Authors:
Nicolas T. Courtois
1
;
Pinar Emirdag
2
and
Zhouyixing Wang
1
Affiliations:
1
University College London, United Kingdom
;
2
Independent Market Structure Professional, United Kingdom
Keyword(s):
e-Payment, Crypto Currencies, Bitcoin, Double-spending attacks, Hash Functions, Man-In-the-Middle Attacks, Stratum Protocol.
Related
Ontology
Subjects/Areas/Topics:
Communication and Software Technologies and Architectures
;
Computer-Supported Education
;
Data Engineering
;
Data Integrity
;
Databases and Data Security
;
e-Business
;
Energy and Economy
;
Enterprise Information Systems
;
Information and Systems Security
;
Information Technologies Supporting Learning
;
Mobile and Pervasive Computing
;
Security and Privacy
;
Sustainable Computing and Communications
;
Telecommunications
Abstract:
In this paper we study the question of centralisation in bitcoin digital currency. In theory bitcoin has been designed to be a totally decentralized distributed system. Satoshi Nakamoto has very
clearly postulated that each node should be collecting recent transactions and trying to create new blocks [Satoshi08]. In bitcoin transactions are aggregated in block in order to authenticate
them and form an official ledger and history of bitcoin transactions. In practice as soon as expensive ASIC bitcoin miners have replaced general-purpose hardware, production of bitcoins and the
validation of transactions has concentrated in the hands of a smaller group of people. Then at some moment in early 2012 an important decision was taken: the Stratum protocol was designed
[Palatinus12] which took a deliberate decision to move the power of selecting which transactions are included in blocks from miners to pool managers. The growing difficulty of mining and large
standard deviation in this proces
s [Rosenfeld13, CourtoisBahack14] made that majority of miners naturally shifted to pooled mining. At this moment bitcoin ceased being a decentralized democratic system.
In this paper we survey the question of a 51% attacks and show that there is a large variety of plausible attack scenarios. In particular we study one particularly subversive
attack scenario which depends on non-trivial internal details of the bitcoin hashing process. How does it compare with the current mining practices? We have study the Stratum protocol in four
popular real-life mining con figurations. Our analysis shows that pools could very easily cheat the majority of people. However the most subversive versions of the attack are NOT facilitated and
could potentially be detected.
(More)