Ali Nikhalat Jahromi, Ali Mohammad Saghiri, Mohammad Reza Meybodi
The Bitcoin cryptocurrency has received much attention recently. In the network of Bitcoin, transactions are recorded in a ledger. In this network, the process of recording transactions depends on some nodes called miners that execute a protocol known as mining protocol. One of the significant aspects of mining protocol is incentive compatibility. However, literature has shown that Bitcoin mining's protocol is not incentive-compatible. Some nodes with high computational power can obtain more revenue than their fair share by adopting a type of attack called the selfish mining attack. In this paper, we propose an artificial intelligence-based defense against selfish mining attacks by applying the theory of learning automata. The proposed defense mechanism ignores private blocks by assigning weight based on block discovery time and changes current Bitcoin's fork resolving policy by evaluating branches' height difference in a self-adaptive manner utilizing learning automata. To the best of our knowledge, the proposed protocol is the literature's first learning-based defense mechanism. Simulation results have shown the superiority of the proposed mechanism against tie-breaking mechanism, which is a well-known defense. The simulation results have shown that the suggested defense mechanism increases the profit threshold up to 40\% and decreases the revenue of selfish attackers.
Industrial Internet of Things (IIoT) opens up a challenging research area towards improving secure data sharing which currently has several limitations. Primarily, the lack of inbuilt guarantees of honest behavior of participating, such as end-users or cloud behaving maliciously may result in disputes. Given such challenges, we propose a fair, accountable, and secure data sharing scheme, $\textit{FairShare}$ for IIoT. In this scheme, data collected from IoT devices are processed and stored in cloud servers with intermediate fog nodes facilitating computation. Authorized clients can access this data against some fee to make strategic decisions for improving the operational services of the IIoT system. By enabling blockchain, $\textit{FairShare}$ prevents fraudulent activities and thereby achieves fairness such that each party gets their rightful outcome in terms of data or penalty/rewards while simultaneously ensuring accountability of the services provided by the parties. Additionally, smart contracts are designed to act as a mediator during any dispute by enforcing payment settlement. Further, security and privacy of data are ensured by suitably applying cryptographic techniques like proxy re-encryption. We prove $\textit{FairShare}$ to be secure as long as at least one of the parties is honest. We validate $\textit{FairShare}$ with a theoretical overhead analysis. We also build a prototype in Ethereum to estimate performance and justify comparable results with a state-of-the-art scheme both via simulation and a realistic testbed setup. We observe an additional communication overhead of 256 bytes and a cost of deployment of 1.01 USD in Ethereum which are constant irrespective of file size.
The amount of sensitive information that service providers handle about their users has become a concerning fact in many use cases, where users have no other option but to trust that those companies will not misuse their personal information. To solve that, Self-Sovereign Identity (SSI) systems have become a hot topic of research in recent years: SSI systems allow users to manage their identities transparently. Recent solutions represent the rights of users to use services as Non-Fungible Tokens (NFTs) stored on Blockchains, and users prove possession of these rights using Zero-Knowledge Proofs (ZKPs). However, even when ZKPs do not leak any information about the rights, the NFTs are stored as public values linked to known accounts, and thus, they can be traced. In this paper, we design a native privacy-preserving NFT model for the Dusk Network Blockchain, and on top of it, we deploy Citadel: our novel full-privacy-preserving SSI system, where the rights of the users are privately stored on the Dusk Network Blockchain, and users can prove their ownership in a fully private manner.
With the rapid increase in the number of Internet of Things (IoT) devices in recent years, massive amounts of sensitive IoT data are being generated and transmitted over the Internet. Despite its growing adoption in various fields, IoT security remains a major challenge requiring further research. IoT authentication is an essential security mechanism for building trust in IoT systems. However, conventional authentication approaches use expensive cryptographic primitives that do not align with the resource-constrained nature of IoT devices. Furthermore, centralized authentication schemes have proven to be inapplicable for cross-domain authentication and do not limit the scalability of IoT networks. Recently, blockchain technology has been applied to building decentralized authentication between IoT devices. Nevertheless, most existing blockchain-based authentication approaches incur high overhead in IoT computation, storage, and energy consumption. Authentication time is another critical issue in real-time IoT systems. When numerous IoT authentication requests are transferred to the blockchain, an additional time delay is imposed, in addition to the high computational cost of the blockchain caused by the consensus mechanism. This study proposes a hybrid centralized and blockchain-based authentication architecture for IoT systems. Edge servers are deployed to provide centralized authentication for associated IoT devices. A blockchain network of centralized edge servers is then established to ensure decentralized authentication and verification of IoT devices that belong to different and heterogeneous IoT systems. Lightweight cryptographic methods are implemented to achieve efficient authentication, in which limiting the consumption of IoT resources is required. The architecture is demonstrated using a local Ethereum blockchain network. The results indicate that the proposed method achieves significant improvements in terms of computation cost, execution time, and power consumption for IoT compared with centralized and blockchain-based authentication schemes. A security analysis proves the ability of our architecture to mitigate attacks and satisfy the IoT security requirements.
