Wasabi Research Club #12 - Why I'm not an Entropist with Harry Halpin
Channel: Wasabi Wallet
Date: 2020-03-24

Today our hosts and guest Harry Halpin discuss the concept of entropy and its role in quantifying anonymity in communication systems like Tor. They delve into the historical development of Tor and its goals, highlighting the debate around the effectiveness of mixing designs in achieving anonymity. The conversation also touches on the limitations and implications of using Tor and mixed networks, as well as the challenges of implementing decentralized systems and ensuring privacy in platforms like Bitcoin. They acknowledge the importance of entropy as a metric in anonymizing communications but emphasize the need for additional factors and a nuanced understanding of different threat models when assessing anonymity. The discussion showcases the complexities of measuring and achieving anonymity in practice and the continuous evolution of privacy-focused technologies.

Topic: Why I'm not an Entropist - https://www.freehaven.net/anonbib/cache/entropist.pdf
Guest: Harry Halpin

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00:00 Introduction. / Paul Syverson. / Entropist model for communications is broken.

02:32 Introduction to "Why I'm not an entropist." / Argument about how to build anonymous communications. / Why is an onion network better than a mix network? / Measuring anonymity.

12:50 Tor and entropy. / Defining anonymous communication. / Tor's threat model. / Anonymous communications aren't mathematically well-definable.

14:53 Entropy is not sufficient in quantifying anonymity. / Is the entropy the wrong metric.

16:25 Is entropy applicable to anonymising Coinjoins.

18:48 Entropy model for Coinjoins. / Boltzmann's entropy. / Shannon entropy.

21:05 Differentiation between types of entropy.

22:29 Definition of entropy.

24:14 Syverson's on entropy. / Global Passive Adversary. / Mixmaster anonymous remailer. / Active local attacks.

28:55 Onion routing in an entropist model.

32:02 Competing Sybils.

36:06 Access onion nodes vs accessing exit nodes. / Web browsing.

39:59 Deanonymisation. / Security of Tor hidden services.

40:48 3 categories of anonymous communication networks. / Dining Cryptographer network (DC-nets). / Decred.

42:46 Coinshuffle++.

46:40 What are people using that provides reasonable anonymity? / Monero. / Using exchanges.

47:57 Real world attacks on mixers and Monero. / Equal output Coinjoins. / Merging coins.

51:54 Round phases in a Coinjoin / Timeouts. / Slow users. / Is there any faster anonymity network than Tor. / metrics.torproject / Latency.

58:28 Changing Tor streams.

01:00:47 Non-malicious Tor exit nodes. / Non-KYC off-ramps.

01:02:06 Differentiating mixnets and onion routing.

01:05:37 The crypto community should be looking into anonymous communications. / Chainalysis running 10% of Bitcoin nodes.

01:08:50 Centralised backend servers vs decentralised Electrum servers.

01:09:36 Conclusion.