Yupeng Zhang, Jonathan Katz, Charalampos Papamanthou
We present a new construction of an expressive set accumulator. Unlike existing cryptographic accumulators, ours provides succinct proofs for a large collection of operations over accumulated sets, including intersection, union, set difference, SUM, COUNT, MIN, MAX, and RANGE, as well as arbitrary nestings of the above. We also show how to extend our accumulator to be zero-knowledge. The security of our accumulator is based on extractability assumptions and other assumptions that hold in the generic group model. Our construction has asymptotically optimal verification complexity and proof size, constant update complexity, and public verifiability/updatability-namely, any client who knows the public key and the last accumulator value can verify the supported operations and update the accumulator. The expressiveness of our accumulator comes at the cost of quadratic prover time. However, we show that the cryptographic operations involved are cheap compared to those incurred by generic approaches (e.g., SNARKs) that are equally expressive: our prover runs faster for sets of up to 5 million items. Our accumulator serves as a powerful cryptographic tool with many applications. For example, it can be applied to efficiently support verification of a rich collection of SQL queries when used as a drop-in replacement in existing verifiable database systems (e.g., IntegriDB, CCS 2015).
Trusted hardware systems, such as Intel's new SGX instruction set architecture extension, aim to provide strong confidentiality and integrity assurances for applications. Recent work, however, raises serious concerns about the vulnerability of such systems to side-channel attacks. We propose, formalize, and explore a cryptographic primitive called a Sealed-Glass Proof (SGP) that models computation possible in an isolated execution environment with unbounded leakage, and thus in the face of arbitrary side-channels. A SGP specifically models the capabilities of trusted hardware that can attest to correct execution of a piece of code, but whose execution is transparent, meaning that an application's secrets and state are visible to other processes on the same host. Despite this strong threat model, we show that SGPs enable a range of practical applications. Our key observation is that SGPs permit safe verifiable computing in zero-knowledge, as data leakage results only in the prover learning her own secrets. Among other applications, we describe the implementation of an end-to-end bug bounty (or zero-day solicitation) platform that couples a SGX-based SGP with a smart contract. Our platform enables a marketplace that achieves fair exchange, protects against unfair bounty withdrawals, and resists denial-of-service attacks by dishonest sellers. We also consider a slight relaxation of the SGP model that permits black-box modules instantiating minimal, side-channel resistant primitives, yielding a still broader range of applications. Our work shows how trusted hardware systems such as SGX can support trustworthy applications even in the presence of side channels.
Security and Verification in Computing
Cloud Data Security Solutions
Physical Unclonable Functions (PUFs) and Hardware Security
Igor Zikratov, Alexander Kuzmin, Vladislav Akimenko, Viktor Niculichev · 5 authors
Blockchain is a relatively new technology that has shown a lot of possibilities. It emerged in 2009 as a public ledger of all Bitcoin transactions. Blockchain technology is finding applications in wide range of areas: digital assets and stocks, smart contracts, record keeping, ID systems, cloud storage, ride sharing, etc. We investigate the blockchains' activity in terms of how to store, retrieve and share files in decentralized network.
We present the concept of leveraging Blockchain technology, for the management and security of information related to the Internet Of Things. Here, we put forth a model for the intercommunication of smart devices, their identity management and information security, with Blockchain posing as the backbone. The model proposes to serve as a robust and scalable solution, in order to address the security and identity concerns, arising due to the distributed nature of the Internet of Things. The proposed model is further compared to the existing ones in practice.
In recent years, volunteer service in China has made an unprecedented development, but the credibility and traceability of volunteer service time management are confronted with serious challenges. Since traditional time record systems cannot protect the related data security of the volunteers. In this paper, we study the volunteer time record system based on the blockchain technology which is the core technology of bitcoin, unlike bitcoin transaction in our system are not strictly financial - they are used to carry instructions, such as storing, querying, and sharing data. Volunteer service time and activity information recorded by sending the chain transaction. Effective time recognition is guaranteed by smart contract. It can ensure that the volunteer's time is independent of improper human interference, and the fairness of volunteer service, realizes the traceability and transparency of the entire time record process. Then we describe a specific case and use the system we proposed storing the volunteer service time, volunteers' service time can be certified effectively.
We propose a new secure online storage scheme based on an open P2P network without a central server. In the proposed scheme, attackers cannot detect target user data in the online storage because the user data is divided into some parts by the secret sharing, and they are distributed to P2P nodes via the anonymous communication. The proposed scheme can prevent the direct attack on the target user node because metadata for the reconstruction also hidden in the online storage, hence nothing remains in the user node. Even if the state of the P2P network varies over time between the storing and restoring operation, the proposed scheme ensures that the user can identify the target nodes which stored his metadata by utilizing the Blockchain technology with only memorable secure information for user authentication. Furthermore, a malicious node to attack on others can be detected and ruled out by the mutual monitoring among the nodes and the majority decision rule.
