Not So Anonymous - Deanonymization of Blockchain Users
- 1. Not so Anonymous - Deanonymization of Blockchain Users Johannes Ahlmann CorkSec Meetup 2019-03-12 https://www.dailydot.com/news/anonymous-opfullerton-kelly-thomas/
- 2. Agenda • Is Bitcoin anonymous? • What is Deanonymization? • Why should I care? • What can I do about it? • Where to get cryptos? • Alternatives
- 3. About Me • Johannes Ahlmann • sensatus.io • On-Prem AI Models • Gathering and Enriching Web Data • Sales & Client Intelligence • webdata.org • Share Libraries and Best Practices • Bring Data Scientists and SME Companies together • ForDevelopers • AwesomeAvailableDatasets • Contact: johannes@sensatus.io sensatus.io
- 4. Pseudonyms • 1F1tAaz5x1HUXrCNLbtMDqcw6o5GNn4xqX • secret@protonmail.com • @johannes_cork • reddit_user • slashdot_user • ahljoh • 083 1762676 • Dread Pirate Roberts
- 5. Anonymity & Privacy Anonymity "without a name" Noone knows who you are Privacy Noone knows what you purchased and for what amount https://d262ilb51hltx0.cloudfront.net/max/1610/1*d0KdwdeKDi5m8n-sZdr-_A.png
- 6. Anonymity 1/2 • Pseudonymity - People are aware of one or multiple pseudonyms of yours, but not your true identity • Anonymity = Pseudonymity + Unlinkability • Unlinkability • Different actions of the same user should not be linkable to each other • Linking of addresses to users • Linking of transactions to users • Linking of senders to recipients
- 7. Anonymity 2/2 • Privacy vs. Decentralization • Public Ledger is core component in consensus and sharing state of the world • Bitcoin is pseudonymous, not anonymous • public addresses = pseudonyms • much less privacy than cash • Many Bitcoins are acquired through Exchanges or Mining Pools • Relatively few merchants/ market participants to trade with (retroactive geolocation) • Deanonymizing TOR using Bitcoin ;) • Fungibility
- 8. What is Deanonymization • Linking you to your addresses • Linking you to your transactions • Tagging, clustering of totality of addresses, transactions • Approaches • Transaction Graph Analysis • Realtime Network Analysis of P2P network
- 11. source: https://www.technologyreview.com/s/608716/bitcoin-transactions-arent-as-anonymous-as-everyone-hoped/ • 130 major merchants accepting Bitcoin • 53/ 130 leak payment information with > 40 total parties • Known fiat amount, timestamp • Unique linkage possible for 60% of (these specific) cases
- 12. Transaction Graph Analysis 1/2 Change Address Combined Addresses
- 13. Transaction Graph Analysis 2/2 • Bitcoin transactions are public • Active collection • Mining pools • Online wallets • Exchanges • Merchants • Gambling • Tagging clusters • One tagged address in cluster tags all cluster • Bitcoin address should only be used once An Analysis of Anonymity in the Bitcoin System F. Reid and M. Harrigan, PASSAT 2011
- 14. Realtime Network Analysis • "Attack" on the P2P Network • Peers distinguished over set of its (8) entry nodes • Linking inputs • Tagging clusters
- 16. Realtime Network Analysis • Linking of different transactions to same user • Each peer is trying to connect to 8 entry nodes • Network discovery • Servers • Receive incoming connections • Max. 117 incoming connections • Clients • 8 outgoing connections • Peers are distinguished over set of it’s entry nodes!
- 17. Remediation • Deterministic Address Pool Wallets • Random Address Pool Wallets • Tor • Mixers • Who can we trust? • Coinjoin • How to find Peers? • Anonymous cryptocurrencies
- 18. Anonymous Currencies Monero - Ring signatures Dash - Fork of bitcoin, coin-mixing service Zcash - zk-SNARK, zero knowledge proofs Verge - Tor and I2P network for privacy Komodo - Fork of Zcash, zk-SNARK Pivx - Fork of Dash, Zerocoin protocol (Legitimate goods vs. legitimate worries; how can this be used for good or bad?)
- 19. Thank You!
- 20. Resources • https://coincenter.org/entry/how-anonymous-is-bitcoin • https://bitcoinmagazine.com/articles/is-bitcoin-anonymous-a-complete-beginner-s-guide-1447875283/ • https://www.coursera.org/lecture/cryptocurrency/how-to-de-anonymize-bitcoin-qnS76 • https://www.slideshare.net/bhaslhofer/bitcoin-deanonymization-and-money-laundering-detection-strategies • https://pwlconf.org/2018/giulia-fanti/ • https://www.technologyreview.com/s/608716/bitcoin-transactions-arent-as-anonymous-as-everyone-hoped/ • https://decentralize.today/a-new-attack-vector-to-deanonymize-bitcoin-users-9c6dc433d4b6 • https://www.deepdotweb.com/2017/04/20/how-companies-are-deanonymizing-bitcoin/ • https://bitcoinsandblockchains.blogspot.com/2016/05/bitcoin-deanonymization.html • https://btcmanager.com/u-s-department-of-homeland-security-create-bitcoin-deanonymization-tool/ • https://www.deepdotweb.com/2018/01/02/using-bitcoin-transaction-analysis-deanonymizing-users-tor-hidden-services/ • https://www.researchgate.net/publication/305423583_Listening_to_Whispers_of_Ripple_Linking_Wallets_and_Deanony mizing_Transactions_in_the_Ripple_Network/download • https://www.youtube.com/embed/glyQy_e5LmM?