Home > Vol 1 (2016) > Rizun Subchains: A Technique to Scale Bitcoin and Improve the User Experience Abstract Keywords Full Text: PDF Open Review References Andresen, G.“[/pipermail/bitcoin-dev/2015-September/011157.html /index.php?topic=673415.msg7658481#msg7658481 Barski, C., and Wilmer, C. Bitcoin for the Befuddled.San Francisco: No Starch Press (2014) BitFury Group.“/content/4-white-papers-research/bitfury- incentive_mechanisms_for_securing_the_bitcoin_blockchain-1.pdf BitFury Group.“/content/4-white-papers-research/pos-vs-pow-1.0.2.pdf Carlsten, M., Kalodner, H., Narayanan, A.“Mind the Gap: Security Implications of the Evolution of Bitcoin Mining.” Scaling Bitcoin Montreal (12 September 2015) Carlsten, M., Kalodner, H., Weinberg, S. M., Narayanan, A.“On the Instability of Bitcoin Without the Block Reward.” ACM CCS 2016. http://randomwalker.info/publications/mining_CCS.pdf Clifford, A., Rizun, P. R., Suisani, A., Stone, G. A., Tschipper, P.

“Towards Massic On-chain Scaling: Block Propagation Results With Xthin.Part 3 of 5: Xthin blocks are less affected by the Great Firewall of China than standard blocks.” Medium (4 Jun 2016)./@peter_r/towards-massive-on- chain-scaling-block-propagation-results-with-xthin-792a752c14c2 Clifford, A., Rizun, P. R., Suisani, A., Stone, G. A., Tschipper, P.Part 5 of 5: Massive on-chain scaling begins with block sizes up to 20 MB.” Medium (13 Jun 2016)./@peter_r/towards-massive-on-chain-scaling-block- propagation-results-with-xthin-5145c9648426 Croman, K., et al.epay bitcoin wallet“On Scaling Decentralized Blockchains.” Financial Cryptography and Data Security http://fc16.ifca.ai/bitcoin/papers/CDE+16.pdf Decker C., Wattenhofer R.bitcointalk etoken“Information Propagation in the Bitcoin Network.” 13th IEEE International Conference on Peer-to-Peer Computing, Trento, Italy, September 2013 Eyal, I., Gencer, A. E., Sirer, E. G., van Renesse, R.bitcoin faucet bot 2017

“Bitcoin-NG: A Scalable Blockchain Protocol.” arXiv (7 October 2015).“The Bitcoin Mining Game.” SSRN (11 March 2014).“Brading the Blockchain.” Presentation at Scaling Bitcoin Hong Kong (7 December 2015)./hongkong2015/presentations/DAY2/2_breaking_the_chain_1_mcelrath.pdf /toposign/chip_and_pin_is_broken.pdf No Author.“Bitcoin Network Capacity Analysis – Part 6: Data Propagation.” Tradeblock Blog (23 June 2015) /blog/bitcoin-network-capacity-analysis-part-6-data-propagation No Author.“Law of supply.” Wikipedia.“Median Transaction Confirmation Time (With Fee Only)” chart.Blockchain.info (13 December 2015) https://blockchain.info/charts/avg-confirmation-time No Author.“Scalability.” Bitcoin Wiki (13 December 2015) https://en.bitcoin.it/wiki/Scalability No Author.“Total Number of Transactions” chart.Blockchain.info (13 December 2015) https://blockchain.info/charts/n-transactions-total Pinna, D.“/doc/276849939/On-the-Nature-of-Miner-Advantages-in-Uncapped-Block- Size-Fee-Markets Pseudonymous (“awemany”).

