Twenty Percent and a Few Days – Optimising a Bitcoin Majority Attack
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Bitcoin is a distributed online payment system that organises transactions into blocks. The size of blocks is limited to 1 megabyte, which also limits the number of transactions per second that can be confirmed. This year several attempts have been made to create a fork or a split that removes this restriction. One such alternative is Bitcoin Unlimited (BTU). Proponents of BTU have suggested to use a type of majority attack to force other Bitcoin miners to adopt BTU.
In this paper we model this attack in Uppaal, and analyse how long it will take for an attack to succeed, depending on the share the attacker has of the total network, and the so-called confirmation depth. The analysis shows that with a share of 20% an attack will be successful within a few days. This paper also looks at the effect of increasing the confirmation depth as a countermeasure.
- 1.Bitcoin charts (2017). https://blockchain.info/charts
- 3.Beukema, W.: Formalising the bitcoin protocol. In: 21th Twente Student Conference on IT (2014)Google Scholar
- 4.Bonneau, J., Miller, A., Clark, J., Narayanan, A., Kroll, J.A., Felten, E.W.: Research perspectives and challenges for bitcoin and cryptocurrencies. IACR Cryptology ePrint Archive 2015, 261 (2015)Google Scholar
- 5.Cawrey, D.: Are 51% Attacks a Real Threat to Bitcoin? CoinDesk, June 2014. https://www.coindesk.com/51-attacks-real-threat-Bitcoin/
- 6.Chaudhary, K., Fehnker, A., van de Pol, J., Stoelinga, M.: Modeling and verification of the bitcoin protocol. In: MARS 2015. EPTCS (2015)Google Scholar
- 7.David, A., Larsen, K.G., Legay, A., Mikučionis, M., Poulsen, D.B.: STTT. Uppaal SMC tutorial 17(4), 397–415 (2015)Google Scholar
- 8.Herrmann, M.: Implementation, evaluation and detection of a doublespend-attack on Bitcoin. Master’s thesis, Master Thesis ETH Zürich, April 2012Google Scholar
- 9.Nakamoto, S.: Bitcoin: A peer-to-peer electronic cash system (2009). http://www.Bitcoin.org
- 10.Shin, L.: What Will Happen At The Time Of The Bitcoin Hard Fork? Forbes, October 2017. https://www.forbes.com/sites/laurashin/2017/10/31/what-will-happen-at-the-time-of-the-bitcoin-hard-fork/
- 11.Van Wirdum, A.: Bitcoin Unlimited Miners May Be Preparing a 51% Attack on Bitcoin. Bitcoin Magazine, March 2017. https://Bitcoinmagazine.com/articles/Bitcoin-unlimited-miners-may-be-preparing-51-attack-Bitcoin/