Wasabi Research Club #7 - CashFusion with Jonald Fyookball (Part 1)
Channel: Wasabi Wallet
Date: 18/02/2020

Today we introduce the topic of CashFusion and its purpose of allowing users to consolidate coins without revealing ownership. There is a discussion about the privacy concerns of coinjoining and the need for a private way to consolidate coins. Jonald Fyookball explains how CashFusion addresses these concerns by allowing users to participate in coinjoins without a coordinator and allowing for arbitrary inputs and outputs. The concept of tiers in CashFusion is also mentioned, as well as the multi-step process for transaction signing and verification. The potential risks of a malicious server and the use of hashing and salting in CashFusion are also discussed. The section concludes with a discussion on the trade-offs and challenges of implementing CashFusion. 

Topic: In this meeting we discussed CashFusion with one of the authors, Jonald Fyookball.

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00:00 Intro
00:50 Weekly recap.

01:15 CoinShuffle / CoinShuffle++.

02:25 The problem(s).

07:50 Introduction to CashFusion.

08:52 Origins of CashShuffle.

10:42 Does CashFusion defend against subset-sum analysis of change.

12:14 Combinatorics of CashFusion.

14:45 Phase 1. Setup and waiting list. / Output tiers.

16:47 Equal amounts vs a range in CashFusion.

17:44 Phase 2. Starting the round. / What should the nonce be?

20:48 Why do you need different locations when using Tor streams?

22:27 Would that lead to cross-referencing between rounds?

24:24 Will the server know in which rounds a player participated over multiple rounds?

26:18 Timeout periods.

28:00 Wasabi initiation.

29:30 Phase 3. Commitments.

32:32 Phase 4. What is blinded?

34:06 Phase 5. Covert announcement of inputs and outputs.

36:00 Phase 6. Sharing components.

37:17 Phase 8. Executing the transaction. / Blame phase.

40:23 Design tradeoffs.

42:13 Implementation, speed, and scaling.

44:29 Parallel vs sequential. / Participants offline.

45:52 Publishing and collaborating on Github.

47:44 Summary.

49:20 In the worst case during the blame phase, who learns what about the other participants?

51:49 Malicious user coordinating with malicious server.

53:12 Conclusion.

54:10 Topics for next week.

56:55 CoinShuffle++. How does a Dining Cryptographer (DC) network avoid collisions.