@article {16778,
	title = {Partial Pre-Image Attack on Proof-of-Work based Blockchains},
	journal = {Blockchain: Research and Applications},
	year = {2024},
	abstract = {Blockchain (BC) is the type of distributed ledger technology that consists of a growing list of records, called blocks, that are securely linked together using cryptography. Each BC-based solution deploys a specific consensus algorithm that guarantees the consistency of the ledger over time. The most famous, and yet claimed to be the most secure, is the Proof-of-Work (PoW) consensus algorithm. In this paper,we revisit the fundamental calculations and assumptions of this algorithm, originally presented in the Bitcoin white paper. We break down its claimed calculations, in order to better understand the underlying assumptions of the proposal. We also propose a novel formalization model of the PoW mining problem using the Birthday paradox. We utilize this model to formalize and analyze Partial Pre-Image attacks on PoW-based BCs, with formal analysis that confirmed the experimental results and the previously proposed implications. We build on those analyses and propose new concepts for benchmarking the security of PoW-based systems, including Critical Difficulty and Critical Difficulty per given portion. Our calculations resulted in several important findings including the profitability of launching Partial Pre-Image attacks on PoW-based BCs, once the mining puzzle difficulty reaches a given threshold. Specifically, for any compromised portion of the network (q < 0.5; honest majority assumption still holds), the attack was formally proven profitable, once the PoW mining puzzle difficulty reaches 56 leading zeros.},
	keywords = {Blockchain, Hash functions, Partial pre-image attack, Proof-of-Work, Security},
	doi = {10.1016/j.bcra.2024.100194},
	url = {https://www.sciencedirect.com/science/article/pii/S2096720924000071},
	author = {Baniata, Hamza and Kert{\'e}sz, Attila}
}
@article {16781,
	title = {FoBSim: an extensible open-source simulation tool for integrated fog-blockchain systems},
	journal = {PeerJ Computer Science},
	volume = {vol 7},
	year = {2021},
	abstract = {A lot of hard work and years of research are still needed for developing successful Blockchain (BC) applications. Although it is not yet standardized, BC technology was proven as to be an enhancement factor for security, decentralization, and reliability, leading to be successfully implemented in cryptocurrency industries. Fog computing (FC) is one of the recently emerged paradigms that needs to be improved to serve Internet of Things (IoT) environments of the future. As hundreds of projects, ideas, and systems were proposed, one can find a great R\&D potential for integrating BC and FC technologies. Examples of organizations contributing to the R\&D of these two technologies, and their integration, include Linux, IBM, Google, Microsoft, and others. To validate an integrated Fog-Blockchain protocol or method implementation, before the deployment phase, a suitable and accurate simulation environment is needed. Such validation should save a great deal of costs and efforts on researchers and companies adopting this integration. Current available simulation environments facilitate Fog simulation, or BC simulation, but not both. In this paper, we introduce a Fog-Blockchain simulator, namely FoBSim, with the main goal to ease the experimentation and validation of integrated Fog-Blockchain approaches. According to our proposed workflow of simulation, we implement different Consensus Algorithms (CA), different deployment options of the BC in the FC architecture, and different functionalities of the BC in the simulation. Furthermore, technical details and algorithms on the simulated integration are provided. We validate FoBSim by describing the technologies used within FoBSim, highlighting FoBSim{\textquoteright}s novelty compared to the state-of-the-art, discussing the event validity in FoBSim, and providing a clear walk-through validation. Finally, we simulate case studies, then present and analyze the obtained results, where deploying the BC network in the fog layer shows enhanced efficiency in terms of total run time and total storage cost.},
	keywords = {Blockchain, fog computing, simulation},
	doi = {10.7717/peerj-cs.431},
	url = {https://peerj.com/articles/cs-431/},
	author = {Baniata, Hamza and Kert{\'e}sz, Attila}
}
