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2021-05-25
Ajorlou, Amir, Abbasfar, Aliazam.  2020.  An Optimized Structure of State Channel Network to Improve Scalability of Blockchain Algorithms. 2020 17th International ISC Conference on Information Security and Cryptology (ISCISC). :73—76.
Nowadays, blockchain is very common and widely used in various fields. The properties of blockchain-based algorithms such as being decentralized and uncontrolled by institutions and governments, are the main reasons that has attracted many applications. The security and the scalability limitations are the main challenges for the development of these systems. Using second layer network is one of the various methods proposed to improve the scalability of these systems. This network can increase the total number of transactions per second by creating extra channels between the nodes that operate in a different layer not obligated to be on consensus ledger. In this paper, the optimal structure for the second layer network has been presented. In the proposed structure we try to distribute the parameters of the second layer network as symmetrically as possible. To prove the optimality of this structure we first introduce the maximum scalability bound, and then calculate it for the proposed structure. This paper will show how the second layer method can improve the scalability without any information about the rate of transactions between nodes.
2021-03-09
Soni, D. K., Sharma, H., Bhushan, B., Sharma, N., Kaushik, I..  2020.  Security Issues Seclusion in Bitcoin System. 2020 IEEE 9th International Conference on Communication Systems and Network Technologies (CSNT). :223—229.

In the dawn of crypto-currencies the most talked currency is Bitcoin. Bitcoin is widely flourished digital currency and an exchange trading commodity implementing peer-to-peer payment network. No central athourity exists in Bitcoin. The users in network or pool of bitcoin need not to use real names, rather they use pseudo names for managing and verifying transactions. Due to the use of pseudo names bitcoin is apprehended to provide anonymity. However, the most transparent payment network is what bitcoin is. Here all the transactions are publicly open. To furnish wholeness and put a stop to double-spending, Blockchain is used, which actually works as a ledger for management of Bitcoins. Blockchain can be misused to monitor flow of bitcoins among multiple transactions. When data from external sources is amalgamated with insinuation acquired from the Blockchain, it may result to reveal user's identity and profile. In this way the activity of user may be traced to an extent to fraud that user. Along with the popularity of Bitcoins the number of adversarial attacks has also gain pace. All these activities are meant to exploit anonymity and privacy in Bitcoin. These acivities result in loss of bitcoins and unlawful profit to attackers. Here in this paper we tried to present analysis of major attacks such as malicious attack, greater than 52% attacks and block withholding attack. Also this paper aims to present analysis and improvements in Bitcoin's anonymity and privacy.

Badawi, E., Jourdan, G.-V., Bochmann, G., Onut, I.-V..  2020.  An Automatic Detection and Analysis of the Bitcoin Generator Scam. 2020 IEEE European Symposium on Security and Privacy Workshops (EuroS PW). :407—416.

We investigate what we call the "Bitcoin Generator Scam" (BGS), a simple system in which the scammers promise to "generate" new bitcoins using the ones that were sent to them. A typical offer will suggest that, for a small fee, one could receive within minutes twice the amount of bitcoins submitted. BGS is clearly not a very sophisticated attack. The modus operandi is simply to put up some web page on which to find the address to send the money and wait for the payback. The pages are then indexed by search engines, and ready to find for victims looking for free bitcoins. We describe here a generic system to find and analyze scams such as BGS. We have trained a classifier to detect these pages, and we have a crawler searching for instances using a series of search engines. We then monitor the instances that we find to trace payments and bitcoin addresses that are being used over time. Unlike most bitcoin-based scam monitoring systems, we do not rely on analyzing transactions on the blockchain to find scam instances. Instead, we proactively find these instances through the web pages advertising the scam. Thus our system is able to find addresses with very few transactions, or even none at all. Indeed, over half of the addresses that have eventually received funds were detected before receiving any transactions. The data for this paper was collected over four months, from November 2019 to February 2020. We have found more than 1,300 addresses directly associated with the scam, hosted on over 500 domains. Overall, these addresses have received (at least) over 5 million USD to the scam, with an average of 47.3 USD per transaction.

