Standard cryptographic methods often rely on the ability of users to reliably store a (large) secret information. What happens if one user's key is lost or stolen? Blockchain systems lack of fallback mechanisms that allow one to recover from such an event, whereas the traditional banking system has developed and deploys quite effective solutions. In this work, we develop new cryptographic techniques to integrate security policies (developed in the traditional banking domain) in the blockchain settings. We propose a system where a smart contract is given the custody of the user's funds and has the ability to invoke a two-factor authentication (2FA) procedure in case of an exceptional event (e.g., a particularly large transaction or a key recovery request). To enable this, the owner of the account secret-shares the answers of some security questions among a committee of users. When the 2FA mechanism is triggered, the committee members can provide the smart contract with enough information to check whether an attempt was successful, and nothing more. We then design a protocol that securely and efficiently implements such a functionality: The protocol is round-optimal, is robust to the corruption of a subset of committee members, supports low-entropy secrets, and is concretely efficient. As a stepping stone towards the design of this protocol, we introduce a new threshold homomorphic encryption scheme for linear predicates from bilinear maps, which might be of independent interest. To substantiate the practicality of our approach, we implement the above protocol as a smart contract in Ethereum and show that it can be used today as an additional safeguard for suspicious transactions, at minimal added cost. We also implement a second scheme where the smart contract additionally requests a signature from a physical hardware token, whose verification key is registered upfront by the owner of the funds. We show how to integrate the widely used universal two-factor authentication (U2F) tokens in blockchain environments, thus enabling the deployment of our system with available hardware.

Due to the computing capability limitation of the Internet of things devices in the perception layer, the traditional security solutions are difficult to be used directly. How to design a new lightweight, secure and reliable protocol suitable for the Internet of Things application environment, and realize the secure transmission of information among many sensing checkpoints is an urgent problem to be solved. In this paper, we propose a decentralized lightweight authentication key protocol based on the combination of public key and trusted computing technology, which is used to establish secure communication between nodes in the perception layer. The various attacks that the protocol may suffer are analyzed, and the formal analysis method is used to verify the security of the protocol. To verify the validity of the protocol, the computation and communication cost of the protocol are compared with the existing key protocols. And the results show that the protocol achieved the promised performance.

Tor is a famous routing overlay network based on the Onion multi-layered encryption to support communication anonymity in a threat model in which some network nodes are malicious. However, Tor does not provide any protection against the global passive adversary. In this threat model, an idea to obtain recipient anonymity, which is enough to have relationship anonymity, is to hide the recipient among a sufficiently large anonymity set. However, this would lead to high latency both in the set-up phase (which has a quadratic cost in the number of involved nodes) and in the successive communication. In this paper, we propose a way to arrange a Tor circuit with a tree-like topology, in which the anonymity set consists of all its nodes, whereas set-up and communication latency depends on the number of the sole branch nodes (which is a small fraction of all the nodes). Basically, the cost goes down from quadratic to linear. Anonymity is obtained by applying a broadcast-based technique for the forward message, and cover traffic (generated by the terminal-chain nodes) plus mixing over branch nodes, for the response.

k-anonymity is a well-known definition of privacy, which guarantees that any person in the released dataset cannot be distinguished from at least k-1 other individuals. In the protection model, the records are anonymized through generalization or suppression with a fixed value of k. Accordingly, each record has the same level of anonymity in the published dataset. However, different people or items usually have inconsistent privacy requirements. Some records need extra protection while others require a relatively low level of privacy constraint. In this paper, we propose Multi-Level Privacy Preserving K-Anonymity, an advanced protection model based on k-anonymity, which divides records into different groups and requires each group to satisfy its respective privacy requirement. Moreover, we present a practical algorithm using clustering techniques to ensure the property. The evaluation on a real-world dataset confirms that the proposed method has the advantages of offering more flexibility in setting privacy parameters and providing higher data utility than traditional k-anonymity.

Malicious software (malware) creators are constantly mutating malware files in order to avoid detection, resulting in hundreds of millions of new malware every year. Therefore, most malware files are unlabeled due to the time and cost needed to label them manually. This makes it very challenging to perform malware detection, i.e., deciding whether a file is malware or not, and malware classification, i.e., determining the family of the malware. Most solutions use supervised learning (e.g., ResNet and VGG) whose accuracy degrades significantly with the lack of abundance of labeled data. To solve this problem, this paper proposes a semi-supervised learning model for image-based malware classification. In this model, malware files are represented as grayscale images, and semi-supervised learning is carefully selected to handle the plethora of unlabeled data. Our proposed model is an enhanced version of the ∏-model, which makes it more accurate and consistent. Experiments show that our proposed model outperforms the original ∏-model by 4% in accuracy and three other supervised models by 6% in accuracy especially when the ratio of labeled samples is as low as 20%.

