@nyusternie 11 June 2020 edited more from that month

To Shuffle OR Fuse? Why Not BOTH?

This is a question I've been asking myself for months now. At first it naturally made sense to focus on **CashFusion**, as it was the successor to **CashShuffle**. However, I could never accept the fact that CashFusion required TOR, which restricted its use to desktop and native apps. For that reason, **I've been pursuing a more collaborative solution, which I'd like to share now.** https://cashfusion.org https://cashshuffle.com As you probably already know, CashFusion successfully funded their security audit by the same company that performed the **audit for CashShuffle.** As much as I would've preferred to wait until AFTER the audit report to critique the protocol, I honestly have no idea what's taking so long; and I'd like to keep things movin'... https://research.kudelskisecurity.com/2019/03/27/audit-of-cashshuffle/ A Quick Intro Both of these privacy protocols aim to provide greater anonymity for Bitcoin Cash users, by collectively mixing *(shuffling & fusing)* user's coins together in a **trustless** manner. The purpose is to remove any "taint" that may exist **(knowingly or not)** and provide you the maximum fungibility of your digital money. Sounds great!

The Pros **FAST! FAST! FAST!** In testing, I've routinely completed shuffles in **less than 5 seconds.** That's from pool registration on the server to coin delivery in my wallet. **Works in ANY mobile or desktop web browser** This is a big adoption advantage, and this convenience factor should not be underestimated. Also, it should not go unnoticed that to currently use CashShuffle, you need to install a "desktop" application. — **see** **https://app.nitojs.org** **for a working web demo (in Alpha release)** The Cons **Cannot create larger coins** This is "The Problem", and the reason for developing CashFusion. My Recommendations **Why not server-less?** This is something that I've been working on since I started with the protocol back in January. I believe that by using **pub-sub messaging**, specifically **OrbitDB**, it would be possible for the pool players to manage their rounds **100% peer-to-peer.** Without any central servers, there's literally no one to shutdown; very similar to BitTorrent. https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern https://orbitdb.org/ **Dynamic pool size** I'd really like to see the ability to add more than 5 players per round. One thought would be, upon reaching 5 players, to have a delay before the start of the round of say 30 seconds to add additional players *(up to some limit)*.

The Pros **Can covertly take ANY size input(s) and covertly produce ANY size output(s)** There's simply no reason NOT to pop the champaign (sic) for this universally recognized, outstanding achievement that has eluded the entire crypto community for nearly a decade. The Cons **Cannot run on iOS devices** Mobile-first! That really should've been the first thought when designing this protocol. Background processes are **VERY** **restrictive** **on iOS****;** so there's NO way to natively run this protocol on ANY device. Message notifications, using a centralized service, is an option, but that has its own limitations and trade-offs. https://apple.stackexchange.com/questions/252239/do-ios-apps-run-in-the-background https://apple.stackexchange.com/a/252247 **Kinda sllooowwww...** The minimum time to complete a fusion is approx. 6 minutes. In my 6+ weeks of testing, the "average" time *(see #5)* was about an hour. **Requires TOR for covert server communications** This is only an issue if you desire web browser access to CashFusion. ***NOTE:*** *All desktop and native mobile apps support TCP.* **Too many tiers** There are currently 48 individual tiers to choose from. In comparison, CashShuffle has 8. This creates a problem *(see #5).* **Lower value tiers have very little liquidity** If you're planning to fuse anything under 1 BCH, you're likely going to wait several hours, if not days. My Recommendations **Add an alternative covert messaging channel** Pub-sub (aka **gossip protocol**) would not only enable browser-based compatibility, but would likely simplify integration for BCH wallet developers. ***NOTE:*** *After testing several gossip networks; imo, none were quite production-ready, but I feel this is worth further investigation and possibly warrants infrastructure investment.* https://en.wikipedia.org/wiki/Gossip_protocol **Reduce the number of tiers** I don't really understand the maths behind the reasoning for the 48 tiers *(****Resistor "E series" values****)*, but this needs to be seriously looked in to, for the sake of improving the overall liquidity and usability. https://en.wikipedia.org/wiki/E_series_of_preferred_numbers

Best Of Both Worlds So, finally to the jist of this article. Why not enhance the benefits of both protocols while minimizing their weaknesses? I don't have any flow diagrams, so I'll just do my best to explain. All coins *(UTXOs)* would start with a CashShuffle round. ***NOTE:*** *There's an 80% chance that your shuffle will have change.* If your coin is shuffled to a "desirable" size *(value)*, then you keep it *(ie. freeze it)*. If it's shuffled down to an "undesirable" size *(value)*, then you queue it for CashFusion. ***NOTE:*** *There's NO way to know what size coin you will receive until after the shuffle round is completed.* You can repeat this process over an over, "freezing" the coins you want and "queuing" the coins you don't. At some point you won't be able to shuffle any more coins; you would then request all of your "queued" coins be fused together into a single large coin *(or multiple coins)*; and *(optionally)* start the shuffle process all over again. *There's a bit more to it than this, particularly on the CashFusion side, but then the maths gets way over my head, so hopefully you have the basic idea.* A Final Point By using the above system, it might then make sense for CashFusion to **normalize its outputs** to match CashShuffle, ie. 0.0001 BCH through 1,000 BCH. The advantage would be that you could have less tiers *(perhaps even* ***just one large tier****, or dynamically generated tiers),* which would more easily mask the outliers. By the way, in case you missed it up above, and for those that haven't heard already, you can now **CashShuffle your coins from ANY mobile or desktop web browser using** **https://app.nitojs.org****.** Happy Shufflin' **😉**