2021-02-10
Varlioglu, S., Gonen, B., Ozer, M., Bastug, M..  2020.  Is Cryptojacking Dead After Coinhive Shutdown? 2020 3rd International Conference on Information and Computer Technologies (ICICT). :385—389.
Cryptojacking is the exploitation of victims' computer resources to mine for cryptocurrency using malicious scripts. It had become popular after 2017 when attackers started to exploit legal mining scripts, especially Coinhive scripts. Coinhive was actually a legal mining service that provided scripts and servers for in-browser mining activities. Nevertheless, over 10 million web users had been victims every month before the Coinhive shutdown that happened in Mar 2019. This paper explores the new era of the cryptojacking world after Coinhive discontinued its service. We aimed to see whether and how attackers continue cryptojacking, generate new malicious scripts, and developed new methods. We used a capable cryptojacking detector named CMTracker that proposed by Hong et al. in 2018. We automatically and manually examined 2770 websites that had been detected by CMTracker before the Coinhive shutdown. The results revealed that 99% of sites no longer continue cryptojacking. 1% of websites still run 8 unique mining scripts. By tracking these mining scripts, we detected 632 unique cryptojacking websites. Moreover, open-source investigations (OSINT) demonstrated that attackers still use the same methods. Therefore, we listed the typical patterns of cryptojacking. We concluded that cryptojacking is not dead after the Coinhive shutdown. It is still alive, but not as attractive as it used to be.
Tizio, G. Di, Ngo, C. Nam.  2020.  Are You a Favorite Target For Cryptojacking? A Case-Control Study On The Cryptojacking Ecosystem 2020 IEEE European Symposium on Security and Privacy Workshops (EuroS PW). :515—520.
Illicitly hijacking visitors' computational resources for mining cryptocurrency via compromised websites is a consolidated activity.Previous works mainly focused on large-scale analysis of the cryptojacking ecosystem, technical means to detect browser-based mining as well as economic incentives of cryptojacking. So far, no one has studied if certain technical characteristics of a website can increase (decrease) the likelihood of being compromised for cryptojacking campaigns.In this paper, we propose to address this unanswered question by conducting a case-control study with cryptojacking websites obtained crawling the web using Minesweeper. Our preliminary analysis shows some association for certain website characteristics, however, the results obtained are not statistically significant. Thus, more data must be collected and further analysis must be conducted to obtain a better insight into the impact of these relations.
2021-02-08
Noel, M. D., Waziri, O. V., Abdulhamid, M. S., Ojeniyi, A. J., Okoro, M. U..  2020.  Comparative Analysis of Classical and Post-quantum Digital Signature Algorithms used in Bitcoin Transactions. 2020 2nd International Conference on Computer and Information Sciences (ICCIS). :1–6.

The use of public key cryptosystems ranges from securely encrypting bitcoin transactions and creating digital signatures for non-repudiation. The cryptographic systems security of public key depends on the complexity in solving mathematical problems. Quantum computers pose a threat to the current day algorithms used. This research presents analysis of two Hash-based Signature Schemes (MSS and W-OTS) and provides a comparative analysis of them. The comparisons are based on their efficiency as regards to their key generation, signature generation and verification time. These algorithms are compared with two classical algorithms (RSA and ECDSA) used in bitcoin transaction security. The results as shown in table II indicates that RSA key generation takes 0.2012s, signature generation takes 0.0778s and signature verification is 0.0040s. ECDSA key generation is 0.1378s, signature generation takes 0.0187s, and verification time for the signature is 0.0164s. The W-OTS key generation is 0.002s. To generate a signature in W-OTS, it takes 0.001s and verification time for the signature is 0.0002s. Lastly MSS Key generation, signature generation and verification has high values which are 16.290s, 17.474s, and 13.494s respectively. Based on the results, W-OTS is recommended for bitcoin transaction security because of its efficiency and ability to resist quantum computer attacks on the bitcoin network.

2020-12-01
Craggs, B., Rashid, A..  2019.  Trust Beyond Computation Alone: Human Aspects of Trust in Blockchain Technologies. 2019 IEEE/ACM 41st International Conference on Software Engineering: Software Engineering in Society (ICSE-SEIS). :21—30.