Return-oriented programming(ROP) is a prevalent technique that targets return addresses to hijack control flow. To prevent such attack, researchers mainly focus on either Shadow Stack or MAC-based mechanisms(message code authentication). But Shadow Stack suffers from additional memory overhead and information leakage, while MAC-based mechanisms(e.g. Zipper Stack) impose high runtime overhead for MAC calculations.In this paper, we propose Twine Stack, a hybrid and efficient return address protection mechanism with lightweight hardware extension. It utilizes a tiny hardware shadow stack to realize a new multi-chain Zipper Stack. Specifically, each entry in the shadow stack stores a return address and its MAC in each chain, allowing queueing calculation with just one hash module. At meantime, some return address verifications could be done by comparison with the hardware shadow stack, instead of calculation again. We implemented Twine Stack on RISC-V architecture, and evaluated it on FPGA board. Our experiments show that Twine Stack reduces over 95% hash verifications, and imposes merely 1.38% performance overhead with an area overhead of 974 LUTs and 726 flip flops. The result demonstrates that our hybrid scheme mitigates the drawbacks of each separate scheme.

Signcryption is a sophisticated cryptographic tool that combines the benefits of digital signature and data encryption in a single step, resulting in reduced computation and storage cost. However, the existing signcryption techniques do not account for a scenario in which a company must escrow an employee's private encryption key so that the corporation does not lose the capacity to decrypt a ciphertext when the employee or user is no longer available. To circumvent the issue of non-repudiation, the private signing key does not need to be escrowed. As a result, this paper presents an implicit certificate-based signcryption technique with private encryption key escrow, which can assist an organization in preventing the loss of private encryption. A certificate, or more broadly, a digital signature, protects users' public encryption and signature keys from man-in-the-middle attacks under our proposed approach.

Edge data caching has attracted tremendous attention in recent years. Service providers can consider caching data on nearby locations to provide service for their app users with relatively low latency. The key to enhance the user experience is appropriately choose to cache data on the suitable edge servers to achieve the service providers' objective, e.g., minimizing data retrieval latency and minimizing data caching cost, etc. However, Quality of Experience (QoE), which impacts service providers' caching benefit significantly, has not been adequately considered in existing studies of edge data caching. This is not a trivial issue because QoE and Quality-of-Service (QoS) are not correlated linearly. It significantly complicates the formulation of cost-effective edge data caching strategies under the caching budget, limiting the number of cache spaces to hire on edge servers. We consider this problem of QoE-aware edge data caching in this paper, intending to optimize users' overall QoE under the caching budget. We first build the optimization model and prove the NP-completeness about this problem. We propose a heuristic approach and prove its approximation ratio theoretically to solve the problem of large-scale scenarios efficiently. We have done extensive experiments to demonstrate that the MPSG algorithm we propose outperforms state-of-the-art approaches by at least 68.77%.

The popularity of P2P (Peer-To-Peer) systems is increased tremendously due to massive increase in the Internet based applications. Initially, P2P systems were mainly designed for wired networks but today people are using more wireless networks and therefore these systems are gaining popularity. There are many wireless networks available today and WMNs (Wireless Mess Networks) are gaining popularity due to hybrid structure. People are using structured P2P systems-based applications within perimeter of a WMN. Structured P2P WMNs will assist the community to fetch the relevant information to accomplish their activities. There are inherent challenges in the structured P2P network and increased in wireless environment like WMNs. Structured P2P systems suffer from many challenges like lack of content availability, malicious content distribution, poor search scalability, free riding behaviour, white washing, lack of a robust trust model etc. Whereas, WMNs have limitations like mobility management, bandwidth constraint, limited battery power of user's devices, security, maintenance etc. in remote/ forward areas. We exploit the better possibility of content availability and search scalability in this paper. We propose replication schemes based on the popularity of content for structured P2P system applications in community based WMNs. The analysis of the performance shows that proposed scheme performs better than the existing replication scheme in different conditions.