Comment in “Block Space as a Commodity.” Bitcoin Forum (26 September 2015) https://bitco.in/forum/threads/block-space-as-a-commodity-a-transaction-fee-market-exists-without-a- block-size-limit.58/page-4#post-1409 Pseudonymous (“rocks”).Comment in “Gold Collapsing.Bitcoin UP.” Bitcoin Forum.(12 November 2015) https://bitco.in/forum/threads/gold-collapsing-bitcoin-up.16/page-99#post-3585 Pseudonymous (“TierNolan”).“A Transaction Fee Market Exists Without a Block Size Limit.” No Publisher (2015) https://www.bitcoinunlimited.info/resources/feemarket.pdf Rizun, P.“/r/btc/comments/4t6guk/the_marginal_cost_of_adding_another_transaction/ Rosenbaum, K., Russell, R.“IBLT and Weak Block Propagation Performance.” Scaling Bitcoin Hong Kong (6 December 2015) Stone, G.“An Examination of Bitcoin Network Throughput Via Analysis of Single Transaction Blocks.” No Publisher (2015) http://www.bitcoinunlimited.info/1txn Todd, P.“Block Publication Incentives for Miners.” No Publisher (29 June 2016).

/2016/block-publication-incentives-for-miners Tschipper, P., “BUIP010: Xtreme Thinblocks.” Bitcoin Forum (1 January 2016).https://bitco.in/forum/threads/buip010-passed-xtreme-thinblocks.774/ /10.5195/ledger.2016.40 Refbacks There are currently no refbacks.Copyright (c) 2016 Peter R. Rizun This work is licensed under a Creative Commons Attribution 4.0 International License.I am a first year PhD student in the Department of Computer Science at Princeton University and a Graduate Student Fellow at the Center for Information Technology Policy (CITP).My adviser is Arvind Narayanan.I am broadly interested in the security and anonymity of cryptographic currencies.Previously, I was a research assistant in the Information Security Research Group of Rainer Böhme and completed my bachelor and master studies in Information Systems at the University of Münster in Germany.During that time, I received fellowships from the German Academic Scholarship Foundation (Studienstiftung) and the German Academic Exchange Service (DAAD).

You can find me on Twitter, GitHub and VSCO.The bitcoin digital currency could be hijacked by “selfish miners” causing honest users to lose time, effort and money.Due to the way the anonymous, decentralised, peer-to-peer digital currency is produced through complex computational processes, a rogue group of “selfish miners” could hijack the currency and overwrite the shared record of transactions.That would wipe out the bitcoins belonging to honest users and possibly cause a collapse in the currency, say two researchers from Cornell University.The conditions for that to happen already exist.Ittay Eyal and Emin Gun Sirer, of the computing science department at Cornell University, New York, have worked out that the selfish mining group would need more than a 33% share of the computational power currently being used for generating bitcoins.Certain groups regularly break 25% of the global collective bitcoin mining power, and some already exceed the 33% share, the duo say.“The bitcoin ecosystem is open to manipulation, and potential takeover, by miners seeking to maximise their rewards,” Eyal and Gun Sirer say in a recently published paper on the Arxiv site.

“The protocol will never be safe against attacks by a selfish mining pool that commands more than 33% of the total mining power of the network.” While most users buy bitcoins from currency exchanges such as Mt Gox, some users produce new ones by “mining”, a process that requires computers to perform the calculations needed to make the digital currency work.Mining is time-consuming and expensive due to the way the currency is designed.Each bitcoin is more cryptographically complex than the previous one, requiring more computational time to "mine" it, and thus investment in electricity and use of computer hardware.Once the cryptographic calculation is complete for each bitcoin, a record of that bitcoin is written to a collectively shared ledger called the “blockchain”, which confirms that each bitcoin actually has value and has been correctly mined.Due to the peer-to-peer nature, only the latest or longest blockchain is recognised as valid - and it is this which poses a security risk, according to the researchers.

Most mining takes place in the open, with each newly produced bitcoin logged immediately in the public record.However, a “selfish” mining group operates by pooling computing resources, writing its newly calculated bitcoins to a private blockchain.Once that private blockchain is released, if it is longer than the publicly available blockchains currently in circulation it will overwrite them, destroying the value of the work done by others in preference to their own mined bitcoins.“The key insight behind the selfish mining strategy is to force the honest miners into performing wasted computations on the stale public branch.Specifically, selfish mining forces the honest miners to spend their cycles on blocks that are destined to not be part of the blockchain,” wrote the researchers.In effect, the rogue selfish mining group could claim more bitcoins for themselves, hijacking the currency.To do that, “higher revenues can lead new rational miners to join selfish miner pools, leading to a collapse of the decentralised currency,” warned the researchers, who proposed a solution that involves mining to random blockchains to eliminate the risk of selfish build up.