Blockchains - with their inherent properties of transaction transparency, distributed consensus, immutability and cryptographic verifiability - are increasingly seen as a means to underpin innovative products and services in a range of sectors from finance through to energy and healthcare. Discussions, too often, make assertions that the trustless nature of blockchain technologies enables and actively promotes their suitability - there being no need to trust third parties or centralised control. Yet humans need to be able to trust systems, and others with whom the system enables transactions. In this paper, we highlight that understanding this need for trust is critical for the development of blockchain-based systems. Through an online study with 125 users of the most well-known of blockchain based systems - the cryptocurrency Bitcoin - we uncover that human and institutional aspects of trust are pervasive. Our analysis highlights that, when designing future blockchain-based technologies, we ought to not only consider computational trust but also the wider eco-system, how trust plays a part in users engaging/disengaging with such eco-systems and where design choices impact upon trust. From this, we distill a set of guidelines for software engineers developing blockchain-based systems for societal applications.

2020-09-21
Takahashi, Hironao, Lakhani, Uzair.  2019.  Multiple Layered Security Analyses Method for Cryptocurrency Exchange Servicers. 2019 IEEE 8th Global Conference on Consumer Electronics (GCCE). :71–73.
Internet is a common method of trading business today. The usage of cryptocurrencies has increased these days and it has become a trend to utilize them. Cryptocurrency exchange servicers provide different smartphone apps that unfortunately may become the target of malicious attacks. This paper focuses on how it achieves highest security and proposes the multiple layered security analyses method for cryptocurrency exchange servicers.
2020-09-04
Ichsani, Yuditha, Deyani, Resisca Audia, Bahaweres, Rizal Broer.  2019.  The Cryptocurrency Simulation using Elliptic Curve Cryptography Algorithm in Mining Process from Normal, Failed, and Fake Bitcoin Transactions. 2019 7th International Conference on Cyber and IT Service Management (CITSM). 7:1—8.
On each cryptocurrency transaction, a high-level security is needed to protect user data as well as data on the transaction. At this stage, it takes the appropriate algorithm in securing transactions with more efficient processing time. The Elliptic Curve Cryptography (ECC) is one of the cryptography algorithms which has high-level security, and ECC is often compared with the Rivest, Shamir, and Adleman (RSA) algorithm because it has a security level that is almost the same but has some differences that make ECC is superior compared to the RSA algorithm, so that the ECC algorithm can optimize cryptocurrency security in the transaction process. The purpose of this study is to simulate the bitcoin transactions using cryptography algorithms. This study uses the ECC algorithm as the algorithm ECDH and ECDSA key exchange as the algorithm for signing and verifying. The comparison results of ECC and RSA processing time is 1:25, so the ECC is more efficient. The total processing time of ECC is 0,006 seconds and RSA is 0,152 seconds. The researcher succeeded to implement the ECC algorithm as securing algorithms in mining process of 3 scenarios, normal, failed, and fake bitcoin transactions.
Elliott, Sean.  2019.  Nash Equilibrium of Multiple, Non-Uniform Bitcoin Block Withholding Attackers. 2019 2nd International Conference on Data Intelligence and Security (ICDIS). :144—151.
This research analyzes a seemingly malicious behavior known as a block withholding (BWH) attack between pools of cryptocurrency miners in Bitcoin-like systems featuring blockchain distributed databases. This work updates and builds on a seminal paper, The Miner's Dilemma, which studied a simplified scenario and showed that a BWH attack can be rational behavior that is profitable for the attacker. The new research presented here provides an in-depth profit analysis of a more complex and realistic BWH attack scenario, which includes mutual attacks between multiple, non-uniform Bitcoin mining pools. As a result of mathematical analysis and MATLAB modeling, this paper illustrates the Nash equilibrium conditions of a system of independent mining pools with varied mining rates and computes the equilibrium rates of mutual BWH attack. The analysis method quantifies the additional profit the largest pools extract from the system at the expense of the smaller pools. The results indicate that while the presence of BWH is a net negative for smaller pools, they must participate in BWH to maximize their remaining profits, and the results quantify the attack rates the smaller pools must maintain. Also, the smallest pools maximize profit by not attacking at all-that is, retaliation is not a rational move for them.
2020-07-10
Javed Butt, Usman, Abbod, Maysam, Lors, Anzor, Jahankhani, Hamid, Jamal, Arshad, Kumar, Arvind.  2019.  Ransomware Threat and its Impact on SCADA. 2019 IEEE 12th International Conference on Global Security, Safety and Sustainability (ICGS3). :205—212.
Modern cybercrimes have exponentially grown over the last one decade. Ransomware is one of the types of malware which is the result of sophisticated attempt to compromise the modern computer systems. The governments and large corporations are investing heavily to combat this cyber threat against their critical infrastructure. It has been observed that over the last few years that Industrial Control Systems (ICS) have become the main target of Ransomware due to the sensitive operations involved in the day to day processes of these industries. As the technology is evolving, more and more traditional industrial systems are replaced with advanced industry methods involving advanced technologies such as Internet of Things (IoT). These technology shift help improve business productivity and keep the company's global competitive in an overflowing competitive market. However, the systems involved need secure measures to protect integrity and availability which will help avoid any malfunctioning to their operations due to the cyber-attacks. There have been several cyber-attack incidents on healthcare, pharmaceutical, water cleaning and energy sector. These ICS' s are operated by remote control facilities and variety of other devices such as programmable logic controllers (PLC) and sensors to make a network. Cyber criminals are exploring vulnerabilities in the design of these ICS's to take the command and control of these systems and disrupt daily operations until ransomware is paid. This paper will provide critical analysis of the impact of Ransomware threat on SCADA systems.
Yulianto, Arief Dwi, Sukarno, Parman, Warrdana, Aulia Arif, Makky, Muhammad Al.  2019.  Mitigation of Cryptojacking Attacks Using Taint Analysis. 2019 4th International Conference on Information Technology, Information Systems and Electrical Engineering (ICITISEE). :234—238.

