Wasabi Research Club #10 - CoinJoin Sudoku
Channel: Wasabi Wallet
Date: 10/03/2020

In today's episode we introduce the topic of examining the weaknesses in the privacy guarantees of CoinJoin. Wediscuss the concept of shared coin, fingerprinting, breaking down transactions, and the limitations of using CoinJoin to prevent analysis. We also discuss the privacy implications of using CoinJoin and their involvement with the Bitcoin Open Privacy Project. Wetouch on blockchain.com's approach to privacy and the legal status of coin join. The potential risks and complications involved in dealing with regulators are also discussed.

Topic: CoinJoin Sudoku - https://www.coinjoinsudoku.com/advisory/

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00:00 Introduction
01:15 Weekly recap. / Privacy principles.

02:51 How should we think about using anonymity networks?

03:42 A flawed implementation of Coinjoin.

04:26 Shared Coin (blockchain.info)

06:00 Coinjoin Sudoku.

07:14 Why was Shared Coin discontinued. / Regulatory concerns.

09:00 Joining transactions.

10:19 How good is the anonymity provided by the simple model?

10:47 Formal definitions.

12:01 Example of a breakdown of a Shared Coin transaction.

14:32 Discussion

14:56 Responsible disclosure process. / Boltzmann transaction analysis tool.

16:24 Combinations of subsets.

19:24 Matching heuristics.

21:00 Assumptions. / Shared Coin server parameters. / Plausible deniability.

24:20 An efficient algorithm for Coinjoin Sudoku for large transactions.

26:06 Discussion of example of Shared Coin transaction. / How Shared Coin works. / Users and service funds.

31:12 Fingerprinting the server's own funds.

32:17 The Bitcoin Privacy Project.

34:40 Is Blockchain's wallet aligned to your privacy concerns? / Lack of demand for privacy from users.

36:58 Fingerprinting of transactions.

40:38 Why is there confusion about legal status of the Coinjoin.

46:45 Bitcoin SX.

48:14 Conclusion.