Michiel Van Beirendonck, Louis-Charles Trudeau, Pascal Giard, Alexios Balatsoukas‐Stimming
Lyra2REv2 is a hashing algorithm that consists of a chain of individual hashing algorithms and it is used as a proof-of-work function in several cryptocurrencies that aim to be ASIC-resistant. The most crucial hashing algorithm in the Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. In this work we present the first FPGA implementation of the aforementioned instance of Lyra2 and we explain how several properties of the algorithm can be exploited in order to optimize the design.
Blockchain as a new technology has created a great amount of hype and hope for different applications. There is a promise of a better, decentralised trust based on strict guarantees from cryptography. However, there is a great similarity in the structure of blockchains and classical iterated hash functions of the Merkle-Damgård (M-D) type. As the structure of M-D type hash functions has been extensively studied and many different structural weaknesses have been exposed, it is plausible to think that blockchains also share these structural problems. In this paper, we present the most relevant problems of M-D type hash functions and their relation to blockchains. We also examine how these might affect currently established blockchains. Our results can help in avoiding some problems in the design of new blockchain systems and also provide some (theoretical) limits on the trustworthiness of current blockchains.
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Mohammad Ahmad, Abdullah Al-Saleh, Fahad A. Al Masoud
Cryptocurrency subject attracted so many people for the last eight years around the globe. Satoshi’s Nakamoto’s, the founder of the bitcoin cryptocurrency behind this revolutionary change in digital money market. Bitcoin cryptocurrency uses “Power of Work” or simply PoW system as its mining algorithm. But in January of 2016, Ethereum cryptocurrency has launched which adopted a new system called “Power of Stake” or simply PoS that is used in Ethereum as its mining algorithm. This paper explores and compares PoW and PoS systems that is used widely today in cryptocurrencies digital money, concluding the pros and cons for each system with enabling to decide which one is more suitable and stable in digital money market.
Robert Alexandru Dobre, Radu Preda, Claudia Cristina Oprea, Ionuţ Pirnog
Image authentication importance increases as image acquisition becomes easier with the help of new technologies. Today, almost any phone has a camera with decent performances and sharing images is encouraged by social media. Image tampering is also decreasing in difficulty because of the advances in image editing software. Today's signature-based image authentication techniques rely on storing the image signature until the authentication is needed. This is a disadvantage because the storage support is usually unique, controlled by one entity and could fail. Also, this centralized approach is not fundamentally trustworthy. To solve these problems, the paper proposes a signature-based image authentication method resistant to JPEG compression which makes use of new blockchain technology to store the image signature. With this method, the signature is stored in a decentralized network, significantly increasing the security.
Advanced Steganography and Watermarking Techniques
Cryptocurrency wallets store the wallet's private key(s), and hence, are a lucrative target for attackers. With possession of the private key, an attacker virtually owns all of the currency in the compromised wallet. Managing cryptocurrency wallets offline, in isolated (`air-gapped') computers, has been suggested in order to secure the private keys from theft. Such air-gapped wallets are often referred to as `cold wallets.' In this paper we show how private keys can be exfiltrated from air-gapped wallets. In the adversarial attack model, the attacker infiltrates the offline wallet, infecting it with malicious code. The malware can be preinstalled or pushed in during the initial installation of the wallet, or it can infect the system when removable media (e.g., USB flash drive) is inserted into the wallet's computer in order to sign a transaction. These attack vectors have repeatedly been proven feasible in the last decade (e.g., [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]). Having obtained a foothold in the wallet, an attacker can utilize various air-gap covert channel techniques (bridgeware [11]) to jump the airgap and exfiltrate the wallet's private keys. We evaluate various exfiltration techniques, including physical, electromagnetic, electric, magnetic, acoustic, optical, and thermal techniques. This research shows that although cold wallets provide a high degree of isolation, it's not beyond the capability of motivated attackers to compromise such wallets and steal private keys from them. We demonstrate how a 256-bit private key (e.g., Bitcoin's private keys) can be exfiltrated from an offline, air-gapped wallet of a fictional character named Satoshi within a matter of seconds.
Open access
2 source records
cs.CR
Advanced Steganography and Watermarking Techniques
This paper intends to follow the evolution of the processing power needed to mine cryptocurrencies. Because by this year, 2018, they evolved to being over 1500 cryptos, we shell consider reviewing the first 5: Bitcoin, Ethereum, Ripple, Bitcoin Cash and Litecoin (a hierarchy given by coinmarketcap.com. We shall closely overview the first 2: Bitcoin (BTC) and Ethereum (ETH – Ether).
Darlene Godfrey-Welch, Remy Lagrois, Jared Law, Russell Scott Anderwald · 5 authors
Payment cards (e.g., credit and debit cards) are the most frequent form of payment in use today. A payment card transaction entails many verification information exchanges between the cardholder, merchant, issuing bank, a merchant bank, and third-party payment card processors. Today, a record of the payment transaction often records to multiple ledgers. Merchant’s incur fees for both accepting and processing payment cards. The payment card industry is in dire need of technology which removes the need for third-party verification and records transaction details to a single tamper-resistant digital ledger. The private blockchain is that technology. Private blockchain provides a linked list built with hash pointers used to record encrypted transactions in a structured manner. It is a decentralized and distributed and available to all participants involved in the transaction. Private blockchain removes the need for third-party validators, thereby reducing fees and increasing the Merchant’s overall transaction value.
