Published on: 2016-08-10T07:53:01+00:00
In a 2016 email thread, James MacWhyte discusses the potential need for verification by miners to protect against duplicate spends. He mentions a scenario where Alice sends Bob a transaction and Timothy broadcasts a transaction with a random hash that references the same output. Miners are unable to verify if this is valid, resulting in Bob's money becoming useless. MacWhyte explains that a duplicate spend proof must be signed by the same user (Alice) to be considered a double spend.A new proposal has been put forward to hide the entire content of bitcoin transactions. This goes beyond previous privacy measures such as CoinJoin, ring signatures, and Confidential Transactions. The idea is to publish only the hash of inputs and outputs in the blockchain as OP_RETURN, while hiding the entire inputs and outputs. To prevent double-spends, the payer must also publish another hash known as the spend proof, which is the hash of the output being spent. The proposal suggests using a new private coin called Black Bitcoin or BBC, which can be obtained by burning regular BTC. Private transactions would require one input, one previous output, and every output would include a blinding factor.The proposal acknowledges that larger outputs may need to be split into smaller ones, and more inputs may need to be combined when sending large amounts. This could potentially cause privacy leakage, but it can be avoided by using multiple addresses and storing smaller amounts on each address. Exchanges and large merchants may accumulate large coin histories, which should be kept in mind.No hard or soft fork is required for the proposed privacy-preserving currency, BBC. It operates on top of the bitcoin blockchain using the same private keys and addresses as BTC. Each BBC transaction must be enclosed in a small BTC transaction that stores the OP_RETURNs and pays for the fees. The proposal lacks encryption, so true privacy can only be achieved when using bitcoin over Tor.In a discussion on bitcoin transaction design, concerns were raised about the proposed design of hiding entire inputs and outputs. James MacWhyte pointed out that users would need to back up entire histories of every output sent to them, rather than just backing up a single private key. Additionally, being online to receive payments could pose challenges in sending the private message containing the coin's history. Tony Churyumoff suggested using hubs to route end-to-end encrypted messages to address these concerns.Peter Todd responded to a proposal made by James MacWhyte, stating that while verifying transactions is important, preventing double-spending is a fundamental requirement of Bitcoin. He mentioned his own proposal from 2016, which focused on closed seal sets and truth lists for privacy without sacrificing the ability to prevent double-spending.
Updated on: 2023-08-01T18:52:45.059568+00:00