Bitcoin Cash (BCH) development continues as software engineers have revealed two distinct concepts that aim to boost the BCH network. Bitcoin Cash developer Tom Zander has announced new documentation concerning the vision of double-spend proofs, which now exists as a pull request to the alternative BCH implementation Flowee the Hub. Additionally, Electron Cash developer Jonald Fyookball has reported on the expanded specifications for the Cashshuffle method Cashfusion, a scheme that adds higher levels of privacy to unlinkable coins.
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Cashfusion Specifications Enhanced
Developers put a lot of time and effort into creating applications and platforms that make Bitcoin cash easier to use, more secure, and sometimes more private. On Monday, Electron Cash and Cashshuffle developer Jonald Fyookball informed the BCH community that “Cashfusion got a whole lot better.” Cashfusion is an extension of Cashshuffle, the BCH shuffling application that doesn’t require a trusted third party. The application offers a superior anonymity set by obfuscating the relationship between the owner’s old and new BCH addresses within the shuffling process. To many BCH proponents, Cashshuffle is very good but the spectrum of privacy can be improved. For instance, if a user has mixed a bunch of coins and they eventually consolidate them into one address it can still leave behind some clues for blockchain analysis.
“We need a method to coordinate Coinjoin transactions with multiple inputs per user,” explains the Cashfusion specifications. “This is inherently challenging because we want to hide input linkages while simultaneously attempting to blame/ban users who don’t sign all their inputs.” However, Cashfusion proposes a blind verification scheme where each input and output is verified by a random Cashshuffle participant while also providing a series of cryptographic commitments than can identify and ban uncooperative participants. The Cashfusion author’s add:
CashFusion provides high levels of privacy via a flexible scheme that allows an arbitrary number of inputs and outputs of non-standard amounts. It provides anonymous, trustless coordination with usually zero-knowledge of linkages revealed to other players or the server.
Fyookball explained he’s been working with independent software developer Mark Lundeberg and has put “100+ revisions” into the project since he last updated the community. “The new scheme not only is more secure, but allows basically any number of inputs and outputs of any amounts — This means it can offer high levels of privacy with unlinkable coins,” Fyookball asserted. Cashshuffle has been an extremely popular application for BCH and so far, according to data stemming from Acidsploit’s Cashshuffle stats page, there’s been 116,438 BCH or more than $34 million at today’s BCH prices shuffled to date. There’s been a total of 21,336 shuffles mixing all those coins since March 27. Moreover, thanks to the release of the Cashshuffle JS library, other wallets like Bitcoin.com’s noncustodial wallet will provide Cashshuffle features as well.
On the same day, the software developer Tom Zander revealed the completion of a pull request to the alternative BCH implementation Flowee the Hub which aims to provide double-spend proofs (DSP). Essentially the concept of DSP documentation is authored by the developer Imaginary Username and the idea adds a fraud-proof system for double-spending. DSP was also adapted from Chris Pacia’s Double Spend Alert work and Mark Lundeberg has been contributing to the project. Zander said on Monday that the system they came up with is a “relatively small (constant size) message with actual proof that the spender signed two different transactions spending the money you were hoping to receive.” The software engineer added that the important aspect of DSP is to make sure an original double-spending transaction cannot be recreated. “Double spend proofs have been an idea for years, with lots of people talking about it and we had some initial specs and even a conference about this last year,” Zander told the BCH community.
“This document describes a new Bitcoin Cash network message that is generated when two transactions spending the same input are detected on a participating node, and related protocol to relay it through the network among participating nodes,” the specification explains on Github. “A transaction that has its inputs all being from P2PKH or P2SH-multisig outputs, follow prevailing standardness rules and has all signatures signed with SIGHASH_ALL without the ANYONECANPAY flag,” the developer’s data notes. And in the case of P2SH-multisig containing all unique pubkeys, is hereby referred to as ‘protected transactions.’”
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