Authentication and authorization constitute the essential security component, access control, for preventing unauthorized access to cloud services in mobile cloud computing (MCC) environments. Traditional centralized access control models relying on third party trust face a critical challenge due to a high trust cost and single point of failure. Blockchain can achieve the distributed trust for access control designs in a mutual untrustworthy scenario, but it also leads to expensive storage overhead. Considering the above issues, this work constructed an authentication and authorization scheme based on blockchain that can provide a dynamic update of access permissions by utilizing the smart contract. Compared with the conventional authentication scheme, the proposed scheme integrates an extra authorization function without additional computation and communication costs in the authentication phase. To improve the storage efficiency and system scalability, only one transaction is required to be stored in blockchain to record a user's access privileges on different service providers (SPs). In addition, mobile users in the proposed scheme are able to register with an arbitrary SP once and then utilize the same credential to access different SPs with different access levels. The security analysis indicates that the proposed scheme is secure under the random oracle model. The performance analysis clearly shows that the proposed scheme possesses superior computation and communication efficiencies and requires a low blockchain storage capacity for accomplishing user registration and updates.
Miodrag J. MihaljeviÄ, Milica KneĹževiÄ, Dragan UroĹĄeviÄ, Lianhai Wang ¡ 5 authors
This paper considers the problem of data access control when the subscribers are IoT devices with initialization that cannot be updated during the entire life cycle. A generic framework and a particular instance for conditional data access control within IoT are proposed. The generic framework is based on the employment of a dedicated secret key-based broadcast encryption scheme where encrypted credentials for conditional data access is available in the blockchain and encrypted data subject to conditional access are available in an off-chain source of streaming data. Reduction of the keys management overhead in comparison with a straightforward decryption keys delivery is experimentally illustrated. An instance of the proposed framework built over the Ethereum blockchain platform is developed and experimentally evaluated.
Xianhui Deng, Binyong Li, Shaowei Zhang, Liangming Deng
The blockchain-based access control mechanism (BACM) is gradually becoming an essential paradigm for solving dynamic and trusted access control problems in the open network environment. However, since the current open network environment has such features as dynamic variability and the uncertainty of user identity, most of the existing BACM cannot solve the access control problems in the current open network environment in a dynamic, flexible, proactive, efficient, and fine-grained approach. In this paper, we propose a novel BACM scheme to address such problems. Specifically, we first design a new, proactive, and fine-grained access control model, by utilizing the dynamicity and fine-grain of the attribute-based access control model, flexibility shown by the trust evaluation mechanism in evaluating the trust level of users, and proactivity shown by the game evaluation mechanism in curbing malicious users who suddenly launch malicious access requests. Second, based on the above access control model, we propose a dynamic, flexible, and proactive BACM for the current open network environment, exploiting the trustworthiness and transparency that the smart contract and the transaction mechanism in blockchain technology show during program execution. Further, a double sliding storage window is built, guaranteeing accurate data acquisition by BACM while efficiently allowing it to acquire time-sensitive data during the permission management process. Meanwhile, a pre-authorization concept is introduced to improve the efficiency and flexibility of BACM in processing access control problems. Security analysis demonstrates that our proposed BACM scheme satisfies the simple security issue and the simple availability issue. Experiments on a real user trust record dataset demonstrate the high effectiveness of the proposed BACM scheme in evaluating and deciding on access requests and the superiorities over most existing schemes in dynamicity, fine granularity, flexibility, and proactivity.