Cryptojacking (also called malicious cryptocurrency mining or cryptomining) is a new threat model using CPU resources covertly “mining” a cryptocurrency in the browser. The impact is a surge in CPU Usage and slows the system performance. In this research, in-browsercryptojacking mitigation has been built as an extension in Google Chrome using Taint analysis method. The method used in this research is attack modeling with abuse case using the Man-In-The-Middle (MITM) attack as a testing for mitigation. The proposed model is designed so that users will be notified if a cryptojacking attack occurs. Hence, the user is able to check the script characteristics that run on the website background. The results of this research show that the taint analysis is a promising method to mitigate cryptojacking attacks. From 100 random sample websites, the taint analysis method can detect 19 websites that are infcted by cryptojacking.

Tahir, Rashid, Durrani, Sultan, Ahmed, Faizan, Saeed, Hammas, Zaffar, Fareed, Ilyas, Saqib.  2019.  The Browsers Strike Back: Countering Cryptojacking and Parasitic Miners on the Web. IEEE INFOCOM 2019 - IEEE Conference on Computer Communications. :703—711.

With the recent boom in the cryptocurrency market, hackers have been on the lookout to find novel ways of commandeering users' machine for covert and stealthy mining operations. In an attempt to expose such under-the-hood practices, this paper explores the issue of browser cryptojacking, whereby miners are secretly deployed inside browser code without the knowledge of the user. To this end, we analyze the top 50k websites from Alexa and find a noticeable percentage of sites that are indulging in this exploitative exercise often using heavily obfuscated code. Furthermore, mining prevention plug-ins, such as NoMiner, fail to flag such cleverly concealed instances. Hence, we propose a machine learning solution based on hardware-assisted profiling of browser code in real-time. A fine-grained micro-architectural footprint allows us to classify mining applications with \textbackslashtextgreater99% accuracy and even flags them if the mining code has been heavily obfuscated or encrypted. We build our own browser extension and show that it outperforms other plug-ins. The proposed design has negligible overhead on the user's machine and works for all standard off-the-shelf CPUs.