M. Suguna, R. Anusia, S. Mercy Shalinie, S. Renu Deepti
Mobile cloud computing (MCC) is a platform that allows mobile users to offload the computationally rigorous and storage demanding tasks on available cloud resources using wireless access. The major concern with MCC is the privacy of data. Mobile users give confidential information through the network, that if not safeguarded may lead to security issues. Identity Management (IDM) is the management of user identities, their authentication, and authorization in the cloud environment. The existing Consolidated Identity Management (CIDM) overcomes the network traffic interception in the traditional IDM but is prone to Identity theft in case of Identity Management Server (IDMS) compromise. This work is focused on the development of a Secure Identity Management (SIDM) that alleviates the attacks in the CIDM by using techniques that strengthens the authentication process and identity privacy. A secure IDM is developed using two-step authentication process which involves Zero Knowledge Proof (ZKP) and token verification. The proposed SIDM model reduces the consequences of Identity server compromise attack. There is a marginal increase in the communication overhead of SIDM compared to that of CIDM but it can be compromised to realize the benefits of identity privacy. The analysis of the experimental results shows that there is an overall increase of thirty percent in communication overhead when compared to CIDM.
Data is nowadays an invaluable resource, indeed it guides all business decisions in most of the computer-aided human activities. Threats to data integrity are thus of paramount relevance, as tampering with data may maliciously affect crucial business decisions. This issue is especially true in cloud computing environments, where data owners cannot control fundamental data aspects, like the physical storage of data and the control of its accesses. Blockchain has recently emerged as a fascinating technology<br> which, among others, provides compelling properties about data integrity. Using the blockchain to face data integrity threats seems to be a natural choice, but its current limitations of low throughput, high latency, and weak stability hinder the practical feasibility of any blockchain-based solutions.<br> In this paper, by focusing on a case study from the European SUNFISH project, which concerns the design of a secure by-design cloud federation platform for the public sector, we precisely delineate the actual data integrity needs of cloud computing environments and the research questions to be tackled to adopt blockchain-based databases. First, we detail the open research questions and the difficulties inherent in addressing them. Then, we outline a preliminary design of an effective blockchain-based database for cloud computing environments.
This thesis presents an extension to Hyperledger Fabric, a private blockchain system, allowing historic transactions to be pruned without peer coordination. The feature is facilitated via pruning predicate functions, provided along any smart contracts a given system is desired to host. An evaluation of the extension demonstrates its impact, in terms of memory saved, for a specific asset delivery use case. It is concluded that the gains of pruning historic transactions from blockchain systems could yield significantly reduced storage requirements for some categories of applications, especially such with low transaction interdependency. It is also suggested that the deterministic consensus algorithms used by Hyperledger Fabric makes the transaction histories it may maintain not strictly required, meaning that the particular set of transactions that must survive pruning depend on what properties a blockchain is expected to maintain.
With the rise of Bitcoin, blockchain which is the core technology of Bitcoin has received increasing attention. Privacy preserving and performance on blockchain are two research points in academia and business, but there are still some unresolved issues in both respects. An aggregate signature scheme is a digital signature that supports making signatures on many different messages generated by many different users. Using aggregate signature, the size of the signature could be shortened by compressing multiple signatures into a single signature. In this paper, a new signature scheme for transactions on blockchain based on the aggregate signature was proposed. It was worth noting that elliptic curve discrete logarithm problem and bilinear maps played major roles in our signature scheme. And the security properties of our signature scheme were proved. In our signature scheme, the amount will be hidden especially in the transactions which contain multiple inputs and outputs. Additionally, the size of the signature on transaction is constant regardless of the number of inputs and outputs that the transaction contains, which can improve the performance of signature. Finally, we gave an application scenario for our signature scheme which aims to achieve the transactions of big data on blockchain.
With the rise of Bitcoin, cryptographic currencies have attracted more and more attention. Subsequently, other cryptographic currencies were gradually created, such as Zcash, Moreno, Dash and so on. In cryptographic currency, privacy preserving and expansion are two key technical points. In terms of privacy preserving, more effective solutions were proposed in Zcach, Moreno, Dash and other cryptographic currencies systems, in which ring signature, zero knowledge proof and other cryptographic techniques played important roles. But these schemes mainly considered protecting the addresses of both sides of the transaction. In terms of expansion, lightning network and other projects also give solutions. But most of these projects will bring other problems. In this paper, a signature scheme based on the aggregate signature and the elliptic curve algorithm is proposed to hide the transaction value of a single sender and receiver in the transactions which contain multiple inputs and outputs. This signature scheme achieves the purpose of privacy preserving from the transaction value. Further, the correctness proof and security analysis are given in this paper. In addition to that, another signature scheme that combines aggregation signature with bilinear ring signature is proposed. This aggregate ring signature scheme gives another attempt to solve the problem of expansion in the cryptographic currency system only using cryptographic technologies. At the same time, the sender's addresses can be hidden. Similarly, we also confirmed the correctness of this signature scheme.