In recent years, the rapid and wide-ranging implementation of a cloud-based electronic healthcare record (EHR) storage system has shown significant advantages in effectively managing EHR for healthcare organizations and patients. However, in the cloud-based EHR storage model, the patients no longer have direct control of their EHR, whereas healthcare organizations may access the outsourced EHR whenever necessary. It may always cause severe security issues, specifically when healthcare organizations collude with the cloud service provider (CSP) to conceal any medical malpractice. Therefore, to deal with these significant concerns, we have introduced a novel blockchain based efficient tamper-proof model for EHR storage in decentralized InterPlanetary File System (IPFS) storage in the cloud - âTAC-EHRâ. The key idea of the model is that every operation involves outsourcing EHRs and integrating these EHRs into a transaction on the public blockchain provides computationally unforgeability to the outsourced EHRs. Moreover, the proposed EHR storage model can also manage batch outsourcing, i.e., numerous EHR outsourcing for multiple patients by multiple doctors simultaneously, in an effective manner. The experimental and security analysis demonstrates that the proposed blockchain based cloud-assisted EHR storage model efficiently assures intractability computationally and outperforms the existing models in terms of computational and communication overhead.
Davide Basile, Claudio Di Ciccio, Valerio Goretti, Sabrina Kirrane
Decentralization initiatives such as Solid, Digi.me, and ActivityPub aim to give data owners more control over their data and to level the playing field by enabling small companies and individuals to gain access to data, thus stimulating innovation. However, these initiatives typically use access control mechanisms that cannot verify compliance with usage conditions after access has been granted to others. In this paper, we extend the state of the art by proposing a resource governance conceptual framework, entitled ReGov, that facilitates usage control in decentralized web environments. We subsequently demonstrate how our framework can be instantiated by combining blockchain and trusted execution environments. Through blockchain technologies, we record policies expressing the usage conditions associated with resources and monitor their compliance. Our instantiation employs trusted execution environments to enforce said policies, inside data consumersâ devices. We evaluate the framework instantiation through a detailed analysis of requirments derived from a data market motivating scenario, as well as an assessment of the security, privacy, and affordability aspects of our proposal.
A non-fungible token (NFT) references a data store location, typically, using a URL or another unique identifier. At the minimum, a NFT is expected to guarantee ownership and control over the tokenised asset. However, information stored on a third party data store may be copied and stolen. We propose a solution to give control back to the information owner by storing encrypted content on the data store and providing additional security against hacks and zero day exploits. The content on our data store is never decrypted or returned to its owner for decryption during rekeying. Also, the key size in our protocol does not increase with each rekeying. With this, we reduce the synchronisation steps and maintain a bounded key size.
Most current cross-blockchain approaches focus on exchanging or transferring tokens between networks. While some concepts foster smart contract invocations across blockchains, they require multiple transactions and operate asynchronously. We present a concept enabling instant smart contract calls by creating synchronized client contracts on arbitrary blockchains. Other smart contracts can query these client contracts on the target blockchain for retrieving information without requiring cross-chain message queues. With this, we reduce the dependency of smart contracts on their host blockchain, as remote contracts become available as read-only instances. The synchronization process does not require trust in the executing intermediary since Merkle proofs based on shared state roots are utilized to guarantee correct execution. We propose a novel concept called transition proofs for efficiently proving the correctness of state updates. The prototypical implementation permits smart contract synchronization between EVM-compatible blockchains. Our evaluation shows the approachâs applicability regarding execution costs and delay. Further, we conduct a case study by synchronizing one of the largest decentralized exchanges deployed to the Ethereum network.
Efficiency is a fundamental property of any type of program, but it is even more so in the context of the programs executing on the blockchain (known as smart contracts). This is because optimizing smart contracts has direct consequences on reducing the costs of deploying and executing the contracts, as there are fees to pay related to their bytes-size and to their resource consumption (called gas). Optimizing memory usage is considered a challenging problem that, among other things, requires a precise inference of the memory locations being accessed. This is also the case for the Ethereum Virtual Machine (EVM) bytecode generated by the most-widely used compiler, \texttt{solc}, whose rather unconventional and low-level memory usage challenges automated reasoning. This paper presents a static analysis, developed at the level of the EVM bytecode generated by \texttt{solc}, that infers write memory accesses that are needless and thus can be safely removed. The application of our implementation on more than 19,000 real smart contracts has detected about 6,200 needless write accesses in less than 4 hours. Interestingly, many of these writes were involved in memory usage patterns generated by \texttt{solc} that can be greatly optimized by removing entire blocks of bytecodes. To the best of our knowledge, existing optimization tools cannot infer such needless write accesses, and hence cannot detect these inefficiencies that affect both the deployment and the execution costs of Ethereum smart contracts.
