Blockchain Papers

Dmitry Efanov, Pavel Roschin

Conceptually, the blockchain is a distributed database containing records of transactions that are shared among participating members. Each transaction is confirmed by the consensus of a majority of the members, making fraudulent transactions unable to pass collective confirmation. Once a record is created and accepted by the blockchain, it can never be altered or disappear. Nowadays the blockchain technology is considered as the most significant invention after the Internet. If the latter connects people to realize on-line business processes, the former could decide the trust problem by peer-to-peer networking and public-key cryptography. The purpose of this paper is to consider on distinct use cases at the all-pervasive impact of the blockchain technology and look at this as an inalienable part of our daily life.

Qi Wang, Xiangxue Li, Yu Yu

Bitcoin is promoted as decentralized cryptocurrency by using pseudonym to achieve anonymity. Unfortunately, numerous seminal works have demonstrated that Bitcoin only offers weak anonymity in practice. Indeed, the practical technologies of clustering and flow analysis are much effective for tracing Bitcoin transaction and thereby revealing the owner involved. Otherwise said, user's privacy in Bitcoin has been sadly degenerated to be linkable. In this paper, we propose a completely decentralized scheme that can provide full anonymity in Bitcoin. The idea behind the output is to exploit a secure escrow address, which is consensual by all the involved users. The escrow address is generated from the trick of cryptographically secure distributed key generation and can then be used for mixing transactions in Bitcoin. Our protocol is secure against malicious adversaries. The users can jointly perform the protocol and successfully accomplish the transaction without the help of any (trusted) third party and no extra fees. Besides, our proposal is completely compatible with the current Bitcoin architecture.

Cécile Pierrot, Benjamin Wesolowski

No abstract is available for this record.

Daniel Augot, Hervé Chabanne, Olivier Clémot, William R. George

The most fundamental purpose of blockchain technology is to enable\npersistent, consistent, distributed storage of information. Increasingly common\nare authentication systems that leverage this property to allow users to carry\ntheir personal data on a device while a hash of this data is signed by a\ntrusted authority and then put on a blockchain to be compared against. For\ninstance, in 2015, MIT introduced a schema for the publication of their\nacademic certificates based on this principle. In this work, we propose a way\nfor users to obtain assured identities based on face-to-face proofing that can\nthen be validated against a record on a blockchain. Moreover, in order to\nprovide anonymity, instead of storing a hash, we make use of a scheme of Brands\nto store a commitment against which one can perform zero-knowledge proofs of\nidentity. We also enforce the confidentiality of the underlying data by letting\nusers control a secret of their own. We show how our schema can be implemented\non Bitcoin's blockchain and how to save bandwidth by grouping commitments using\nMerkle trees to minimize the number of Bitcoin transactions that need to be\nsent. Finally, we describe a system in which users can gain access to services\nthanks to the identity records of our proposal.\n

Mehrdad Salimitari, Mainak Chatterjee, Murat Yüksel, Eduardo L. Pasiliao

It is predicted that cryptocurrencies will play an important role in the global economy. Therefore, it is prudent for us to understand the importance and monetary value of such cryptocurrencies, and strategize our investments accordingly. One of the ways to obtain cryptocurrency is via mining. As solo mining is not possible because of the computational requirements, pool mining has gained popularity. In this paper, we focus on Bitcoin and its pools. With more than 20 pools in the network of Bitcoin and other cryptocurrencies, it becomes challenging for a new miner to decide the pool he must join such that the profit is maximized. We use prospect theory to predict the profit that a specific miner, given his hash rate power and electricity costs, is expected to make from each pool. A utility value is calculated for each pool based on its recent performance, hash rate power, total number of the pool members, reward distribution policy of the pool, electricity fee in the new miner's region, pool fee, and the current Bitcoin value. Then, based on these parameters during a certain time duration, the most profitable pool is found for that miner. We show how the utility values from a pool varies with electricity fee and dollar equivalent of a Bitcoin. To find the accuracy of our predictions, we mine Bitcoin by joining 5 different pools- AntPool, F2Pool, BTC.com, Slushl'ool, and BatPool. Using an Antminer 55 for each pool, we mine Bitcoin for 40 consecutive days. Results reveal that our prospect theoretic predictions are consistent with what we actually mine; however predictions using expected utility theory are not as close.

Diego Romano, Giovanni Schmid

After more than eight years since the launch of Bitcoin, the decentralized transaction ledger functionality implemented through the blockchain technology is being used not only for cryptocurrencies, but to register, confirm and transfer any kind of contract and property. In this work, we analyze the most relevant functionalities and known issues of this technology, with the intent of pointing out the possible behaviours that are not as efficient and reliable as they should be when thinking with a broader outlook.