2020-06-22
Noel, Moses Dogonyaro, Waziri, Onomza Victor, Abdulhamid, Muhammad Shafii, Ojeniyi, Adebayo Joseph.  2019.  Stateful Hash-based Digital Signature Schemes for Bitcoin Cryptocurrency. 2019 15th International Conference on Electronics, Computer and Computation (ICECCO). :1–6.
Modern computing devices use classical algorithms such as Rivest Shamir Adleman (RSA) and Elliptic Curve Digital Signature Algorithm (ECDSA) for their security. The securities of these algorithms relied on the problem and difficulty of integer factorization and also calculating the Discrete Logarithm Problems. With the introduction of quantum computers, recent research is focusing on developing alternative algorithms which are supposed to withstand attacks from quantum computers. One of such alternatives is the Hash-based Digital Signature Schemes. Chosen hash-based signature schemes over classical algorithms is because their security is on the hash function used and that they are metaheuristic in nature. This research work presents basic analysis and the background understanding of Stateful Hash-based Signature Schemes, particularly the Lamport One-Time Signature Scheme, Winternitz One-Time Signature Scheme, and the Merkle Signature Scheme. The three schemes selected are stateful, hence has common features and are few-time hash-based signature schemes. The selected Stateful Hash-based Digital Signature Schemes were analyzed based on their respective key generation, signature generation, signature verification, and their security levels. Practical working examples were given for better understanding. With the analyses, Merkle Signature Scheme proves to be the best candidate to be used in the Bitcoin Proof of Work protocol because of its security and its advantage of signing many messages.
2020-04-06
Erfani, Shervin, Ahmadi, Majid.  2019.  Bitcoin Security Reference Model: An Implementation Platform. 2019 International Symposium on Signals, Circuits and Systems (ISSCS). :1–5.
Bitcoin is a cryptocurrency which acts as an application protocol that works on top of the IP protocol. This paper focuses on distinct Bitcoin security features, including security services, mechanisms, and algorithms. Further, we propose a well-defined security functional architecture to minimize security risks. The security features and requirements of Bitcoin have been structured in layers.
2020-03-30
Khan, Abdul Ghaffar, Zahid, Amjad Hussain, Hussain, Muzammil, Riaz, Usama.  2019.  Security Of Cryptocurrency Using Hardware Wallet And QR Code. 2019 International Conference on Innovative Computing (ICIC). :1–10.
Today, the privacy and the security of any organization are the key requirement, the digital online transaction of money or coins also needed a certain level of security not only during the broadcasting of the transaction but before the sending of the transaction. In this research paper we proposed and implemented a cryptocurrency (Bitcoin) wallet for the android operating system, by using the QR code-based android application and a secure private key storage (Cold Wallet). Two android applications have been implemented one of them is called cold wallet and the other one is hot wallet. Cold wallet (offline) is to store and generate the private key addresses for secure transaction confirmation and the hot wallet is used to send bitcoin to the network. Hot wallet application gives facility to the user view history of performed transactions, to send and compose a new bitcoin transaction, receive bitcoin, sign it and send it to the network. By using the process of cross QR code scanning of the hot and cold wallet to the identification, validation and authentication of the user made it secure.
2020-03-04
Shahsavari, Yahya, Zhang, Kaiwen, Talhi, Chamseddine.  2019.  A Theoretical Model for Fork Analysis in the Bitcoin Network. 2019 IEEE International Conference on Blockchain (Blockchain). :237–244.

Blockchain networks which employ Proof-of-Work in their consensus mechanism may face inconsistencies in the form of forks. These forks are usually resolved through the application of block selection rules (such as the Nakamoto consensus). In this paper, we investigate the cause and length of forks for the Bitcoin network. We develop theoretical formulas which model the Bitcoin consensus and network protocols, based on an Erdös-Rényi random graph construction of the overlay network of peers. Our theoretical model addresses the effect of key parameters on the fork occurrence probability, such as block propagation delay, network bandwidth, and block size. We also leverage this model to estimate the weight of fork branches. Our model is implemented using the network simulator OMNET++ and validated by historical Bitcoin data. We show that under current conditions, Bitcoin will not benefit from increasing the number of connections per node.