Blockchain consensus protocols have been a focus of attention since the advent of Bitcoin. Although classic distributed consensus algorithms made significant contributions to the development of blockchain consensus protocols, there are still many issues to be resolved due to the complexity and diversity of the blockchain. In this survey, we summarize the state-of-the-art blockchain consensus protocols. We first introduce the theoretical basis, models, and challenges of blockchain consensus protocols. Then, we present the existing blockchain protocols in the categories of proof-based protocols, committee-based protocols, and other miscellaneous protocols. Finally, we analyze their performance and discuss future research directions by comparing existing protocols.
AndrÊ Augusto, Rafael Belchior, Imre Kocsis, GÜnczy Låszló ¡ 6 authors
The last few years have seen a steep increase in blockchain interoperability research. Most solutions connect public blockchains; hence, the main cross-chain use case is token transfer. By-design platform transparency, tamper-resistance, and auditability make blockchains an infrastructure candidate for Central Bank Digital Currencies (CBDCs), but bridging CBDCs is an important missing piece in general. In this paper, we leverage an asset transfer protocol, ODAP/SATP, to define an extendable and dependable blockchain interoperability middleware that can bridge CBDC from Hyperledger Fabric to EVM-based permissioned blockchains. The key interoperation enabler in the solution is a shared asset definition enforced by both sides of the bridge, accompanied by a mapping between Fabric Identities and Ethereum addresses for Identity management. We implement our design for the CBDC use case utilizing Hyperledger Cactus. Through a preliminary performance evaluation, we show that the underlying ledgers heavily influence the latency of the solution, not the bridging components.
Abstract With the rapid increment of the demand for data sharing among parties, data is considered a cornerstone component to provide value in the big data environment. Concerns regarding sharing data security have impeded the development of crossâdomain data interaction. Therefore, an access control model for data security sharing crossâdomain is proposed, FabricâABAC, that is based on Hyperledger Fabric and Attributeâbased Access Control (ABAC). In order to solve the data security challenges caused by a trusted central organization implementation, a distributed environment is constructed that consists of stakeholders among parties. The unified attribute model is designed for multiâenvironment combined with smart contracts. FabricâABAC realizes multiâlevel, fineâgrained, and auditable access control, enabling data security through automatic permission verification. Considering the ledger is visible to all participants in consortium blockchain, it is necessary to protect the confidentiality of sensitive data. Thus, Proxy ReâEncryption (PRE), which is implemented by smart contracts, is adopted in the scheme to realize the ciphertext interaction without the third party. The security of PRE and the access control model used in FabricâABAC is discussed to show that a secure environment for data sharing is provided. Moreover, the completeness of the implementation and effectiveness of the system performance in the multiâdomain environment is demonstrated in the experimental results.
Taotao Wang, Zibin Lin, Shengli Zhang, Long Shi ¡ 6 authors
A decentralized identity system that can provide users with self-sovereign digital identities to facilitate complete control over their own data is paramount to Web 3.0. The account system on blockchain is an ideal archetype for realizing Web 3.0 decentralized identity. However, a disadvantage of such completely anonymous identity system is that users can create multiple accounts without authentication to obfuscate their activities on the blockchain. In particular, the current anonymous blockchain account system cannot accurately register the social relationships and interactions between real human users, given the amorphous mappings between users and blockchain identities. This work proposes zkBID, a zero-knowledge blockchain-account-based Web 3.0 decentralized identity scheme, to overcome endemic mistrust in blockchain account systems. zkBID links souls (blockchain accounts) to humans (users' personhood credentials) in a one-to-one manner to truly reflect the social relationships and interactions between humans on the blockchain. zkBID conceals the one-to-one relationships between blockchain accounts and users' personhood credentials for privacy protection using zero-knowledge proofs and linkable ring signatures. Thus, with zkBID, the users' blockchain accounts are credibly anonymous. Importantly, zkBID is fully decentralized: all user-related data are generated by users and verified by smart contracts on the blockchain. We implemented zkBID and built a blockchain test network for evaluation purposes. Our tests demonstrate the effectiveness of zkBID and suggest proper ways to configure zkBID system parameters.