Xiaoqi Li, Peng Jiang, Ting Chen, Xiapu Luo · 5 authors

Since its inception, the blockchain technology has shown promising application prospects. From the initial cryptocurrency to the current smart contract, blockchain has been applied to many fields. Although there are some studies on the security and privacy issues of blockchain, there lacks a systematic examination on the security of blockchain systems. In this paper, we conduct a systematic study on the security threats to blockchain and survey the corresponding real attacks by examining popular blockchain systems. We also review the security enhancement solutions for blockchain, which could be used in the development of various blockchain systems, and suggest some future directions to stir research efforts into this area.

Anand Kumar Mishra, Shrikant Tiwari, Kanchan Naithani, Amit Kumar Tyagi

Blockchain has drawn attention as the next-generation financial technology due to its security that suits the informatization era. In particular, it provides security through the authentication of peers that share virtual cash, encryption, and the generation of hash value. According to the global financial industry, the market for security-based blockchain technology is expected to grow to about USD 20 billion by 2020. In addition, blockchain can be applied beyond the Internet of Things (IoT) environment; its applications are expected to expand. Cloud computing has been dramatically adopted in all IT environments for its efficiency and availability. In this paper, we discuss the concept of blockchain technology and its hot research trends. In addition, we will study how to adapt blockchain security to cloud computing and its secure solutions in detail.

Deepayan Bhowmik, Feng Tian

A distributed and tamper proof media transaction framework is proposed based on the blockchain model. Current multimedia distribution does not preserve self-retrievable information of transaction trails or content modification histories. For example, digital copies of valuable artworks, creative media and entertainment contents are distributed for various purposes including exhibitions, gallery collections or in media production workflow. Original media is often edited for creative content preparation or tampered with to fabricate false propaganda over social media. However there is no existing trusted mechanism that can easily retrieve either the transaction trails or the modification histories. We propose a novel watermarking based Multimedia Blockchain framework that can address such issues. The unique watermark information contains two pieces of information: a) a cryptographic hash that contains transaction histories (blockchain transactions log) and b) an image hash that preserves retrievable original media content. Once the watermark is extracted, first part of the watermark is passed to a distributed ledger to retrieve the historical transaction trail and the latter part is used to identify the edited / tampered regions. The paper outlines the requirements, the challenges and demonstrates the proof of this concept.

Daniel Augot, Hervé Chabanne, Olivier Clémot, William R. George

The most fundamental purpose of blockchain technology is to enable persistent, consistent, distributed storage of information. Increasingly common are authentication systems that leverage this property to allow users to carry their personal data on a device while a hash of this data is signed by a trusted authority and then put on a blockchain to be compared against. For instance, in 2015, MIT introduced a schema for the publication of their academic certificates based on this principle. In this work, we propose a way for users to obtain assured identities based on face-to-face proofing that can then be validated against a record on a blockchain. Moreover, in order to provide anonymity, instead of storing a hash, we make use of a scheme of Brands to store a commitment against which one can perform zero-knowledge proofs of identity. We also enforce the confidentiality of the underlying data by letting users control a secret of their own. We show how our schema can be implemented on Bitcoin's blockchain and how to save bandwidth by grouping commitments using Merkle trees to minimize the number of Bitcoin transactions that need to be sent. Finally, we describe a system in which users can gain access to services thanks to the identity records of our proposal.

Mauro Conti, E. Sandeep Kumar, Chhagan Lal, Sushmita Ruj

Bitcoin is a popular cryptocurrency that records all transactions in a distributed append-only public ledger called blockchain. The security of Bitcoin heavily relies on the incentive-compatible proof-of-work (PoW) based distributed consensus protocol, which is run by the network nodes called miners. In exchange for the incentive, the miners are expected to maintain the blockchain honestly. Since its launch in 2009, Bitcoin economy has grown at an enormous rate, and it is now worth about 150 billions of dollars. This exponential growth in the market value of bitcoins motivate adversaries to exploit weaknesses for profit, and researchers to discover new vulnerabilities in the system, propose countermeasures, and predict upcoming trends. In this paper, we present a systematic survey that covers the security and privacy aspects of Bitcoin. We start by giving an overview of the Bitcoin system and its major components along with their functionality and interactions within the system. We review the existing vulnerabilities in Bitcoin and its major underlying technologies such as blockchain and PoW-based consensus protocol. These vulnerabilities lead to the execution of various security threats to the standard functionality of Bitcoin. We then investigate the feasibility and robustness of the state-of-the-art security solutions. Additionally, we discuss the current anonymity considerations in Bitcoin and the privacy-related threats to Bitcoin users along with the analysis of the existing privacy-preserving solutions. Finally, we summarize the critical open challenges, and we suggest directions for future research towards provisioning stringent security and privacy solutions for Bitcoin.