In the last decades, we have witnessed an exploding growth of the Internet. The massive adoption of distributed systems on the Internet allows users to offload their computing intensive work to remote servers, e.g. cloud. In this context, distributed systems are pervasively used in a number of difference scenarios, such as web-based services that receive and process data, cloud nodes where company data and processes are executed, and softwarised networks that process packets. In these systems, all the computing entities need to trust each other and co-operate in order to work properly. While the communication channels can be well protected by protocols like TLS or IPsec, the problem lies in the expected behaviour of the remote computing platforms, because they are not under the direct control of end users and do not offer any guarantee that they will behave as agreed. For example, the remote party may use non-legitimate services for its own convenience (e.g. illegally storing received data and routed packets), or the remote system may misbehave due to an attack (e.g. changing deployed services). This is especially important because most of these computing entities need to expose interfaces towards the Internet, which makes them easier to be attacked. Hence, software-based security solutions alone are insufficient to deal with the current scenario of distributed systems. They must be coupled with stronger means such as hardware-assisted protection. In order to allow the nodes in distributed system to trust each other, their integrity must be presented and assessed to predict their behaviour. The remote attestation technique of trusted computing was proposed to specifically deal with the integrity issue of remote entities, e.g. whether the platform is compromised with bootkit attacks or cracked kernel and services. This technique relies on a hardware chip called Trusted Platform Module (TPM), which is available in most business class laptops, desktops and servers. The TPM plays as the hardware root of trust, which provides a special set of capabilities that allows a physical platform to present its integrity state. With a TPM equipped in the motherboard, the remote attestation is the procedure that a physical node provides hardware-based proof of the software components loaded in this platform, which can be evaluated by other entities to conclude its integrity state. Thanks to the hardware TPM, the remote attestation procedure is resistant to software attacks. However, even though the availability of this chip is high, its actual usage is low. The major reason is that trusted computing has very little flexibility, since its goal is to provide strong integrity guarantees. For instance, remote attestation result is positive if and only if the software components loaded in the platform are expected and loaded in a specific order, which limits its applicability in real-world scenarios. For such reasons, this technique is especially hard to be applied on software services running in application layer, that are loaded in random order and constantly updated. Because of this, current remote attestation techniques provide incomplete solution. They only focus on the boot phase of physical platforms but not on the services, not to mention the services running in virtual instances. This work first proposes a new remote attestation framework with the capability of presenting and evaluating the integrity state not only of the boot phase of physical platforms but also of software services at load time, e.g. whether the software is legitimate or not. The framework allows users to know and understand the integrity state of the whole life cycle of the services they are interacting with, thus the users can make informed decision whether to send their data or trust the received results. Second, based on the remote attestation framework this thesis proposes a method to bind the identity of secure channel endpoint to a specific physical platform and its integrity state. Secure channels are extensively adopted in distributed systems to protect data transmitted from one platform to another. However, they do not convey any information about the integrity state of the platform or the service that generates and receives this data, which leaves ample space for various attacks. With the binding of the secure channel endpoint and the hardware TPM, users are protected from relay attacks (with hardware-based identity) and malicious or cracked platform and software (with remote attestation). Third, with the help of the remote attestation framework, this thesis introduces a new method to include the integrity state of software services running in virtual containers in the evidence generated by the hardware TPM. This solution is especially important for softwarised network environments. Softwarised network was proposed to provide dynamic and flexible network deployment which is an ever complex task nowadays. Its main idea is to switch hardware appliances to softwarised network functions running inside virtual instances, that are full-fledged computational systems and accessible from the Internet, thus their integrity is at stake. Unfortunately, currently remote attestation work is not able to provide hardware-based integrity evidence for software services running inside virtual instances, because the direct link between the internal of virtual instances and hardware root of trust is missing. With the solution proposed in this thesis, the integrity state of the softwarised network functions running in virtual containers can be presented and evaluated with hardware-based evidence, implying the integrity of the whole softwarised network. The proposed remote attestation framework, trusted channel and trusted softwarised network are implemented in separate working prototypes. Their performance was evaluated and proved to be excellent, allowing them to be applied in real-world scenarios. Moreover, the implementation also exposes various APIs to simplify future integration with different management platforms, such as OpenStack and OpenMANO.
Generally scarce computational and memory resource availability is a well known problem for the IoT, whose intrinsic volatility makes complex applications unfeasible. Noteworthy efforts in overcoming unpredictability (particularly in case of large dimensions) are the ones integrating Knowledge Representation technologies to build the so-called Semantic Web of Things (SWoT). In spite of allowed advanced discovery features, transactions in the SWoT still suffer from not viable trust management strategies. Given its intrinsic characteristics, blockchain technology appears as interesting from this perspective: a semantic resource/service discovery layer built upon a basic blockchain infrastructure gains a consensus validation. This paper proposes a novel Service-Oriented Architecture (SOA) based on a semantic blockchain for registration, discovery, selection and payment. Such operations are implemented as smart contracts, allowing distributed execution and trust. Reported experiments early assess the sustainability of the proposal.