Open access
Chaos-based Image/Signal Encryption
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
The ZK-STARK technology, published by Ben-Sasson et al. in ePrint 2018/046 is hailed by many as being a viable, efficient solution to the scaling problem of cryptocurrencies. In essence, a ZK-STARK proof uses a Merkle-tree to compress the data that needs to be verified, thus greatly reduces the communication overhead between the prover and the verifier. We propose MARVELlous a family of cryptographic algorithms specifically designed for STARK efficiency. The family currently includes the block cipher Jarvis and the hash function Friday. The design of Jarvis is inspired by the design of Rijndael, better known as the AES. By doing so we create a cipher with similar properties to those of Rijndael which allows us to reuse the wide-trail strategy to argue the resistance of the design against differential and linear cryptanalysis and focus our efforts on resistance against algebraic attacks. Friday is a Merkle-Damgard based hash function instantiated with Jarvis as its compression function thus it inherits its security properties up to the birthday bound. Jarvis and Friday have been suggested to be used in the Ethereum protocol by Ben-Sasson in Ethereum's Devcon IV. In this paper, we instantiate versions of Jarvis offering 128, 160, 192 and 256-bit security (both state- and key-size) which are used to implement Friday. We warmly invite the community to study and assess the security of the designs.
Since the seminal paper on Fully Homomorphic Encryption (FHE) by Gentry in 2009, a lot of work and improvements have been proposed, with an amazing number of possible applications. It allows outsourcing any kind of computations on encrypted data, and thus without leaking any information to the provider who performs the computations. This is quite useful for many sensitive data (finance, medical, etc.).
ECDSA is a standardized signing algorithm that is widely used in TLS, code signing, cryptocurrency and more. Due to its importance, the problem of securely computing ECDSA in a distributed manner (known as threshold signing) has received considerable interest. However, despite this interest, there is still no full threshold solution for more than 2 parties (meaning that any t -out-of- n parties can sign, security is preserved for any t-1 or fewer corrupted parties, and tłeq n can be any value thus supporting an honest minority) that has practical key distribution. This is due to the fact that all previous solutions for this utilize Paillier homomorphic encryption, and efficient distributed Paillier key generation for more than two parties is not known. In this paper, we present the first truly practical full threshold ECDSA signing protocol that has both fast signing and fast key distribution. This solves a years-old open problem, and opens the door to practical uses of threshold ECDSA signing that are in demand today. One of these applications is the construction of secure cryptocurrency wallets (where key shares are spread over multiple devices and so are hard to steal) and cryptocurrency custody solutions (where large sums of invested cryptocurrency are strongly protected by splitting the key between a bank/financial institution, the customer who owns the currency, and possibly a third-party trustee, in multiple shares at each). There is growing practical interest in such solutions, but prior to our work these could not be deployed today due to the need for distributed key generation.
Abstract We document numerous occurrences of pump-and-dump schemes (P&Ds) targeting cryptocurrencies, which tend to trigger short-term episodes that feature dramatic increases in prices, volume, and volatility, followed by quick reversals. The evidence we document, including price run-ups before P&Ds start, suggests wealth transfers from outsiders to insiders. Our findings based on wallet-level data are consistent with the reasoning that gambling preferences, overconfidence, and naïve reinforcement learning help explain P&D participation. Finally, exploiting two natural experiments in which exchanges altered P&D policies, we find evidence consistent with the idea that P&Ds contribute to reduced cryptocurrency liquidity and lower prices.
At present, the cloud storage used in searchable symmetric encryption schemes (SSE) is provided in a private way, which cannot be seen as a true cloud. Moreover, the cloud server is thought to be credible, because it always returns the search result to the user, even they are not correct. In order to really resist this malicious adversary and accelerate the usage of the data, it is necessary to store the data on a public chain, which can be seen as a decentralized system. As the increasing amount of the data, the search problem becomes more and more intractable, because there does not exist any effective solution at present. In this paper, we begin by pointing out the importance of storing the data in a public chain. We then innovatively construct a model of SSE using blockchain(SSE-using-BC) and give its security definition to ensure the privacy of the data and improve the search efficiency. According to the size of data, we consider two different cases and propose two corresponding schemes. Lastly, the security and performance analyses show that our scheme is feasible and secure.
Alexei Zamyatin, Katinka Wolter, Sam M. Werner, Peter G. Harrison · 6 authors
Cryptocurrency mining can be said to be the modern alchemy, involving as it does the transmutation of electricity into digital gold. The goal of mining is to guess the solution to a cryptographic puzzle, the difficulty of which is determined by the network, and thence to win the block reward and transaction fees. Because the return on solo mining has a very high variance, miners band together to create so-called mining pools. These aggregate the power of several individual miners, and, by distributing the accumulated rewards according to some scheme, ensure a more predictable return for participants.In this paper we formulate a model of the dynamics of a queue-based reward distribution scheme in a popular Ethereum mining pool and develop a corresponding simulation. We show that the underlying mechanism disadvantages miners with above-average hash rates. We then consider two-miner scenarios and show how large miners may perform attacks to increase their profits at the expense of other participants of the mining pool. The outcomes of our analysis show the queue-based reward scheme is vulnerable to manipulation in its current implementation.
Algebra is one of the important fields of mathematics. It concerns with the study and manipulation of mathematical symbols. It also concerns with the study of abstractions such as groups, rings, and fields. Due to the development of these abstractions, it is extended to consider other structures, such as vectors, matrices, and polynomials, which are non-numerical objects. Computer algebra is the implementation of algebraic methods as algorithms and computer programs. Recently, many algebraic cryptosystem protocols are based on non-commutative algebraic structures, such as authentication, key exchange, and encryption-decryption processes are adopted. Cryptography is the science that aimed at sending the information through public channels in such a way that only an authorized recipient can read it. Ring theory is the most attractive category of algebra in the area of cryptography. In this paper, we employ the algebraic structure called skew -Armendariz rings to design a neoteric algorithm for zero knowledge proof. The proposed protocol is established and illustrated through numerical example, and its soundness and completeness are proved.