Zibin Zheng, Shaoan Xie, Hong‐Ning Dai, Xiangping Chen · 5 authors

Blockchain, which is the backbone of Bitcoin, has recently received a lot of attention. Blockchain functions as an immutable ledger that enables decentralized transactions. Numerous fields, such as the Internet of Things (IoT), reputation systems, and financial services, are being covered by blockchain-based applications. However, blockchain technology still faces numerous difficulties, such as scalability and security issues, that need to be resolved. A comprehensive overview of blockchain technology is provided in this paper. First, we compare some common consensus algorithms utilized by various blockchains and provide an overview of the architecture of blockchains. In addition, a brief list of recent advancements and technical difficulties is provided. In addition, we outline potential blockchain trends for the future.

Ahmed Ben Ayed

Blockchain is offering new opportunities to develop new types of digital services. While research on the topic is still emerging, it has mostly focused on the technical and legal issues instead of taking advantage of this novel concept and creating advanced digital services. In this paper, we are going to leverage the open source Blockchain technology to propose a design for a new electronic voting system that could be used in local or national elections. The Blockchain-based system will be secure, reliable, and anonymous, and will help increase the number of voters as well as the trust of people in their governments.

Sean Rowan, Michael Clear, Mário Gerla, Meriel Huggard · 5 authors

Autonomous and self-driving vehicles are appearing on the public highways.\nThese vehicles commonly use wireless communication techniques for both\nvehicle-to-vehicle and vehicle-to-infrastructure communications. Manufacturers,\nregulators and the public are understandably concerned about large-scale\nsystems failure or malicious attack via these wireless vehicular networks. This\npaper explores the use of sensing and signalling devices that are commonly\nintegrated into modern vehicles for side-channel communication purposes.\nVisible light (using a CMOS camera) and acoustic (ultrasonic audio)\nside-channel encoding techniques are proposed, developed and evaluated in this\ncontext. The side-channels are examined both theoretically and experimentally\nand an upper bound on the line code modulation rate that is achievable with\nthese side channel schemes in the vehicular networking context is established.\nA novel inter-vehicle session key establishment protocol, leveraging both\nside-channels and a blockchain public key infrastructure, is then presented. In\nlight of the limited channel capacity and the interoperability/security\nrequirements for vehicular communications, techniques for constraining the\nthroughput requirement, providing device independence and validating the\nlocation of the intended recipient vehicle, are presented. These reduce the\nnecessary device handshake throughput to 176 bits for creating symmetric\nencryption and message authentication keys and in verifying a vehicle's\ncertificate with a recognised certification authority.\n

Giuseppe Pappalardo, Tiziana Di Matteo, Guido Caldarelli, Tomaso Aste

We investigate Bitcoin network observing transactions broadcasted into the network during a week from 04/05/2016 and then monitoring their inclusion into the blockchain during the following seven months.We unveil that 42% of the transactions are still not included in the Blockchain after 1 h from their appearance and 20% of the transactions are still not included in the Blockchain after 30 days, therefore revealing a great inefficiency in the Bitcoin system. However, we observe that most of these “forgotten” transactions have low values and in terms of transferred value the system is less inefficient with 93% of the transactions value being included into the Blockchain within 3 h and 98.8% within a day. The fact that a sizeable fraction of transactions is not processed timely casts serious doubts on the usability of the Bitcoin Blockchain for reliable time-stamping purposes. It also calls for a debate about the right systems of incentives which a peer-to-peer unintermediated system should introduce to promote efficient transaction recording

S. Matthew English, Ehsan Nezhadian

Heretofore the concept of "blockchain" has not been precisely defined. Accordingly the potential useful applications of this technology have been largely inflated. This work sidesteps the question of what constitutes a blockchain as such and focuses on the architectural components of the Bitcoin cryptocurrency, insofar as possible, in isolation. We consider common problems inherent in the design of effective supply chain management systems. With each identified problem we propose a solution that utilizes one or more component aspects of Bitcoin. This culminates in five design principles for increased efficiency in supply chain management systems through the application of incentive mechanisms and data structures native to the Bitcoin cryptocurrency protocol.

Malik Khurram Awan, Agostino Cortesi

No abstract is available for this record.

Paolo Tasca, Thayabaran Thanabalasingham

No abstract is available for this record.

Saurav Chakraborty, Kaushik Dutta, Don Berndt

No abstract is available for this record.