2020-02-10
Taher, Kazi Abu, Nahar, Tahmin, Hossain, Syed Akhter.  2019.  Enhanced Cryptocurrency Security by Time-Based Token Multi-Factor Authentication Algorithm. 2019 International Conference on Robotics,Electrical and Signal Processing Techniques (ICREST). :308–312.
A noble multi-factor authentication (MFA) algorithm is developed for the security enhancement of the Cryptocurrency (CR). The main goal of MFA is to set up extra layer of safeguard while seeking access to a targets such as physical location, computing device, network or database. MFA security scheme requires more than one method for the validation from commutative family of credentials to verify the user for a transaction. MFA can reduce the risk of using single level password authentication by introducing additional factors of authentication. MFA can prevent hackers from gaining access to a particular account even if the password is compromised. The superfluous layer of security introduced by MFA offers additional security to a user. MFA is implemented by using time-based onetime password (TOTP) technique. For logging to any entity with MFA enabled, the user first needs username and password, as a second factor, the user then needs the MFA token to virtually generate a TOTP. It is found that MFA can provide a better means of secured transaction of CR.
2020-01-21
Soltani, Reza, Nguyen, Uyen Trang, An, Aijun.  2019.  Practical Key Recovery Model for Self-Sovereign Identity Based Digital Wallets. 2019 IEEE Intl Conf on Dependable, Autonomic and Secure Computing, Intl Conf on Pervasive Intelligence and Computing, Intl Conf on Cloud and Big Data Computing, Intl Conf on Cyber Science and Technology Congress (DASC/PiCom/CBDCom/CyberSciTech). :320–325.
Recent years have seen an increased interest in digital wallets for a multitude of use cases including online banking, cryptocurrency, and digital identity management. Digital wallets play a pivotal role in the secure management of cryptographic keys and credentials, and for providing certain identity management services. In this paper, we examine a proof-of-concept digital wallet in the context of Self-Sovereign Identity and provide a practical decentralized key recovery solution using Shamir's secret sharing scheme and Hyperledger Indy distributed ledger technology.
2019-12-16
Tsabary, Itay, Eyal, Ittay.  2018.  The Gap Game. Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security. :713-728.

Blockchain-based cryptocurrencies secure a decentralized consensus protocol by incentives. The protocol participants, called miners, generate (mine) a series of blocks, each containing monetary transactions created by system users. As incentive for participation, miners receive newly minted currency and transaction fees paid by transaction creators. Blockchain bandwidth limits lead users to pay increasing fees in order to prioritize their transactions. However, most prior work focused on models where fees are negligible. In a notable exception, Carlsten et al. [17] postulated that if incentives come only from fees then a mining gap would form\textasciitilde— miners would avoid mining when the available fees are insufficient. In this work, we analyze cryptocurrency security in realistic settings, taking into account all elements of expenses and rewards. To study when gaps form, we analyze the system as a game we call the gap game. We analyze the game with a combination of symbolic and numeric analysis tools in a wide range of scenarios. Our analysis confirms Carlsten et al.'s postulate; indeed, we show that gaps form well before fees are the only incentive, and analyze the implications on security. Perhaps surprisingly, we show that different miners choose different gap sizes to optimize their utility, even when their operating costs are identical. Alarmingly, we see that the system incentivizes large miner coalitions, reducing system decentralization. We describe the required conditions to avoid the incentive misalignment, providing guidelines for future cryptocurrency design.

2019-12-02
Ibarra, Jaime, Javed Butt, Usman, Do, Anh, Jahankhani, Hamid, Jamal, Arshad.  2019.  Ransomware Impact to SCADA Systems and its Scope to Critical Infrastructure. 2019 IEEE 12th International Conference on Global Security, Safety and Sustainability (ICGS3). :1–12.
SCADA systems are being constantly migrated to modern information and communication technologies (ICT) -based systems named cyber-physical systems. Unfortunately, this allows attackers to execute exploitation techniques into these architectures. In addition, ransomware insertion is nowadays the most popular attacking vector because it denies the availability of critical files and systems until attackers receive the demanded ransom. In this paper, it is analysed the risk impact of ransomware insertion into SCADA systems and it is suggested countermeasures addressed to the protection of SCADA systems and its components to reduce the impact of ransomware insertion.
2019-11-26
Acharjamayum, Irani, Patgiri, Ripon, Devi, Dhruwajita.  2018.  Blockchain: A Tale of Peer to Peer Security. 2018 IEEE Symposium Series on Computational Intelligence (SSCI). :609-617.