Open access
3 source records
cs.CR
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Graham Cormode, Marcel DallâAgnol, Tom Gur, Christopher W. Hickey
Streaming interactive proofs (SIPs) enable a space-bounded algorithm with one-pass access to a massive stream of data to verify a computation that requires large space, by communicating with a powerful but untrusted prover. This work initiates the study of zero-knowledge proofs for data streams. We define the notion of zero-knowledge in the streaming setting and construct zero-knowledge SIPs for the two main algorithmic building blocks in the streaming interactive proofs literature: the sumcheck and polynomial evaluation protocols. To the best of our knowledge all known streaming interactive proofs are based on either of these tools, and indeed, this allows us to obtain zero-knowledge SIPs for central streaming problems such as index, point and range queries, median, frequency moments, and inner product. Our protocols are efficient in terms of time and space, as well as communication: the verifier algorithm's space complexity is $\mathrm{polylog}(n)$ and, after a non-interactive setup that uses a random string of near-linear length, the remaining parameters are $n^{o(1)}$. En route, we develop an algorithmic toolkit for designing zero-knowledge data stream protocols, consisting of an algebraic streaming commitment protocol and a temporal commitment protocol.Our analyses rely on delicate algebraic and information-theoretic arguments and reductions from average-case communication complexity.
Damiano Di Francesco Maesa, Andrea Lisi, Paolo Mori, Laura Ricci ¡ 5 authors
Recent years have witnessed, especially in Europe, a shift aimed at bringing users back at the center of digital systems. This has driven innovation towards the affirmation of decentralized systems, in line with the Self Sovereign Identity paradigm. User control over the consumption and disclosure of their data is a key topic of such drive. In this paper we show how it is possible to apply this increasingly popular concept to a traditionally centralized and opaque digital process: Access Control systems. To this aim we expand the XACML standard for Attribute Based Access Control systems with the novel concept of private attributes, i.e. attributes whose values should not be disclosed while still contributing to a policy evaluation result after user consent. Basing our proposal on blockchain systems, we show how to leverage smart contracts and zero knowledge proofs to allow for transparent policies evaluation without disclosing the value of such sensible attributes. Beside formalizing our goals, presenting the system architecture, and discussing its advantages and drawbacks with respect to the traditional model, we provide a reference example to show our proposal innovative capabilities and provide a prototype experimental evaluation to prove its feasibility.
Xin Liu, Xiaofen Tu, Dan Luo, Gang Xu ¡ 6 authors
In recent years, with the development of information security, secure multi-party computation has gradually become a research hotspot in the field of privacy protection. The intersection and union computation of graphs is an important branch of secure computing geometry. At present, the intersection and union of graphs are almost designed under the semi-honest model, and few solutions are proposed under the malicious model. However, the solution under the malicious model is more secure and has important theoretical and practical significance. In this paper, the possible malicious behaviors of computing the intersection and union of graphs are analyzed. Using the Lifted-ElGamal threshold cryptosystem and zero-knowledge proof method, the secure multi-party computation algorithm of graphsâ intersection and union under the malicious model is designed. The real/ideal model paradigm is used to prove the security of the algorithm, the efficiency of the algorithm is analyzed in detail, and the feasibility is verified through experiment.
Several emerging areas, such as sensor networks, the Internet of Things (IoT), and distributed networks are gaining traction where resource-constrained devices communicate by sharing privacy-preserving information. Due to heavy cryptographic components, standard cryptographic algorithms do not fit these IoT devices. In this article, we propose an efficient zero-knowledge blockchain-based privacy-preserving decentralized healthcare finance system that is suitable for lightweight computer devices. The proposed design mainly focuses on noninteractive zero-knowledge proof, which substantially reduces the cost of communication between two devices. We explain the system framework and its use case for a healthcare financial system at a micro-level. However, it can also be extended easily to more general financial systems. Our system framework is efficient and lightweight, using more efficient zero-knowledge-based proofs; validation of the transactions is done in milliseconds. As an advancement to our work, the proposed healthcare financial system for lightweight computer devices is also auditable without leaking any extra information than required.