Rishab Goyal, Vipul Goyal

Blockchain technology has the potential to disrupt how cryptography is done. In this work, we propose to view blockchains as an “enabler”, much like indistinguishability obfuscation [5, 23, 46] or one-way functions, for building a variety of cryptographic systems. Our contributions in this work are as follows: 1. A Framework for Proof-of-Stake based Blockchains: We provide an abstract framework for formally analyzing and defining useful security properties for Proof-of-Stake (POS) based blockchain protocols. Interestingly, for some of our applications, POS based protocols are more suitable. We believe our framework and assumptions would be useful in building applications on top of POS based blockchain protocols even in the future. 2. Blockchains as an Alternative to Trusted Setup Assumptions in Cryptography: A trusted setup, such as a common reference string (CRS) has been used to realize numerous systems in cryptography. The paragon example of a primitive requiring trusted setup is a non-interactive zero-knowledge (NIZK) system. We show that already existing blockchains systems including Bitcoin, Ethereum etc. can be used as a foundation (instead of a CRS) to realize NIZK systems. The novel aspect of our work is that it allows for utilizing an already existing (and widely trusted) setup rather than proposing a new one. Our construction does not require any additional functionality from the miners over the already existing ones, nor do we need to modify the underlying blockchain protocol. If an adversary can violate the security of our NIZK, it could potentially also take over billions of dollars worth of coins in the Bitcoin, Ethereum or any such cryptocurrency! We believe that such a “trusted setup” represents significant progress over using CRS published by a central trusted party. Indeed, NIZKs could further serve as a foundation for a variety of other cryptographic applications such as round efficient secure computation [33, 36]. 3. One-time programs and pay-per use programs: Goldwasser et al. [29] introduced the notion of one time program and presented a construction using tamper-proof hardware. As noted by Goldwasser et al. [29], clearly a one-time program cannot be solely software based, as software can always be copied and run again. While there have been a number of follow up works [4, 6, 30], there are indeed no known constructions of one-time programs which do not rely on self destructing tamper-proof hardware (even if one uses trusted setup or random oracles). Somewhat surprisingly, we show that it is possible to base one-time programs on POS based blockchain systems without relying on trusted hardware. Our ideas do not seem to translate over to Proof-of-Work (POW) based blockchains. We also introduce the notion of pay-per-use programs which is simply a contract between two parties — service provider and customer. A service provider supplies a program such that if the customer transfers a specific amount of coins to the provider, it can evaluate the program on any input of its choice once, even if the provider is offline. This is naturally useful in a subscription based model where your payment is based on your usage.

Nicolas T. Courtois, Rebekah Mercer

Bitcoin is an open source payment system with a market capitalization of about 15 G$. During the years several key management solutions have been proposed to enhance bitcoin. The common characteristic of these techniques is that they allow to derive public keys independently of the private keys, and that these keys match. In this paper we overview the historical development of such techniques, specify and compare all major variants proposed or used in practical systems. We show that such techniques can be designed based on 2 distinct ECC arithmetic properties and how to combine both. A major trend in blockchain systems is to use by Stealth Address (SA) techniques to make different payments made to the same payee unlikable. We review all known SA techniques and show that early variants are less secure. Finally we propose a new SA method which is more robust against leakage and against various attacks.

Peter Mell, John Kelsey, James M. Shook

Most modern electronic devices can produce a random number. However, it is difficult to see how a group of mutually distrusting entities can have confidence in any such hardware-produced stream of random numbers, since the producer could control the output to their gain. In this work, we use public and immutable cryptocurrency smart contracts, along with a set of potentially malicious randomness providers, to produce a trustworthy stream of timestamped public random numbers. Our contract eliminates the ability of a producer to predict or control the generated random numbers, including the stored history of random numbers. We consider and mitigate the threat of collusion between the randomness providers and miners in a second, more complex contract.

L Er-Rajy, El Kiram My A, El Ghazouani M, Omar Achbarou

Bitcoin has experienced rapid growth in the transactions number and in their value since its appearance in 2008. Its success is mainly due to the innovative use of a peer-to-peer network to implement all aspects of the currency life cycle, from creation to transfer between users. Bitcoin offers cash transactions that are almost instant and non-refundable, while allowing truly global transactions processed at the same speed as local ones. It offers a public transactions history, which allows untrusted audibility, and introduces many new and innovative use cases such as smart property, micropayments, contracts and escrow transactions for disputes mediation. However, the same features that make Bitcoin attractive to its end users are also its main limitations. Its decentralized nature limits the number of transactions and the speed at which transactions can be carried out and confirmed. The problem with slow confirmations is combined with the semantics of the confirmations which are not definitive, requiring several confirmations and further delaying the transaction acceptance. In this paper, we described the operating principles of peer-to-peer cryptographic currencies and especially security of bitcoin system. Moreover, For Bitcoin enhancements and additional mitigations we provide ideas for node auditing users in the network in aim to keep clients from the trusted transaction branch database generated by the attackers.

Daniel Augot, Hervé Chabanne, Thomas Chenevier, William R. George · 5 authors

We present an identity management scheme built into the Bitcoin blockchain, allowing for identities that are as indelible as the blockchain itself. Moreover, we take advantage of Bitcoin's decentralized nature to facilitate a shared control between users and identity providers, allowing users to directly manage their own identities, fluidly coordinating identities from different providers, even as identity providers can revoke identities and impose controls.