The underlying or core technology of Bitcoin cryptocurrency has become a blessing for human being in this era. Everything is gradually changing to digitization in this today's epoch. Bitcoin creates virtual money using Blockchain that's become popular over the world. Blockchain is a shared public ledger, and it includes all transactions which are confirmed. It is almost impossible to crack the hidden information in the blocks of the Blockchain. However, there are certain security and technical challenges like scalability, privacy leakage, selfish mining, etc. which hampers the wide application of Blockchain. In this paper, we briefly discuss this emerging technology namely Blockchain. In addition, we extrapolate in-depth insight on Blockchain technology.

2019-06-28
Hazari, S. S., Mahmoud, Q. H..  2019.  A Parallel Proof of Work to Improve Transaction Speed and Scalability in Blockchain Systems. 2019 IEEE 9th Annual Computing and Communication Workshop and Conference (CCWC). :0916-0921.

A blockchain is a distributed ledger forming a distributed consensus on a history of transactions, and is the underlying technology for the Bitcoin cryptocurrency. However, its applications are far beyond the financial sector. The transaction verification process for cryptocurrencies is much slower than traditional digital transaction systems. One approach to increase transaction speed and scalability is to identify a solution that offers faster Proof of Work. In this paper, we propose a method for accelerating the process of Proof of Work based on parallel mining rather than solo mining. The goal is to ensure that no more than two or more miners put the same effort into solving a specific block. The proposed method includes a process for selection of a manager, distribution of work and a reward system. This method has been implemented in a test environment that contains all the characteristics needed to perform Proof of Work for Bitcoin and has been tested, using a variety of case scenarios, by varying the difficulty level and number of validators. Preliminary results show improvement in the scalability of Proof of Work up to 34% compared to the current system.

2019-04-01
Li, Z., Liao, Q..  2018.  CAPTCHA: Machine or Human Solvers? A Game-Theoretical Analysis 2018 5th IEEE International Conference on Cyber Security and Cloud Computing (CSCloud)/2018 4th IEEE International Conference on Edge Computing and Scalable Cloud (EdgeCom). :18–23.
CAPTCHAs have become an ubiquitous defense used to protect open web resources from being exploited at scale. Traditionally, attackers have developed automatic programs known as CAPTCHA solvers to bypass the mechanism. With the presence of cheap labor in developing countries, hackers now have options to use human solvers. In this research, we develop a game theoretical framework to model the interactions between the defender and the attacker regarding the design and countermeasure of CAPTCHA system. With the result of equilibrium analysis, both parties can determine the optimal allocation of software-based or human-based CAPTCHA solvers. Counterintuitively, instead of the traditional wisdom of making CAPTCHA harder and harder, it may be of best interest of the defender to make CAPTCHA easier. We further suggest a welfare-improving CAPTCHA business model by involving decentralized cryptocurrency computation.
Duong, Tuyet, Chepurnoy, Alexander, Zhou, Hong-Sheng.  2018.  Multi-mode Cryptocurrency Systems. Proceedings of the 2Nd ACM Workshop on Blockchains, Cryptocurrencies, and Contracts. :35–46.

In the past years, the security of Bitcoin-like protocols has been intensively studied. However, previous investigations are mainly focused on the single-mode version of Bitcoin protocol, where the protocol is running among full nodes (miners). In this paper we initiate the study of multi-mode cryptocurrency protocols. We generalize the recent framework by Garay et al (Eurocrypt 2015) with new security de nitions that capture the security of realistic cryptocurrency systems. e.g. Bitcoin with full and lightweight nodes. As an immediate application of our new framework, we analyze the security of existing blockchain pruning proposals for Bitcoin and Ethereum aiming to improve the storage e ciency of network nodes by pruning unnecessary information from the ledger.