Today, digital identity management for individuals is either inconvenient and error-prone or creates undesirable lock-in effects and violates privacy and security expectations. These shortcomings inhibit the digital transformation in general and seem particularly concerning in the context of novel applications such as access control for decentralized autonomous organizations and identification in the Metaverse. Decentralized or self-sovereign identity (SSI) aims to offer a solution to this dilemma by empowering individuals to manage their digital identity through machine-verifiable attestations stored in a "digital wallet" application on their edge devices. However, when presented to a relying party, these attestations typically reveal more attributes than required and allow tracking end users' activities. Several academic works and practical solutions exist to reduce or avoid such excessive information disclosure, from simple selective disclosure to data-minimizing anonymous credentials based on zero-knowledge proofs (ZKPs). We first demonstrate that the SSI solutions that are currently built with anonymous credentials still lack essential features such as scalable revocation, certificate chaining, and integration with secure elements. We then argue that general-purpose ZKPs in the form of zk-SNARKs can appropriately address these pressing challenges. We describe our implementation and conduct performance tests on different edge devices to illustrate that the performance of zk-SNARK-based anonymous credentials is already practical. We also discuss further advantages that general-purpose ZKPs can easily provide for digital wallets, for instance, to create "designated verifier presentations" that facilitate new design options for digital identity infrastructures that previously were not accessible because of the threat of man-in-the-middle attacks.
Despite the maturity of cloud services (e.g., outsourcing of computational tasks), a number of operational challenges remain. For example, how do we ensure trust between outsourcers and workers in a zero-trust environment? While a number of blockchain-based solutions that eliminate the reliance on trusted third parties have been presented, many of these existing approaches do not achieve robust fairness and/or support compatibility with other systems. In this paper, we propose an efficient fair payment system using blockchain (EFPB), designed to achieve robust fairness and compatibility. Specifically, EFPB comprises a number of cryptographic building blocks, mainly: one-way accumulator (RSA-based construction), stealth address and symmetric encryption. We then evaluate the performance of EFPB to demonstrate that it is more efficient and low-cost than other competing schemes, as well as presenting a comparative summary of functionalities.
Currently, smart homes rely heavily on wireless sensor networks (WSNs), which typically consist of wireless sensor nodes with limited resources and are scattered throughout the network. This topology makes them vulnerable to packet sniffing, spoofing, and other malicious attacks, which can result in the leakage of private data collected by devices. Additionally, managing the device key for the entire system becomes difficult as more devices are added. Moreover, the centralization of current cloud service management in smart home systems poses a serious single-point-of-failure problem, and the private data of cloud outsourcing cannot receive strict privacy supervision, ultimately relying entirely on the trust of enterprises. To address these issues, this paper proposes using a consortium blockchain and InterPlanetary File System (IPFS) instead of the existing centralized structure. An improved pairing-free certificateless aggregated signature(CLAS) scheme ensures the security of message authentication and solves the device key management problem. Our scheme reduces the computational and communication overheads at the device side by 50% and 25%, respectively, compared with existing schemes in WSNs. The overall computational overhead is also reduced by 28.6%, making it more suitable for smart home scenarios. Additionally, we use an auditing method based on Merkle root hash verification to ensure the reliability of data storage in IPFS.
Internet of Medical Things (IoMT) plays an essential role in collecting and managing personal medical data. In recent years, blockchain technology has put power in traditional IoMT systems for data sharing between different medical institutions and improved the utilization of medical data. However, some problems in the information transfer process between wireless medical devices and mobile medical apps, such as information leakage and privacy disclosure. This paper first designs a cross-device key agreement model for blockchain-enabled IoMT. This model can establish a key agreement mechanism for secure medical data sharing. Meanwhile, a certificateless authenticated key agreement (KA) protocol has been proposed to strengthen the information transfer security in the cross-device key agreement model. The proposed KA protocol only requires one exchange of messages between the two parties, which can improve the protocol execution efficiency. Then, any unauthorized tampering of the transmitted signed message sent by the sender can be detected by the receiver, so this can guarantee the success of the establishment of a session key between the strange entities. The blockchain ledger can ensure that the medical data cannot be tampered with, and the certificateless mechanism can weaken the key escrow problem. Moreover, the security proof and performance analysis are given, which show that the proposed model and KA protocol are more secure and efficient than other schemes in similar literature.