The traditional data storage method often adopts centralized architecture, which is prone to trust and security problems. This paper proposes a trusted data storage and access control scheme combining blockchain and attribute-based encryption, which allow cyber-physical system (CPS) nodes to realize the fine-grained access control strategy. At the same time, this paper combines the blockchain technology with distributed storage, and only store the access control policy and the data access address on the blockchain, which solves the storage bottleneck of blockchain system. Furthermore, this paper proposes a novel multi-authority attributed-based identification method, which realizes distributed attribute key generation and simplifies the pairwise authentication process of multi-authority. It can not only address the key escrow problem of one single authority, but also reduce the problem of high communication overhead and heavy burden of multi-authority. The analyzed results show that the proposed scheme has better comprehensive performance in trusted data storage and access control for power cyber-physical system.

To break the data barrier of the information island and explore the value of data in the past few years, it has become a trend of uploading data to the cloud by data owners for data sharing. At the same time, they also hope that the uploaded data can still be controlled, which makes access control of cloud data become an intractable problem. As a famous cryptographic technology, ciphertext policy-based attribute encryption (CP-ABE) not only assures data confidentiality but implements fine-grained access control. However, the actual application of CP-ABE has its inherent challenge in attribute revocation. To address this challenge, we proposed an access control solution supporting attribute revocation in cloud computing. Unlike previous attribute revocation schemes, to solve the problem of excessive attribute revocation overhead, we use symmetric encryption technology to encrypt the plaintext data firstly, and then, encrypting the symmetric key by utilizing public-key encryption technology according to the access structure, so that only the key ciphertext is necessary to update when the attributes are revoked, which reduces the spending of ciphertext update to a great degree. The comparative analysis demonstrates that our solution is reasonably efficient and more secure to support attribute revocation and access control after data sharing.

Driven by the development of Internet and information technology, cloud computing has been widely recognized and accepted by the public. However, with the occurrence of more and more information leakage, cloud security has also become one of the core problem of cloud computing. As one of the resolve methods of it, ciphertext-policy attribute-based encryption (CP-ABE) by embedding access policy into ciphertext can make data owner to decide which attributes can access ciphertext. It achieves ensuring data confidentiality with realizing fine-grained access control. However, the traditional access policy has some limitations. Compared with other access policies, the circuit-based access policy ABE supports more flexible access control to encrypted data. But there are still many challenges in the existing circuit-based access policy ABE, such as privacy leakage and low efficiency. Motivated by the above, a new circuit-based access policy ABE is proposed. By converting the multi output OR gates in monotonic circuit, the backtracking attacks in circuit access structure is avoided. In order to overcome the low efficiency issued by circuit conversion, outsourcing computing is adopted to Encryption/Decryption algorithms, which makes the computing overhead for data owners and users be decreased and achieve constant level. Security analysis shows that the scheme is secure under the decision bilinear Diffie-Hellman (DBDH) assumption. Numerical results show the proposed scheme has a higher computation efficiency than the other circuit-based schemes.

The Internet of Things integrates multiple hardware appliances from large cloud data centres to constrained devices embedded within the physical reality, from multiple vendors and providers, under the same infrastructure. These appliances are subject to different restrictions, have different available resources and show different risk profiles and vulnerabilities. In these scenarios, remote attestation mechanisms are essential, enabling the verification of a distant appliance’s internal state before allowing it to access sensitive data or execute critical workloads. This work proposes a new attestation approach based on a Trusted Platform Module (TPM), devoted to performing Remote Attestation as a Service (RAaaS) while guaranteeing essential properties such as flexibility, generality, domain separation and authorized initiation. The proposed solution can prove both edge devices and IoT devices reliability to services running on cloud data centres. Furthermore, the first prototype of this service has been validated and evaluated via a real use case.

Cross-site scripting (XSS) is a common security vulnerability found in web applications. DOM-based XSS, one of the variants, is becoming particularly more prevalent with the boom of single-page applications where most of the UI changes are achieved by modifying the DOM through in-browser scripting. It is very easy for developers to introduce XSS vulnerabilities into web applications since there are many ways for user-controlled, unsanitized input to flow into a Web API and get interpreted as HTML markup and JavaScript code. An emerging Web API proposal called Trusted Types aims to prevent DOM XSS by making Web APIs secure by default. Different from other XSS mitigations that mostly focus on post-development protection, Trusted Types direct developers to write XSS-free code in the first place. A common concern when adopting a new security mechanism is how much effort is required to refactor existing code bases. In this paper, we report a case study on adopting Trusted Types in a well-established web framework. Our experience can help the web community better understand the benefits of making web applications compatible with Trusted Types, while also getting to know the related challenges and resolutions. We focused our work on Angular, which is one of the most popular web development frameworks available on the market.